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  • General Chemistry  (1,656)
  • Organic Chemistry  (965)
  • Inorganic Chemistry  (567)
  • 1995-1999  (3,188)
  • 1995  (3,188)
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  • 1995-1999  (3,188)
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  • 101
    Electronic Resource
    Electronic Resource
    Synthesis of (+)-Multifidene (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 447-451 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (+)-Multifidence ((+)-1) has been synthesized starting from (R)-(cyclopent-2-enyl)methanol ((+)-2) via its chloroformate 4, Co-mediated radical cyclization reaction to the lactone (+)-6, and introduction of the olefinic side chains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780215
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  • 102
    Electronic Resource
    Electronic Resource
    Biosynthetic Production of [N2,1,3,7,9-15N]Guanosine and [1,3,7,9-15N]inosine and conversion into [N6,1,3,7,9-15N]adenosine for structure elucidation of RNA by heteronuclear NMR (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 421-439 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure was developed for the biosynthetic preparation of 15N-labelled guanosine and inosine through the action of a mutant Bacillus subtilis strain. Crude [N2,1,3,7,9-15N]guanosine and [1,3,7,9-15N]inosine were isolated from the culture filtrate by precipitation and anion-exchange chromatography (Scheme 1). No cell lysis and no enzymatic degradation was necessary. The per-isobutyrylated derivatives 1 and 2 were isolated from a complex mixture, purified by virtue of their different lipophilicity, and separated in three steps involving normal-and reversed-phase silica-gel chromatography. One litre of complex nutrient medium yielded 8.44 mmol of guanosine derivative and 2.84 mmol of inosine derivative with high average 15N enrichment (83.5 and 91.9 atom-%, resp.). [N6,1,3,7,9-15N]Adenosine (4) was obtained from 2′,3′,5′-tri-O-isobutyryl[1,3,7,9-15N]inosine (1) through the ammonolysis of its 1,2,4-triazolyl derivative with aqueous 15NH3 (Scheme 2).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780213
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  • 103
    Electronic Resource
    Electronic Resource
    The Decomposition of cis-Fused Cyclopenteno-1,2,4-Trioxanes induced by Ferrous Salts and some oxophilic reagents (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 452-458 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two cis-fused cyclopenteno-1,2,4-trioxanes, 1a and 1b, were subjected to Zn in AcOH or FeCl2 · 4H2O in MeCN. In the first case, the main course was deoxygenation to give cyclopentanone (18) and the 1,4-diphenyl- or 1,4-bis(4-fluorophenyl)cyclopent-3-ene-1,2-diol 10 (Scheme 5). In the second case, isomerization chiefly occurred resulting in the formation of a dimer 9 of the respective 3,5-diaryl-5-hydroxycyclopent-2-enyl 5-hydroxypentanoates 8 (Scheme 3).
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780216
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  • 104
    Electronic Resource
    Electronic Resource
    Enantioselectivity and cis/trans-Selectivity in Dirhodium(II)-Catalyzed addition of diazoacetates to olefins (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 459-470 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Rh11-catalyzed carbenoid addition of diazoacetates to olefins was investigated with [Rh2{(4S)-phox}4] (1;phox = tetrakis[(4S)-tetrahydro-4-phenyloxazol-2-one]), [Rh2{(2S)-mepy}4] (2; mepy = tetrakis[methyl (2S)-tetrahydro-5-oxopyrrole-2-carboxylate]), and [Rh2(OAc)4] (3). While catalysis with 2 and 3 afford preferentially trans-cyclopropanecarboxylates, the cis-isomers are the major products with 1. In general, the enantioselectivities achieved with 1 and 2 are comparable. Additions catalyzed by 1 are strongly sensitive to steric effects. Highly substituted olefins afford cyclopropanes in only poor yield. The preferential cis-selectivity observed in reactions catalyzed by 1 is attributed to dominant interactions between the ligand of the catalyst and the substituents of both olefin and diazoacetate, which overrule the steric interactions between olefin and diazoacetate in the transition state for carbene transfer.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780217
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  • 105
    Electronic Resource
    Electronic Resource
    Ein neuer Zugang zu 2′-O-Alkylribonucleosiden und Eigenschaften deren Oligonucleotide (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 486-504 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A New Access to 2′-O-Alkylated Ribonucleosides and Properties of 2′-O-Alkylated OligoribonucleotidesA general access to 2′-O-alkylated ribonucleosides using the key intermediate 5 is presented. The incorporation of 2′-O-‘ethyleneglycol’- and 2′-O-‘glycerol’-substituted (i.e., 2′-O-(2-hydroxyethyl)- and 2′-O-(2,3-dihydroxypropyl)-substituted) ribonucleosides into oligonucleotides affords a new generation of oligonucleotides with high affinity for RNA, high specificity, and increased nuclease resistance.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780219
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  • 106
    Electronic Resource
    Electronic Resource
    Structure-Lipophilicity and Structure-Polarity relationships of amino acids and peptides (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 471-485 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The objectives of this study were to gain insights into the structure-lipophilicity relationships of peptides and to propose an improved model for estimating their lipophilicity. First, existing databases were extended to obtain the distribution coefficients of a total of 208 free or protected peptides (di- to pentapeptides). The polarity parameters (Λ) of 23 free amino acids and 19 protected amino acids (AcNH—CHR—CONH2) and of their side chains were calculated from experimental distribution coefficients and computed molecular volumes. An analysis of the polarity parameters revealed that the hydrophobicity of the amino-acid side chains is largely reduced due to the polar field of the backbone. The polarity parameters of the peptides were then obtained in a similar manner and shown to be highly correlated with the sum of the polarity parameters of their side chains, i.e., the lipophilicity of peptides can be calculated from their molecular volume and the sum of their side-chain polarities using the regression established for each individual series of peptides (Fig. 1). This last restriction is essential since the polarity and lipophilic increment of a NH—C*H—CO unit were shown to decrease with increasing length of backbone.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780218
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  • 107
    Electronic Resource
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    Mitteilungen (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 533-536 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780222
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  • 108
    Electronic Resource
    Electronic Resource
    Synthesis of Spiro[cyclohexane-1,2′-[2H]indene] derivatives as inhibitors of steroid 5α-reductase (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 857-865 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The spiro[cyclohexane-1,2′-[2H]indene] derivatives 15a,b with molecular dimensions and nucleophilic functional groups similar to known steroid 5α-reductase inhibitors (e.g. 2) were synthesized. The spiro[cyclohexane-1,2′-[2H]indene]-1′(3′H),4-dione (5) was synthesized from 5-methoxyindan-l-one ( = 2,3-dihydro-5-methoxy-1H-inden-1-one). A Grignard reaction and a dehydration step led to the cyclohexene (±)-7 which, upon a stereoselective hydrogenation catalyzed by Raney-Ni under mild conditions, gave 8a as a pure epimer. Further hydrogenation and hydrogenolysis of 8a over Pd/C at room temperature reduced the keto group to give pure 9a. Finally, the 5′-substituted derivatives 12a, 14a, and 15a were generated by deprotection and Heck-type reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780407
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  • 109
    Electronic Resource
    Electronic Resource
    Enantioselective Alternating Olefin-Carbon Monoxide Copolymerization: A new concept for activity and stereoselectivity (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 883-886 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cationic Pd-complexes modified by dicyclohexyl{(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyl}phosphine (1a) give very active catalytic systems for the regioregular isotactic specific copolymerization of propene with CO. Other alk-1-enes also give stereoregular and regioregular copolymers, even if with lower productivity. The copolymers are isolated as poly(4-alkyl-tetrahydrofuran-2,2,5,5-tetrayl-2-oxy-2-methylenes) B in the solid state and give the isomeric poly(2-alkyl-1-oxopropane-1,3-diyls) A by dissolution in (CF3)2CHOH. Solid polymer A (R = Et) is formed back at least partially when the dissolved material is reprecipitated from MeOH. The use of the related (ferrocenyl)diphosphine ligands 1b-e and 2 as the catalyst modifier shows that the presence of both elements of chirality and of large substituents on the P-atoms of the ligand is necessary to achieve good stereocontrol, and that the large difference in basicity between the two P-atoms is probably the reason for the good catalytic activity.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780410
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  • 110
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    Bortrifluorid-katalysierte Umsetzung von 3-Amino-2H-azirinen mit Amiden: Bildung von 4,4-disubstituierten 4H-ImidazolenHerrn Prof. Dr. Richard Neidlein zum 65. Geburtstag gewidmet (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 899-909 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Boron Trifluoride Catalyzed Reaction of 3-Amino-2H-azirines and Amides: Formation of 4,4-Disubstituted 4H-ImidazolesReaction of trifluoroacetamide and 3-amino-2H-azirines 1 in refluxing MeCN affords 4-amino-2-(trifluoromethyl)-4H-imidazoles 5 in fair yields (Scheme 3). Less acidic amides do not react with 1 under similar conditions. Therefore, a procedure involving BF3-catalysis has been elaborated: the aminoazirine 1 in CH2Cl2 at -78° is treated with BF3 · Et2O and then with a solution of the sodium salt of an amide in THF, prepared by addition of sodium hexamethyldisilazane at -78°. The 4H-imidazoles of type 5 are formed in ca. 50% yield (Scheme 4). Reaction mechanisms for this ring enlargement of 1 are proposed in Schemes 5 and 6.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780413
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  • 111
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    Functionalized Nitroalkanes in Organic Synthesis. The first concise preparation of 4-hydroxyheptadecan-7-one and 14-hydroxyoctadecan-8-one, two new hydroxy ketones isolated from Chiococca alba (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 879-882 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 4-hydroxyheptadecan-7-one (1) and 14-hydroxyoctadecan-8-one (2), two new hydroxyketones isolated from leaves of Chiococca alba, were synthesized, for the first time, by hydroxy-functionalized nitroalkanes 4 and 9, respectively, via two chemoselective key steps: i) nitroaldol condensation with basic alumina, and ii) direct Nef conversion of nitroalkenes to carbonyl derivatives with sodium hypophosphite, in order to preserve the OH group.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780409
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  • 112
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    Elektronentransfer und Ionenpaar-Bildung. 40. Mitteilung39. Mitteilung:[1]. Teil der Dissertation von C.A. [2].. Einkristall-Struktur von Bis(Natrium-1,1′-Biphenyl-2-thiolat-Diglyme): Ein Zwischenprodukt der reduktiven Ringöffnung von Dibenzothiophen (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 866-878 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron Transfer and Ion Pair Formation Single Crystal Structure of Bis(sodium 1,1′-biphenyl-2-thiolate-diglyme): An Intermediate in the Reductive Ring Opening of DibenzothiopheneOn Na-metal reduction of dibenzothiophene, the five-membered sulfur ring opens to form a colorless 1,1′-biphenyl-2-thiolate sodium salt, which, according to its single-crystal structure determination, is a dimer containing a four-membered, twice diglyme-solvated ring (diglyme···Na⊕⊖SR)2. Additional measurements provide the following information: cyclic voltammetry in aprotic MeCN solution shows one quasi-reversible electron transfer at E1/2Red = -2.58 V. The dibenzothiophene radical anion can be generated in aprotic THF solution at a K mirror and characterized by an 81-line ESR spectrum and its simulation. This blue species is also the first UV/VIS detectable one before the solution changes via green (due to blue + yellow color mixing) to yellow, yielding across an isosbestic point a second and diamagnetic compound. All of the above results suggest a consecutive two-electron reduction followed by an intersystem protonation, M + (e⊖) → M.⊖ (blue) + (e⊖) → (M⊖⊖, yellow?) + (H⊕) → MH⊖ (colorless), to yield the crystallized and structurally characterized reaction intermediate. The diglyme-solvated sodium-salt dimer provides a basis for a quantum-chemical discussion of some facets of the most likely microscopic reduction pathway.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780408
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  • 113
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    Absolute Rate Constants for the Addition of Benzyl (PhĊH2) and Cumyl (PhĊMe2) Radicals to Alkenes in Solution (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 910-924 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Absolute rate constants and their temperature dependence were determined by time-resolved electron spin resonance for the addition of the radicals PhĊH2 and PhĊMe2 to a variety of alkenes in toluene solution. To vinyl monomers CH2=CXY, PhĊH2 adds at the unsubstituted C-atom with rate constants ranging from 14 M-1S-1 (ethoxyethene) to 6.7 · 103 M-1S-1 (4-vinylpyridine) at 296 K, and the frequency factors are in the narrow range of log (A/M-1S-1) = 8.6 ± 0.3, whereas the activation energy varies with the substituents from ca. 51 kJ/mol to ca. 26 kJ/mol. The rate constants and the activation energies increase both with increasing exothermicity of the reaction and with increasing electron affinity of the alkenes and are mainly controlled by the reaction enthalpy, but are markedly influenced also by nucleophilic polar effects for electron-deficient substrates. For 1,2-disubstituted and trisubstituted alkenes, the rate constants are affected by additional steric substituent effects. To acrylate and styrenes, PhĊMe2 adds with rate constants similar to those of PhĊH2, and the reactivity is controlled by the same factors. A comparison with relative-rate data shows that reaction enthalpy and polar effects also dominate the copolymerization behavior of the styrene propagation radical.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780414
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  • 114
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    Lacton-Bildung durch ringerweiternde Fragmentierung von Epoxycyclodecanon-DerivatenHerrn Prof. Iliya Ognyanov zum 70. Geburtstag gewidmet (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 925-934 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lactones from Epoxycyclodecanone Derivatives by Ring Enlargement Involving Fragmentation ReactionsA stereospecific ring-enlargement reaction of alkyl esters of 2,3-epoxy-1-(3-hydroxypropyl)-10-oxocyclo-decanecarboxylic-acid derivatives is described, involving Grob fragmentation of in situ formed hemiacetals. The assignment of the relative configuration of the starting materials was accomplished on the basis of 1H-NMR data. The rearrangement of the epoxides 9 and 10 (with cis-orientation of the ester group and the epoxide ring, Scheme 1) gives the lactone 15 as the single and as the major product, respectively, with (Z)-configuration of the newly formed C=C bond. A concerted reaction mechanism is assumed. The formation of a small amount of 12 from 10 is probably due to a competitive two-step carbanion pathway. The reaction of the diastereoisomers 7 and 8 leads to the lactones 11 and 12, respectively, as the only ring-enlargement products (Scheme 1), with (E)-configuration of the newly formed C=C bond. On the basis of our results, we cannot distinguish in this case between a concerted and a two-step carbanion mechanism. This type of reaction takes place only in the presence of an ester group; no ring enlargement was detected in case of compound 20 (Scheme 3), which is the de(alkoxycarbonyl) derivative of 9. The eliminative opening of the epoxide ring in the epoxylactone 17 affords 11 as the single product (Scheme 2). A carbanion mechanism was assumed for this reaction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780415
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  • 115
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    O-(1-Phenyl-1H-tetrazol-5-yl) Glycosides: Alternative synthesis and transformation into glycosyl fluorides (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 959-969 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of new glycosyl donors, O-(1-phenyl-1H-tetrazol-5-yl) glycosides, are prepared from the corresponding hemiacetals, commercially available 5-chloro-1-phenyl-1H-tetrazole (2), and tetrabutylammonium fluoride (Bu4NF) in either THF or DMF. The mild reaction conditions are compatible with a variety of protecting groups. The glycosyl donors are treated with hydrogen fluoride-pyridine complex (HF·py) to rapidly provide glycosyl fluorides in good-to-excellent yields, apparently by a (single or double) SN2 mechanism as studied by both 1H- and 19F-NMR spectroscopy. Under acidic conditions, glycosyl fluorides equilibrate partially or completely, equilibration requiring a large excess of HF · py.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780418
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  • 116
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    Enantioselektive Synthese von Allyl-, Propargyl- und 4-En-2-inyl-aminen durch 1,2-Addition von Organocer-Reagenzien an chirale Aldimine (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 970-992 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantioselective Synthesis of Allyl-, Propargyl-, and 4-En-2-ynyl-amines via 1,2-Addition of Organocerium Reagents to Chiral Aldehyde Imines(E)- and (Z)-Allyl-, propargyl-, and 4-en-2-ynyl-amines 5 and 14, useful bifunctional building blocks and of pharmaceutical interest, are synthesized in high enantiomeric purity (e.e. ≥ 97%). Key step is the diastereoselective 1,2-addition (d.e. 86 to ≥ 98%) of organocerium reagents to chiral α,β-unsaturated aldehyde imines 3 or 8 to produce adduct amines 4 and 9 (Schemes 1 and 4, resp.). The propargylamine 9 is a substrate for Pd-catalyzed coupling with alkenyl halides to produce the enynylamine 11a and the thienyl-substituted alkynylamine 11b. The chiral auxiliary (S,S)-2 is removed from 4 and 11 in 3 steps affording the title compounds 5 and 14. Diastereoisomer enrichment of the hydrochloride of 6 by crystallization is possible.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780419
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  • 117
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    High-Yield Syntheses of Sodium, Potassium, and Thallium Hydrotris[3,5-bis(trifluoromethyl)pyrazolyl]borates and the X-ray crystal structure of {hydrotris[3,5-bis(trifluoromethyl)pyrazolyl]borato} thallium(I) (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 993-1000 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An improved synthesis of 3,5-bis(trifluoromethyl)pyrazole (1) is described. This compound was used for the high-yield syntheses of the tris(pyrazoly1)borates Nd[HB(3,5-(CF3),-pz)3] (2a) and the corresponding potassium salt, 2b, starting from 1 and NaBH4 and KBH4, respectively. A convenient route to the corresponding thallium(I) salt, 2c, using thallium(I) acetate and either 2a or 2b in CHCI3, is also described. The sodium (3a), potassium (3b), and thallium (3c) salts of bis(pyrazolyl)borate [H2B(3,5-(CF3)2-pz)2]- were also prepared. The above pyrazolylborates were characterized by 1H-, 13C-, 19F-, and 11B-NMR spectroscopy. The X-ray crystal structure of the thallium derivative 2c was determined. The compound crystallizes in the monoclinic space group P21/m with a = 8.248(9) Å, b = 15.034(12) Å c = 9.243(8) Å, β = 100.10(7)°, Z = 2. The Tl-atom adopts a pyramidal geometry with respect to the three N-atoms. However, two TI-N distances (2.725(7) Å) are longer than the third (2.675(10) Å).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780420
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  • 118
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    exo/endo-Selectivity in the Reaction of ‘Bare’ FeO+ with Bicyclo[2.2.1]heptane (Norbornane) (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1013-1019 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ‘Bare’ FeO+ reacts in the gas phase with norbornane with collision efficiency, and the most prominent cationic products correspond to [FeC5H6]+ (32%), [FeC7H8]+ (19%), [FeC3H6O]+ (19%) and [FeC6H6]+ (14%), which are structurally characterized by ligand exchange as well as collision-induced dissociation experiments. Circumstantial evidence is provided which indicates that the complexes [FeC5H6]+, [FeC7H8]+, and [FeC6H6]+ originate from an Fe(norbornene)+ intermediate which itself is formed by elimination of H2O from the [FeO(norbornane)]+ encounter complex. Although the reactions are preceded and/or accompanied by partial H/D exchange, the isotope distribution in the productions clearly points to a preferential endo-attack of bare FeO+, with an endo/exo-ratio of ca. 10.3 and kinetic isotope effects kH/kD for the endo-abstraction of 2.4 and of 7.7 for approaching an exo-C—H bond. The preferred endo-approach of bicyclo[2.2.1]heptane by ‘bare’ FeO+ is in distinct contrast to the P-450-mediated or the iron(III)porphyrin-catalyzed hydroxylation of this substrate which favor reactions at the exo-face.
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    Synthesis, Structure, and Reactivity of Secosteroids Containing a Medium-Sized Ring. Part 36.Part 35: [1]. Transannular photocyclization of some unsaturated 5,10-secosteroidal ketones: A reevaluation (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1291-1297 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structures 9 and 8 are proposed for the single isolated irradiation product of 5-oxo-5,10-secocholest-1(10)-en-3α-yl acetate (6) [2] and for the minor product of irradiation of 5-oxo-5,10-secocholest-1(10)-en-3β-yl acetate (1) [3], respectively. These compounds are formed in an alternative reaction with respect to the originally observed intramolecular Paterro-Büchi photoprocess (transformation of 1 to oxetane 2). The formerly postulated ‘active’ conformations for 1 and 6 still allow explanation of their generation.
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    Bildung von 1,2,4-Trithiolanen in Dreikomponenten-Gemischen aus Phenyl-azid, aromatischen Thioketonen und 2,2,4,4-Tetramethylcyclobutanthionen: Eine Schwefel-Transfer-Reaktion unter Bildung von ‘Thiocarbonylthiolaten’ ((Alkylidensulfonio)thiolaten) als reaktive ZwischenstufenAnstelle von ‘Thiocarbonyl-thiolat’ werden häufig auch die Bezeichnungen ‘Thiocarbonyl-sulfid’, ‘Thion-S-sulfid’ und ‘Thiosulfin’ verwendet.Teilweise von G.M. anlässlich des ‘Sixteenth International Symposium on the Organic Chemistry of Sulfur’, in Merseburg, Juli 1994, vorgetragen.Herrn Professor Dr. Rolf Huisgen zum 75. Geburtstag Gewidmet (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1298-1310 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Formation of 1,2,4-Trithiolanes in Three-Component Reactions of Phenyl Azide, Aromatic Thiones, and 2,2,4,4-Tetramethylcyclobutanethiones: A Sulfur-Transfer Reaction to ‘Thiocarbonyl-thiolates’ ((Alkylidenesulfonio)-thiolates) as Reactive IntermediatesThe reaction of PhN3 and aromatic thioketones 18 (two-component reaction) at 80° yields only the corresponding imines 22, S, and N2. Under similar conditions, in the presence of sterically crowded 2,2,4,4-tetramethyl-cyclobutanethiones 19 (three-component reaction), 1,2,4-trithiolanes of type 20 are formed in good yields in addition to imines 22 (Scheme 4). In case of 19a and 19c (X = CO, CS), the symmetrical trithiolanes 21a and 21b, respectively, are also isolated. With 4,4-dimethyl-2-phenyl-1,3-thiazole-5(4H)-thione (24) instead of aromatic thioketone 18, imine 25, trithiolane 21a, and 1,4,2-dithiazolidine 26 are formed (Scheme 5). A reaction mechanism for the formation of 1,2,4-trithiolanes 20 and 21, including an S-transfer to generate ‘thiocarbonyl-thiolates’ 2b and/or 2c and 1,3-dipolar cycloaddition with a thioketone, is proposed in Scheme 7.
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    Syntheses and PE-Spectroscopic Investigations of 2,6- and 3,5-Bridged 1,4-Dimethylidenecyclohexanes (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 2011-2025 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three 1,4-dimethylidenecyclohexanes, bridged in the 2,6- and 3,5-positions by two ethano (4), one ethano and one propano (5), and two propano bridges (6) have been synthesized. The interaction of the two exocyclic methylidene groups has been investigated by He(I) photoelectron (PE) spectroscopy. It revealed a slightly larger energy difference (0.8 eV) for 4 and 5 as compared to the parent 1,4-dimethylidenecyclohexane (7) (0.7 eV). The interpretation of the PE spectra was based on the comparison with PE data of related systems and with the results of semiempirical calculations on 4-6.
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    Reactions of Diazo Compounds with Imines. Preliminary communication (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 2048-2052 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [Rh2(OAc)4]-catalyzed addition of methyl diazoacetate to N-benzylideneaniline (1a) afforded the imine cis-2 in 35% yield. Under catalysis by chiral RhII catalysts, however, only racemic 1a was produced, and the yield was low. In the presence of dimethyl maleate, aziridine formation was suppressed, and an intermediate ylide 6 was trapped as cycloadduct 7. No aziridines were obtained, however, from 1b, 1c, and 3. The iminium salt 8 reacted with (trimethylsilyl)diazomethane in the absence of [Rh2(OAc)4] via dipolar cycloaddition followed by extrusion of N2 to 10.
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    Oligosaccharide Analogues of Polysaccharides. Part 5. Studies on the cross-coupling of alkynes and haloalkynes (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 2053-2064 
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cross-coupling of the homopropargylic ether 1 and the halopropargylic ethers 2a and 2b was optimized, and aspects of the coupling mechanism were studied. Coupling promoted by Pd° and Cu1 in the presence of an amine yielded a mixture of the heterodimer 3 and the homodimers 4 and 5 (Scheme 1). Optimizations were first directed at suppressing homo-coupling. Homo-coupling is partially due to a H/I exchange (1 + 2a ⇌ 6 + 7) promoted by CuI and an amine. The exchange, but not the formation of homodimers, was largely suppressed in DMSO. The influence of phosphine ligands was also evaluated. Weaker σ-donors (with the exception of PPh3) lead to a faster coupling and to a higher ratio of hetero- to homodimers, with P(fur)3 leading to the cleanest reaction. Homodimers are also formed (together with I2 · (i-Pr)2NH) by reductive dimerization of the iodoalkyne 2a in the presence of [Pd2(dba)3], CuI, and (i-Pr)2NH. Bulky and acceptor-substituted amines reduced the extent of the dimerization of 2a, but the bulkiest amines did not promote coupling. Better results were obtained by using the bromoalkyne 2b. Neither dimerization of 2b, nor H/Br exchange between 1 and 2b were observed. Coupling of 1 and 2b was slower than the one of 1 and 2a, but gave higher yields of the heterodimer 3. The yield of 3 and the ratio of hetero-to homodimers was greatly improved by addition of LiI; no phosphine ligand is then required. While the oxidative addition of the iodoalkyne 2a to [Pd(PPh3)4] (2a → 8a) was rapid, the one of the bromoalkyne 2b was much slower and proceeded via the η2-complex 9 as evidenced by 1H-NMR spectroscopy. The rearrangement of 9 to the bromopalladium σ-complex 8b follows first-order kinetics (k = 0.014 min-1). CuBr greatly increased the rate of this rearrangement. LiI caused rapid substitution of Br by I in the Pd σ-complex (8b → 8a), but not in 9, nor in 2b. The σ-complex 8a did not react with the alkyne 1 in the presence of (i-Pr)2NH, unless CuI was added. The alkynes 10 or 1 did not react with CuI and either TMEDA or (i-Pr)2NH to yield detectable amounts of the Cu-acetylides 11 or 12. These observations are rationalized by the mechanism shown in Scheme 3, postulating the intermediacy of the binuclear alkyne-Pd-Cu complexes C and J, and some or all of E-H, and highlighting the role of CuI in this coupling.
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    Hetero-Diels-Alder Additions of α,β-Unsaturated-Acyl Cyanides. Part 3Part 1: [7], part 2: [8].. Syntheses of 3-bromo-2-ethoxy-3,4-dihydro-2H-pyran-6-carbonitriles, and about their transformation to 2-ethoxy-2H-pyrans (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 151-164 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cycloadditions of the α,β-unsaturated-acyl cyanides 1-3 with (Z)-or (E)-1-bromo-2-ethoxyethene (4) may be performed at moderate temperatures and provide in good yields the 3-bromo-2-ethoxy-3,4-dihydro-2H-pyran-6-carbonitriles 5-7, respectively (Scheme 1). Diastereoisomeric pairs of products result at room temperature merely from the ‘endo’- and ‘exo’-transition states; more complex mixtures appear above 60° as a consequence of (Z)/(E)-isomerization of 4. The relative stability of the anomers of 5 and 6 is explored by treatment with BF3·Et2O. Acid alcoholysis (MeOH or EtOH) of 5 leads to acetals 9a, b of 4-bromo-5-oxopentanoate. Alkyl (2Z,4E)-5-ethoxypenta-2,4-dienoates 12, 17, and 20, are formed in alcoholic alkoxide solutions from 5, 6, and 7, respectively, which is compatible with the intermediacy of 2-alkoxy-2H-pyrans and their valence tautomers, α,β-unsaturatedacyl cyanides. Methoxide addition to the CN group competes with dehydrobromination in case of 5; it leads to 3-bromo-3,4-dihydro-2H-pyran-6-carboximidate 13 (ca. 50% at -20°) which can be hydrolyzed to the methyl carboxylate 14. DBU (1,8-diazabicyclo[5,4,0]undec-7-ene) in benzene converts 5 to 6-ethoxy-2-oxohexa-3,5-dienenitrile (11), the ring-opening product of an obviously unstable 2-ethoxy-2H-pyran; the same reagent dehydrobrominates 6 to 2-ethoxy-4-methyl-2H-pyran-6-carbonitrile (15). HBr Elimination from 7 takes place with great ease in presence of pyridine, or even during chromatography on alumina, and leads to the stable ethyl 6-cyano-2-ethoxy-2H-pyran-4-carboxylate (18); this dimerizes at room temperature to give a 1:3 mixture of tricyclic adducts ‘endo’-21 and ‘exo’-21. The structure of the latter is established by an X-ray crystallographic analysis.
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    Absolute Rate Constants for the Addition of Cyanomethyl (·CH2CN) and (tert-Butoxy)carbonylmethyl (·CH2CO2C(CH3)3) radicals to alkenes in solution (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 194-214 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Absolute rate constants and their temperature dependence were determined by time-resolved electron spin resonance for the addition of the radicals ·CH2CN and ·CH2CO2C(CH3)3 to a variety of mono- and 1,1-disubstituted and to selected 1,2- and trisubstituted alkenes in acetonitrile solution. To alkenes CH2=CXY, ·CH2CN adds at the unsubstituted C-atom with rate constants ranging from 3.3·103 M-1S-1 (ethene) to 2.4·106 M-1S-1 (1,1-diphenylethene) at 278 K, and the frequency factors are in the narrow range of log (A/M-1S-1) = 8.7 ± 0.3. ·CH2CO2C(CH3)3 shows a very similar reactivity with rate constants at 296 K ranging from 1.1·104 M-1S-1 (ethene) to 107 M-1S-1 (1,1-diphenylethene) and frequency factors log (A/M-1S-1) = 8.4 ± 0.1. For both radicals, the rate constants and the activation energies for addition to CH2=CXY correlate well with the overall reaction enthalpy. In contrast to the expectation of an electro- or ambiphilic behavior, polar alkene-substituent effects are not clearly expressed, but some deviations from the enthalpy correlations point to a weak electrophilicity of the radicals. The rate constants for the addition to 1,2- and to trisubstituted alkenes reveal additional steric substituent effects. Self-termination rate data for the title radicals and spectral properties of their adducts to the alkenes are also given.
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    Oligosaccharide Analogues of Polysaccharides. Part 2. Regioselective deprotection of monosaccharide-derived monomers and dimers (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 177-193 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Me3Si—C(1) bond of the bis-(trimethylsilyl)ethynylated anhydroalditol 2 is selectively cleaved with BuLi to yield 3/4, while AgNO2/KCN in MeOH cleaves the Me3Si—C(2′) bond, leading to 5 (Scheme 1). Both Me3Si groups are removed with NaOH in MeOH (→ 7), the (i-Pr)3Si group is selectively cleaved with HCl in aq. MeOH ( →6); all silyl substituents are removed with Bu4NF ( →8). Acetolysis transformed 9 into 13, which was desilylated to 14, while thiolysis of 9 led to a mixture 11/12. The tetraacetate 14 has also been obtained from 9 via 10. Oxidative dimerisation of either 3 or 5, or of a mixture 3/5 yields only the homodimers 15 and 16 (Scheme 2); treatment of 16 with AgNO2/KCN yielded 17, deprotection proceeding much more slowly than the cleavage of the Me3Si—C(2′) group of 2. The iodoalkyne 20, required for the cross-coupling with 5 according to Cadiot-Chodkiewicz, was prepared by deprotection of 3/4 to 18, methoxymethylation (→19), and iodination. Cross-coupling yielded mostly 21, besides the homodimer 22. Similarly, cross-coupling of 20 and 23 (obtained from 5) led to 24 and 22. The structure of 24 was established by X-ray analysis (Fig.), showing a C(6)-C(5′) distance of 5.2 Å. The conditions for deprotecting 2 were applied to 21, and led to 25 (AgNO2/KCN), 26 (aq. NaOH), 27 (Bu4NF), and 29 (HCl/MeOH; Scheme 3). Attempted deprotection of the propargylic-ether moiety with BuLi, however, failed. The dimer 27 was further deprotected to 28. Acetolytic (Ac2O/Me3SiOTf) debenzylation of the dimer 30, obtained from 10, gave 31 (83%) which was deacetylated to 32 (Scheme 4). Cross-coupling of 5 and the bromoalkyne 33, obtained from 10, yielded 34; again, acetolysis proceeded well, leading to 35. The cellobiose derivative 38 was prepared from the lactone 36 via 37. The glycosidic linkage of 38 proved resistant to the conditions of acetolysis, leading to 39. Acetolysis of the benzylated thiophene 40 (from 30 with Na2S) yielded the octaacetate 41, but proceeded in substantially lower yields (50%).
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    Synthesis of 4,6,8-Trisubstituted Methyl Azulene-2-carboxylates (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 238-241 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that sodium (methoxycarbonyl)cyclopentadienide (1), which is easily accessible from sodium cyclopentadienide and dimethyl carbonate in THF, reacts with 2,4,6-trisubstituted pyrylium tetrafluoroborates 2a-d in boiling MeOH to afford the corresponding methyl azulene-2-carboxylates 4a-d in good yields. The corresponding 1-carboxylates 3 were not found (cf. Schemes 1 and 2).
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    Synthesis of Benz[a]azulenes Substituted at the Benzo Ring (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 231-237 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that the thermal electrocyclic ring-closure reaction of 1,2-di[(E)-prop-1-enyl]benzene to yield 2,3-dimethylnaphthalene (cf. Scheme 1) [10] can successfully be applied also to the synthesis of benz[a]azulenes (cf. Schemes 2 and 3). Starting materials are methyl 4,6,8-trimethylazulen-2-yl ketone (6) and the corresponding 2-carbaldehyde 5, which, in a Horner-Emmons reaction, are transformed into the (azulen-2-yl)-acrylates (E)-8 and (E)-7, respectively. Vilsmeier formylation of these compounds, followed by the Horner-Emmons reaction leads to the formation of the bisacrylates (E,E)-11 and (E,E)-12, respectively. In an alternative reaction, (E)-8, on treatment with dimethyl acetylenedicarboxylate (ADM) in the presence of [RuH2(PPh3)4], can be transformed into the methoxycarbonyl-substituted bisacrylates (E,E)- and (E,Z)-17. All three bisacrylates, on heating at 180-190° in p-cymene, undergo cyclization to yield the corresponding dihydrobenz[a]azulenes 13, 14, and 18, respectively, which could easily be dehydrogenated on heating in the presence of Pd/C. The new benz[a]azulenes 15, 16, and 19 are fully characterized.
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    NMR-Spectroscopic Investigations of Potentially Planarized NonafulvenesFulvenes, Fulvalenes, Part 68; Part 67: [1]. Part 66 (short communication): [2]. (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 215-230 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H- and 13C-NMR spectra of nonafulvene 1e and nonafulvenes 2 and 3 have been assigned, high-resolution 1H-NMR spectra of 2 (600 MHz, Fig. 3) and of 3 (400 MHz, Fig. 2) have been analyzed, and the data are compared with those of other nonafulvenes (Tables 1-6). Generally speaking, according to their spectroscopic behavior, four classes of nonafulvenes (A-D) may be distinguished (Fig. 1). The investigation shows that compounds 1e and 3 belong to class A, being characterized by 1H-chemical shifts around 6 ppm, strongly alternating 3J(H,H) and 13C chemical shifts in the range of 123 to 130 ppm, thus existing in the olefinic form with a non-planar nine-membered ring. On the other hand, 2 is the first nonafulvene of class D, being characterized by 1H chemical shifts in the aromatic range, large 3J(H,H) values of the same size, and 13C chemical shifts around 110 ppm. Since NMR parameters are virtually not influenced by temperature (-50° to 50°) or solvents, it is concluded that 2 exclusively exists in the dipolar structure 2± with a planarized nine-membered ring. According to Fig. 4, these classes (and their spectroscopic data) are linked by 10,10-bis(dimethylamino)nonafulvene (1c; and its temperature-dependent NMR parameters): for 1c, a temperature-dependent equilibrium 1c⇌1c± had earlier been established.
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    L-Phenylalanine Cyclohexylamide: A simple and convenient auxiliary for the synthesis of optically pure α,α-disubstituted (R)- and (S)-amino acids (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 563-580 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This work describes L-phenylalanine cyclohexylamide (5c) as a simple, cheap, and powerful chiral auxiliary for the synthesis of a series of optically pure α,α-disubstituted (R)- and (S)-amino acids of type 1, such as (R)- and (S)-2-methyl-phenylalanine (1a), (R)- and (S)-2-methyl-2-phenylglycine (1b), and (R)- and (S)-2-methylvaline (1c; Scheme 3). These amino acids were efficiently transformed into the suitably protected and activated amino acid building blocks (R)- and (S)-12b and (R)- and (S)-12c (Scheme 4) which are ready for incorporation into peptides by solution or solid-phase techniques. Based on the crystal structures of 6b, 6c, and 7a belonging to the diastereoisomeric peptides series 6 and 7, the absolute configurations of each member of the series were determined. β-Turn geometries of type II′ and I were observed for 6b and 7a, respectively, whereas 6c crystallized in an extended conformation. The impacts of side-chain variation on conformation and crystal packing of these triamides are discussed.
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    Lipophilic Functionalized Cobyrinic-Acid Derivatives. Part 1. Cobester α-monoacids (α,α,α,β,β,β-hexamethyl α-hydrogen Coα, Coβ-dicyanocobyrinates) (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 581-599 
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The four α,α,α, β,β,β,-hexamethyl α-hydrogen Coα, Coβ-dicyanocobyrinates 2b, d-f, with a free b-, d-, e-, and f-propionic-acid function, respectively, were prepared by partial hydrolysis of heptamethyl Coα, Coβ-dicyanocobyrinate (cobester; 1) in aqueous sulfuric acid. The cobester monoacids 2b, d-f were obtained as a ca. 1:1:1:1 mixture which was separated. The monoacids were purified by chromatography and isolated in crystalline form. The position of the free propionic-acid function was determined by an extensive analysis of 2b, d-f using 2D-NMR techniques; an analysis of the C,H-coupling network topology resulted in an alternative assignment strategy for cobyrinic-acid derivatives, based on pattern recognition. Additional information on the structure of the most polar of the four hexamethyl cobyrinates, of the b-isomer 2b, was also obtained in the solid state from a single-crystal X-ray analysis. Earlier structural assignments based on 1D-NMR spectra of the corresponding regioisomeric monoamides 3b, d-f (obtained from crystalline samples of the monoacids 2b, d-f) were confirmed by the present investigations.
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    1-Lithio-2,2-diphenyl-1-(phenylsulfonyl)ethen: Synthese und Kristallstruktur (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 615-618 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses and Crystal Structure of 1-Lithio-2,2-diphenyl-1-(phenylsulfonyl)etheneCrystals of [1-lithio-2,2-diphenyl-1-(phenylsulfonyl)ethene]- N,N,N′,N′ -tetramethylethylenediamine (2/2) (2) were prepared by addition of BuLi to 1,1-diphenyl-2-(phenylsulfonyl)ethene (1) in the presence of N,N,N′,N′ -tetramethylethylenediamine (TMEDA) at low temperature. The X-ray structure analysis shows a centrosymmetric dimer bridged over an eight-membered (Li—O—S—O)2 ring. There are no Li-C contacts to the C(α) atoms. Both Li cations are tetracoordinated via the sulfonyl O-atoms and the N-atoms of the TMEDA ligand. The X-ray structure analysis of 1,1-diphenyl-2-(phenylsulfonyl)ethene (1) also was determined to compare interatomic distances and angles.
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    Pteridines. Part CVIPart CV: [1].. Isolation and characterization of limipterin (1-O-(L-erythro-biopterin-2′-yl)-β-N-acetylglucosamine) and its 5,6,7,8-tetrahydro derivative from green sulfur bacterium Chlorobium limicola f. thiosulfatophilum NCIB 8327 (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 600-614 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new pteridine compound was isolated from green sulfur photosynthetic bacteria, Chlorobium limicola f. thiosulfatophilum NCIB 8327. The structure of this pterin derivative was established to be 1-O-(L-erythro-5,6,7,8- tetrahydropterin-2′-yl)-β-N-acetylglucosamine (1) from 1H-NMR and CD spectra as well as from various mass spectrometric techniques and chemical-cleavage techniques. Upon acid hydrolysis of 1, equimolar amounts of biopterin (2) and N-acetylglucosamine were produced. The structure of the hydrolysis product 2 was confirmed by comparing its NMR, UV, CD, and MS and its chromatographical behavior with those of an authentic specimen. N-Acetylglucosamine was identified by an enzymatic hydrolysis experiment as well as by NMR and thin layer chromatography. Electrospray (ES), fast-atom-bombardment (FAB), and thermospray (TS) mass spectrometry of 1 yielded an MH+ at m/z 441. Periodate-oxidation experiments of the intact molecule 1 and of its hydrolysis product 2 are consistent with the proposed structure. Differential I2 oxidation experiments with the native compound showed that the in vivo oxidation state of this pterin is its tetrahydro form. We propose the trivial name ‘limipterin’ for this new compound.
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    Synthesis, Characterization, and Electrochemical and Photophysical Properties of Rhenium(I) and ruthenium(II) complexes of 2,2′-bipyridine ligand functionalized β-cyclodextrins (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 619-628 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, characterization, and electrochemical and photophysical properties of the ReI and RuII complexes of permethylated β-cyclodextrins, functionalized on the primary face by a 2,2′-bipyridine ligand, are reported. For comparison, model compounds, in which the cyclodextrin was replaced by a Me group, were also prepared and their properties investigated.
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    3-(Prop-2-enylidene)azetidin-2-one Derivatives: Synthesis, structure, and formation of 3-spiro-β-lactams via Diels-Alder reactionsDedicated to Prof.Fritz Sauter, Wien, on the occasion of his 65th birthday (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 629-635 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of 3-silylated β-lactams (1) with α,β-unsaturated ketones give the propylidene-β-lactams 3 and the cycloalkenylidene derivatives 5. Structure and configuration are elucidated by spectroscopic methods, and the reactivity is discussed. While compounds 5 do not react with dienophiles, the (Z)-isomers of 3 are the favored substrates for Diels-Alder reactions yielding the spiro compounds 6 and 7.
    Additional Material: 3 Tab.
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    Oligosaccharides Related to Tumor-Associate Antigens. Part 4Part 3: [1].. Modeling of the terminal tetrasaccharide of an antigen recognized by the MBr1 antibody and of overlapping Di- and trisaccharide sequences (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 636-646 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational space of the tetrasaccharide α-L-Fuc-(1→2)-β-D-Gal-(1→3)-β-D-GalNAc-(1→3)-α-D-GallPr (3) and of some overlapping di- and trisaccharide sequences was investigated with the aid of molecular-mechanics energy minimizations, molecular-dynamics simulations, and 1H-NMR analysis. These investigations suggested that in compound 3 a certain rigidity of the first two glycosidic linkages (Fuc-Gal and Gal-GalNAc) is combined with the flexibility of the third one (GalNAc-Gal).
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    Synthesis of (±)-Pyrenolide B (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 663-669 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the synthesis of the title compound 12, the important intermediate 7 was obtained in good yield from the easily available ethyl 5, 5-ethylenedioxy-2-oxocyclohexane-1-carboxylate (1) via ring enlargement of the bicyclic enol ether 5 (Scheme). Its reduction (NaBH4 in EtOH) and subsequent protection with (t-Bu)Me2Si resulted in the highly functionalized ten-membered lactone 9. Introduction of the (Z)-configurated double bond, followed by deprotection and elimination of H2O, gave (±)-pyrenolide B (12) in 16% overall yield.
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    Masthead (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cber.19951280101
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    Tripodal Triamidostannates as Building Blocks in the Generation of Sn - M-Bonded Heterobimetallics (M = Fe, Ru) (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 29-34 
    Details
    ISSN: 0009-2940
    Keywords: Tripodal ligands ; Triamidostannates ; Metal-metal bonds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By in situ lithiation of the trifunctional amines H3CC(CH2NHSiMe3)3, PhC(CH2NHSiMe3)3, and HC{SiMe2NH(p-Tolyl)}3 and subsequent reaction with SnCl2 the corresponding triamidostannates were obtained. These were coupled with CpM(CO)2Cl (M = Fe, Ru) to yield the M - Sn-bonded heterobimetallics 9-14 of which H3CC(CH2NSiMe3)3SnFe(CO)2Cp (9) was characterized by a single-crystal X-ray structure analysis. Of the in situ-generated amidostannates only [HC{SiMe2N(p-Tolyl)}3Sn][Li(THF)3] (8) could be isolated as a uniform product and characterized analytically and spectroscopically.
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    The Structures of [X2Y—N—YX2]+ Cations (X = F, Cl; Y = S, Se). A Comparison of X-ray and ab Initio Studies[1] (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 35-40 
    Details
    ISSN: 0009-2940
    Keywords: Selenium-nitrogen compounds ; Sulfur-nitrogen compounds ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structures of cationic species of the series [X2Y—N—YX2]+ (X = F, Cl; Y = S, Se) have been computed ab initio using all electron treatments for first-row elements and sulfur and quasi-relativistic pseudopotentials for Se and Cl. Splitvalence basis sets with polarization and diffuse functions were employed. The MP2 results for the (non-isostructural!) cations [Cl2Se—N—SeCl2]+ (1: Cs) and [F2S—N—SF2]+ (2: C2v) are in excellent agreement with the experimental (X-ray) observations. Both structures represent local minima. A deeper minimum for either of the cations is represented by another C2v isomer which for crystal lattice energy reasons is stable in the isolated state only. The geometries of the hitherto unknown species [Cl2S—N—SCl2]+ (3) and [F2Se—N—SeF2]+ (4) have been assessed by ab initio HF calculations. In analogy to 2, cations 3 and 4 are predicted to prefer C2v symmetry. Therefore, 1 exhibits unusual structural features. According to strictly localized natural bond orbital analysis (NBO), the central nitrogen atoms in 1 and 2 possess two lone pairs of electrons (LP: one sp hybrid and one p orbital). The relatively short Se—N and S—N bond distances in 1 (1.741-1.760 Å) and 2 (1.551 Å) can best be attributed to LP(N)→s̰*(Y—X) negative hyperconjugation (1: Y = Se, X = Cl; 2: Y = S, X = F).
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    Die fördernde Rolle von Phosphinoester-Liganden bei der Synthese neutraler Carben-, Vinyliden- und Allenyliden-Ruthenium(II)-KomplexeHerrn Professor Hubert Schmidbaur zum 60. Geburtstag gewidmet. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 49-62 
    Details
    ISSN: 0009-2940
    Keywords: Ruthenium(II) complexes, octahedral ; Phosphino esters as mono- and bidentate ligands ; Fluxional behaviour ; Carbene complexes ; Vinylidene complexes ; Allenylidene complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vinylidene Transition-Metal Complexes, XXXV[1].  -  The Supporting Role of Phosphino Ester Ligands for the Synthesis of Neutral Carbene, Vinylidene and Allenylidene Ruthenium(II) ComplexesThe reaction of [RuCl2(PPh3)3] (1) with the phosphino esters iPr2P(CH2)nCO2R (2-4) leads to complete (n = 1; R = CH3, C2H5) or partial (n = 2; R =CH3) displacement of the PPh3 ligands and formation of the octahedral ruthenium(II) complexes [RuCl2{k2(P,O)-iPr2PCH2CO2R}2] (5, 6) and [RuCl2(PPh3){k(P)-iPr2PCH2CH2CO2Me}{k2(P,O)-iPr2PCH2CH2CO2Me}] (7). Treatment of 5 with LiBr and LiI affords the dibromo- and diiodoruthenium derivatives 8 and 9. While compound 5 reacts with CO and SO2 by cleavage of one Ru - O bond to yield the 1:1 adducts [RuCl2(L){k(P)-iPr2PCH2CO2Me}{k2(P,O)-iPr2PCH2CO2Me}] (10, 11), the reaction of the dibromo derivative 8 with CO in solution gives the dicarbonyl complex [RuBr2(CO)2{k(P)-iPr2PCH2CO2Me}2](13). If CO is passed over 8 in the solid state, the corresponding monocarbonyl compound 14 is formed. The hydridoruthenium(II) complex 16, which is obtained from equimolar amounts of [RuHCl(CO)(PiPr3)2] (15) and 2, reacts with HC≡CMe by insertion to give the vinyl derivative [RuCl{E - CH=CHMe}(CO)(PiPr3){k2(P,O)-iPr2CH2CO2Me}] (17). Treatment of 5 with HC̊' (R' = H, Me, tBu, Ph) and of 6, 8, 9 with HC≡CPh affords upon photochemical activation the octahedral vinylidene complexes [RuX2-(=C=CHR){k(P)-iPr2PCH2CO2R}{k2(P,O)-iPr2PCH2CO2R}] (18-21 and 23-25) in good to excellent yield. At room temperature, these compounds (with the exception of 25) are highly fluxional in solution. From 31P-NMR measurements, the free energies of activation ΔG
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    Reaktionen von R2Al—AlR2 (R = CH(SiMe3)2) mit Trimethylsilylazid  -  Insertion in die Al—Al-Bindung und Abbau zum trimeren Dialkylaluminiumazid (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 81-85 
    Details
    ISSN: 0009-2940
    Keywords: Aluminium-aluminium bond ; Insertion of trimethylsilyl azide ; Trimeric dialkylaluminium azide ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of R2Al—AlR2 (R = CH(SiMe3)2) with Trimethylsilyl Azide  -  Insertion into the Al—Al Bond and Formation of a Trimeric Dialkylaluminium AzideTetrakis[bis(trimethylsilyl)methyl]dialuminium(4) (1) reacts with trimethylsilyl azide under insertion of one nitrogen atom into the Al—Al bond. As shown by NMR spectra and crystal structure the product contains three and four coordinated Al atoms due to the coordination of the α-nitrogen atom of the azide group to one of the Al atoms. An electronically delocalized N3-system is formed with a N—N bond length of 132.0 pm and a bond order of 1.5 for both N—N bonds. With an excess of trimethylsilyl azide further reaction is observed only under mild irradiation conditions with an exchange of the azide group between Si and Al and formation of Me6Si2 and the dialkylaluminium azide 3, which is better synthesized by the reaction of Me3Si—N3 with Cl—Al[CH(SiMe3)2]2. The sterically highly shielded aluminium azide 3 is a trimer in the solid state showing a non-planar 12-membered Al3N9 heterocycle with short N—N bonds (114 pm).
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    URL: http://dx.doi.org/10.1002/cber.19951280112
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    Transition-Metal Complexes with the Novel Scorpionate Ligand Dihydrobis-(tetrazolyl)borate: Synthesis and Characterization of Infinite Two-Dimensional Metal-Ligand Frameworks and One-Dimensional Water SubstructuresDedicated to Professor Dr. Herbert Schumann on the occassion of his 60th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 323-328 
    Details
    ISSN: 0009-2940
    Keywords: Poly(azolyl)borates, metal complexes of ; Bis(tetrazolyl)borate, metal complexes of ; Metal-nitrogen coordination ; Coordination polymers ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dihydrobis(tetrazolyl)borate metal compounds of the composition [M(L)2{μ-H2B(CHN4)2}2]n for M = Mn, Fe, Co, Zn, Cd with L = H2O and for M = Cu with L = NH3 are obtained from metal salts and K[H2B(CHN4)2]. Single-crystal X-ray studies reveal the formation of two-dimensional rhombic grid sheets through the bridging action of the bis(tetrazolyl)borate ligands. Each metal atom is octahedrally coordinated with two trans L ligands and four H2B(CHN4)-2 nitrogen donors. Two additional, hydrogen-bonded water molecules occupy the rhombic openings in the compounds with M = Mn, Fe, Co, Zn, and Cd. The water of crystallization is held in place through hydrogen bonding from the water ligands and to the nitrogen atoms to give a substructure of parallel kinked water chains. Temperature-variable magnetic measurements show a Curie-Weiss behavior for the paramagnetic complexes with M = Mn, Fe, Co, and Cu.
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    New Organophosphorus Ligands: Cyclopropanation and Other Reactions of Cumulenes Bearing Diphenylphosphanyl Substituents (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 365-371 
    Details
    ISSN: 0009-2940
    Keywords: Cumulenes ; Butadienes ; Vinylcyclopropane ; Vinylidenecyclopropane ; Bicyclopropyl, phosphanyl-substituted ; Cyclopropanation ; Phosphane ligands ; Phosphane chalcogenides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrophosphorylation of 1,4-bis(diphenylphosphanyl)butadiyne with diphenylphosphane leads to the butadiene (Ph2P)2C=CH—CH=C(PPh2)2 (1). Treatment of 1 with dimethylsulfonium methylide gives the vinylcyclopropane (Ph2P)2C=CH—CH(CH2)C(PPh2)2 (2). Compound 2 reacts with aqueous hydrogen peroxide, elemental sulfur, or selenium to afford the tetrachalcogenides (Ph2XP)2C=CH—CH(CH2)C(PXPh2)2 with X = O (3), X = S (4), X = Se (5), respectively. While the tetraphosphane 1 and the vinyl-cyclopropane compound 2 cannot be converted into a bis-(cyclopropyl) compound with an excess of Me2S=CH2, the tetrasulfide 4 readily affords a mixture of (1R,1′R)-/(1S,1′S)-and meso-2,2,2′,2′-tetrakis(diphenylthiophosphinyl)-1,1′-bicyclopropyl (6, 7) in good yield. Treatment of 1,1,4,4-tetrakis-(diphenylphosphanyl)butatriene with dimethylsulfonium methylide leads to the vinylidenecyclopropane (Ph2P)2C=C=C(CH2)C(PPh2)2 (8). Compound 8 is converted into its tetrasulfide (Ph2SP)2C=C=C(CH2)C(PSPh2)2 (9) by treatment with elemental sulfur. The crystal structures of 1, 2, 4, 7, and 8 have been determined by single-crystal X-ray diffraction.
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    Mono- und Diferriophosphane und -thioxophosphoraneHerrn Professor Dr. Ekkehard Lindner zum 60. Geburtstag gewidmet. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 413-416 
    Details
    ISSN: 0009-2940
    Keywords: Ferriophosphanes ; Ferriophosphoranes ; Thioxophosphane ligand ; Decarbonylation reaction ; Sulfurization ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mono- and Diferriophosphanes and -thioxophosphoranesHerrn Professor Dr. Ekkehard Lindner zum 60. Geburtstag gewidmet.The substitution of organic substituents in phosphanes or thioxophosphoranes by the 17-electron fragments CpFe-(CO)2 (—Fp) leads to isolobal ferriophosphanes or -thioxophosphoranes. The mono- and diferriophosphanes FpnPPh3-n [n = 1 (3), 2 (4)] are obtained by deprotonation of the mono- and diferriophosphonium salts [FpnPPh3-nH]X [n = 1 (1), 2 (2)] with DBU. They are oxidized by sulfur giving the mono- and diferriothioxophosphoranes FpnPPh3-n(S) [n = 1 (5), 2 (6)]. Sulfide 5 arises also from the reaction of CpFe(CO)2Cl and Ph2PH(S)/DBU. The one-sided decarbonylation reaction of 6 leads to FpFp′PPh(S) (7, Fp′ = CpFeCO). The Fp substituents (17 electrons) in 3-7 coordinate as one-electron donors to the PhnP- or PhnP(S) units (n = 1, 2). The bridging functions in 4 and 6 are hitherto unknown. The molecular structures of the complexes 5-7 were determined by X-ray structure analyses.
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    About some Electrophilic Substitution Reactions with [(CF3S)3C+][AsF-6] (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 435-436 
    Details
    ISSN: 0009-2940
    Keywords: Trifluoromethylthio group ; Carbenium ions ; Diphenylmethane ; Dyes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tris(trifluoromethylthio)carbenium hexafluoroarsenate (1) reacts with N,N-dimethylaniline and anisole to form the corresponding diphenylmethanes 2, 3 with the SCF3 group at the methine carbon atom. During the reaction of 1 with benzene, compounds such as C6H5C(SCF3)3 and C6H5SCF3 are formed along with benzophenone, a product of hydrolysis of the diphenylmethane compound.
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    URL: http://dx.doi.org/10.1002/cber.19951280417
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    Synthesis and Structure of the First Dimetalated Diphosphane Disulfide [(η5-C5Me5)(CO)2FeP(H)(S)]2 (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 441-442 
    Details
    ISSN: 0009-2940
    Keywords: Diphosphane disulfides ; Metallophosphoranes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first transition metal derivative meso-[(η5-C5Me5)(CO)2FeP(H)(S)]2 (2) of the unknown diphosphane disulfide [PH2(S)]2 results from treatment of (η5-C5Me5)(CO)2FePH2 (1) with 1.5 equivalents of elemental sulfur. Compound 2 was characterized by means of spectroscopy (IR, 31P, 31P{1H}, 13C{1H}, 1H NMR) as well as X-ray diffraction analysis.
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    URL: http://dx.doi.org/10.1002/cber.19951280419
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    Preparation and Molecular Structures of Tetrahydrofuran, Diethylene Diglycol Dimethyl Ether and 18-Crown-6 Complexes of Strontium and Barium TetrahydridoborateDedicated to Prof. Dr. Nils Wiberg on the occasion of his 60th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 455-460 
    Details
    ISSN: 0009-2940
    Keywords: Strontium bis(tetrahydridoborate)-2 tetrahydrofuran, chain polymer of ; Strontium bis(tetrahydridoborate)-bis(diglyme) ; Barium bis(tetrahydridoborate)-bis(diglyme) ; Strontium bis(tetrahydridoborate)-1,4,7,13,16-hexaoxacyclooctadecane ; Metal-hydrogen-boron bridges ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The strontium and barium tetrahydridoborate complexes M(BH4)2 · 2 diglyme and M(BH4)2 · 18-crown-6 (M = Sr, Ba) have been prepared from the solvates M(BH4)2 · 2 THF by ligand displacement. 11B-NMR and IR data reveal strongly polar bonding of the BH4 groups to the metal centers, and X-ray structural analyses of the diglyme and crown ether compounds show molecular units in which the BH4 group is in contact via three H atoms with the metal center. In contrast, M(BH4)2 · 2 THF compounds are chain polymers in the solid state, and each metal center is surrounded by 2 THF molecules in trans position and four BH4- groups each of which forms bridges with two metal centers. Estimations of the effective radius for the BH4 group indicate a high polarity for the M-BH4 interaction.
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    Photochemische Reaktionen von Übergangsmetall-Organyl-Komplexen mit Olefinen, 1312. Mitteilung: Lit.Photochemisch induzierte [5+2],homo[5+21-Cycloaddition von 3-Hexin an Tricarbonyl(η5-2,4-cycloheptadien-l-yl)mangan (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 515-518 
    Details
    ISSN: 0009-2940
    Keywords: Manganese ; Cycloheptadienyl ; Alkyne ; [5+2],homo[5+2] Cycloadditions ; Tricyclo[5.3.1.04,10]undeca-2,5-dien-11-yl ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemical Reactions of Transition Metal Organyl Complexes with Olefins, 1312. Mitteilung: Lit. . - Photochemically Induced [5+2], homo[5+2] Cycloaddition of 3-Hexyne to Tricarbonyl(η 5-2,4-cycloheptadien-1-yl)manganeseTricarbonyl(η5-2,4-cycloheptadien-1-yl)manganese (1) reacts upon UV irradiation in hexane at 243 K with two equivalents of 3-hexyne (2) in successive [5+2],homo[5+2] cycloadditions to give tricarbonyl(η2:2:1-1,2,3,11-tetraethyltricyclo-[5.3.1.04,10]undeca-2,5-dien-11-yl)manganese (3). Its crystal and molecular structure was determined by an X-ray diffraction analysis, in solution it was studied also by IR and NMR spectroscopy.
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    Masthead (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280601
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    1,4,2-Diazaphospholothiazoles and -pyridines by a Hantzsch-Type Condensation Using Chloromethyldichlorophosphane (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 581-587 
    Details
    ISSN: 0009-2940
    Keywords: Anellated azaphospholes ; Hantzsch-type [3 + 2] cyclocondensation ; Chloromethyldichlorophosphane ; Regioselectivity ; 31P-, 1H-, 13C-NMR spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [3 + 2] cyclocondensation of 2-amino-1,3-thiazoline, 2-aminopyridines, 2- and 4-aminopyrimidines, 2-aminopyrazine, and 2-aminoquinoline with chloromethyldichlorophosphane in the presence of triethylamine yields regiospecifically 5,6-dihydrothiazolo[2,3-e][1,4,2]diazaphosphole (3), 1,4,2-diazaphospholo[4,5-α]pyridines (12), 1,4,2-diazaphospholo[4,5-α]pyrimidines (15), 1,4,2-diazaphospholo[4,5-e]pyrimidine (17), 1,4,2-diazaphospholo[4,5-α]pyrazine (19), and [1,4,2]diazaphospholo[4,5-α]quinoline (22), respectively. Using 2-amino-1,3-thiazole (4) and 2-aminobenzothiazoles 8, we obtained mixtures of the 1,5- and 4,5-anellated 1,4,2-diazaphospholes 5/6, 9a/10a and 9b/10b, while in the case of the methyl derivative 8c only the [1,4,2]diazaphospholo[5,4-b][1,3]benzothiazole 10c was formed. In the reaction of 2-aminothiazole and 2-aminopyrazine with Chloromethyldichlorophosphane the bis(diazaphospholo)-substituted chloromethylphosphanes 7 and 20 could be detected. The new anellated 1,4,2-diazaphospholes are colorless to pale yellow crystalline moisture-sensitive solids.
    Additional Material: 6 Tab.
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    Reactions at Silicon-Silicon Bonds, V. Selective Trichlorosilylation of Alkyl(diorganylamino)chlorophosphanes with Hexachlorodisilane or with Trichlorosilane/Triethylamine. - Two Routes to New Functional Trichlorosilylphosphanes (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 615-619 
    Details
    ISSN: 0009-2940
    Keywords: Reductive silylation ; Aminochlorophosphanes ; Silylphosphanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of alkyl(diorganylamino)chlorophosphanes R(R2′N)PCl 1 (1a: R = tBu, R′ = Et, 1b: R = iPr, R′ = iPr; 1c: R = iPr, R′ = Ph) with hexachlorodisilane, afforded alkyl(diorganylamino)trichlorosilylphosphanes R(R2′N)PSiCl3 2 (2a: R = tBu, R′ = Et; 2b: R = iPr, R′ = iPr; 2c: R = iPr, R′ = Ph) and silicon tetrachloride. An intermediate formed in the reaction of 1b with hexachlorodisilane, the adduct iPr(iPr2N)(Cl)P-Si(Cl)3-SiCl3 (3b = 1b · Si2Cl6), was detected by 31P- and 29Si-NMR spectra that indicate pentacoordinated silicon bound to tetracoordinated phosphorus and tetracoordinated silicon. Trichlorosilylphosphanes 2 are also available from 1 under very mild conditions by reductive trichlorosilylation with trichlorosilane in the presence of triethylamine. Compounds 2 were identified analytically, by mass spectroscopy, multinuclear NMR, and an X-ray structure determination of 2c.
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    Reactions of Complex Ligands, LXIVPart LXIII: Ref.. Synthesis of 5,5′-Diphenyl-2,2′-bifuran, a Biaryl Compound with Remarkable Fluorescence Properties (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 641-643 
    Details
    ISSN: 0009-2940
    Keywords: Carbene ligands ; Tungsten complexes ; 2,2′-Bifuran ; Copper coupling reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 2-oxacyclic α,β-unsaturated carbene complex 1 reacts with an excess of dimethylamine to give the diphenylbifuran 2. The structure of 2 was established by independent synthesis from 2-phenylfuran (4) via regioselective lithiation and transmetalation to zinc and tin organometallics 6a-c and final oxidative copper coupling reactions.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19951280618
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    Synthesis of 2- and 3-Stannolenes via Addition of Trimethyltin Alkoxides to 3-Diethylboryl-4-ethyl-1,1-dimethylstannole (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 679-687 
    Details
    ISSN: 0009-2940
    Keywords: Stannole, diethylboryl-substituted ; Trimethyltin alkoxides ; 2-, 3-Stannolenes, organometallic-substituted ; NMR, coupling constants, 2J(Sn,Sn), sign determination ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trimethyltin alkoxides (2) react stereoselectively with 3-diethylboryl-4-ethyl-1,1-dimethylstannole (1) via addition of the Me3Sn group to C(2) to the C(2) = C(3) bond and a 1,2 shift of an ethyl group from boron to C(3) to give the 2-stannolenes 3. The molecular structure of 3f' [R = (S)-2-Bu] was determined by single-crystal X-ray analysis, confirming the cis positions of the Et(RO)B and the Me3Sn group. These 2-stannolenes 3 undergo, upon heating to ca. 80°C, facile rearrangement by irreversible allylic migration of the Et(RO)B group to the 3-stannolenes 4 in which the cis positions of the boryl and the stannyl group are retained. All 2-stannolenes (in contrast to the 3-stannolenes) are readily deprotoborylated to give the 3-stannolene 5. The structures of 3, 4, and 5 follow conclusively from 1H-, 11B-, 13C-, and 119Sn-NMR spectra. The negative sign of the geminal coupling constants 2J(SnSn) was determined in the case of 3, 4, and 5 by 2D 119Sn/1H heteronuclear shift correlations.
    Additional Material: 3 Ill.
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    Synthesis of Structures of (Acyloxy)boranesDedicated to Prof. Dr. A. Schmidpeter on the occasion of his 65th birthday.Synthesis of Structures of (Acyloxy)boranes (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 751-762 
    Details
    ISSN: 0009-2940
    Keywords: Trifluoroacyloxy-9-borabicyclo[3.3.1]nonane ; Pivaloyloxy-9-borabicyclo[3.3.1]nonane dimer ; Bis(9-borabicyclo[3.3.1]nonyl]oxalate ; Tetrakis(9-borabicyclo[3.3.1]nonyl)-dihydroxyoxalate ; Bis(9-borabicyclo[3.3.1]nonyl)-2,2-dimethylmalonate tetramer ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 9-Borabicyclo[3.3.1]nonane (9-BBNH) reacts with monocarboxylic acids to afford 9-(acyloxy)-9-borabicyclo[3.3.1]nonanes which are dimers in the solid state as shown by X-ray crystal structures of the benzoate and pivalate. More complex reactions were observed by allowing 9-BBNH to react with dicarboxylic acids in THF or monoglyme. Thus, (9-BBN)2 oxalate 3 contains a fully delocalized oxalate unit with equal C-O and B-O bond lengths. Traces of water convert it into the tetrakis(9-BBN) oxalate 5. A rather unusual structure is veryfied by 9-BBN 2,2-dimethylmalonate 7 which according to its molecular structure is a tetramer featuring a 32-membered ring system. In contrast, reactions of oxalic acid with thexylborane leads to reduction of the acid and formation of a bicyclic dioxaborolo-dioxaborolane 10. Several intermediates were detected by 11B-NMR spectroscopy as well as in reactions of BH3 · THF or BH3 · SMe2 with oxalic acid.  -  It follows from the present study that (acyloxy)boranes derived from dicarboxylic acids are strong Lewis acids with an unexpected variety of structural features.
    Additional Material: 7 Ill.
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    A T-Shaped Selenenyl Halide: Synthesis and Characterisation of a Proposed Reaction Intermediate (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 741-742 
    Details
    ISSN: 0009-2940
    Keywords: Selenenyl halides ; Nucleophilic substitution ; Complex intermediate ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The T-shaped selenenyl halide (1), which may be regarded as a model substance for the transition state in nucleophilic displacement at divalent chalcogen atoms, has been isolated and subjected to X-ray structure determination.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19951280715
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    Zinc Complexes of Drugs Containing Nitrogen Heterocycles (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 779-785 
    Details
    ISSN: 0009-2940
    Keywords: Zinc complexes ; Drug ligands ; Captopril ; Isoniazid ; Nalidixic acid ; Mercaptopurine ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four drugs whose actions have a relation to the status of zinccontaining species in the human body were used as ligands in zinc complexes. Captopril (H2Cap) forms the compound [ZnCap] (1) presumed to be a coordination polymer with O and S coordination. Isoniazid, in the presence of zinc salts, is converted to 1,2-diisonicotinoyl hydrazide (H2Nih) which forms polymeric [Zn(Nih)NH3] (2) with trigonal-bipyramidal ZnO2N3 coordination. Nalidixic acid (HNal) and zinc perchlorate yield [Zn(HNal)2(H2O)2](ClO4)2 · 2 H2O (3) containing zinc in an octahedral ZnO6 environment. Mercaptopurine (H2Mer), in the presence of ammonia, forms [Zn(Mer)(NH3)2] . H2O (4) which is a coordination polymer containing tetrahedral ZnN4 units. The structures of [Zn(Nih)NH3], [Zn(HNal)2(H2O)2](ClO4)2 . 2 H2O, and [Zn(Mer)(NH3)2] . 2 H2O were determined diffractometrically.
    Additional Material: 4 Ill.
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    Enantioselective Deprotonation of Benzyl Phosphates by Homochiral Lithium Amide Bases  -  Configurational Stability of Benzyl Carbanions with a Dialkoxyphosphoryloxy Substituent and Their Rearrangement to Optically Active α-Hydroxy Phosphonates (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 823-830 
    Details
    ISSN: 0009-2940
    Keywords: Phosphate-phosphonate rearrangement ; Carbanions, benzylic, configurational stability of ; Phosphonaes Lithium amides, homochiral ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Benzyl dialkyl phosphates are deprotonated enantioselectively by homochiral lithium amides of isopropyl(1-phenylethyl)amine or bis(1-phenylethyl)amine. The short-lived benzylic carbanions formed are virtually configurationally stable relative to the rearrangement to optically active phenyl-hydroxymethylphosphonates. The enantiomeric excesses are up to 50%. The pro-(S) hydrogen is removed by amides having (S) configuration. Homochiral diethyl (S)-phenyl[D1]-methyl phosphate [(S)-16c] is deprotonated by both LDA and n-BuLi with a high primary kinetic isotope effect (kH/D ≍ 50) and isomerizes to the corresponding α-hydroxy phosphonate with an enantiomeric excess of up to 85%.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19951280814
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    Tris(1,10-phenanthroline)iron(II) Complexes  -  Broad Variation of the Redox Potential by 4,7-Substitution at the Phenanthroline Ligands[1] (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 845-850 
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    ISSN: 0009-2940
    Keywords: Phenanthroline synthesis ; Tris(phenanthroline)iron(II) complexes ; Redox potential ; Cyclic voltammetry ; Electron transfer, outer-sphere ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The new 4,7-donor-substituted phenanthrolines 2a-h were synthesized and the corresponding tris(1,10-phenanthroline)iron(II) complexes 3a-h studied by cyclic voltammetry. In more detail three novel aza-crown ether-linked (phenanthroline)iron complexes were investigated, the redox potentials of which could be fine-tuned by the addition of group-Ia,IIa metal cations. All iron(II) complexes showed reversible waves at scan rates between 50 and 500 mV · s-1 and could be reversibly oxidized and reduced by chemical means.
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    URL: http://dx.doi.org/10.1002/cber.19951280816
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    Bis(cyclopentadienyl)methane-Bridged Dinuclear Complexes, 10Part 9: B. Stempfle, H. Werner, Gazz. Chim. Ital., 1995, 125, in press. The Bis(cyclopentadienyl)methane Link between Lewis Basic and Lewis Acidic Metal CentersDedicated to Prof. Dr. Herbert Schumann on the occasion of his 60th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 877-881 
    Details
    ISSN: 0009-2940
    Keywords: Bis(cyclopentadienyl)methane ; Heterobimetallic complexes ; Imido complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mononuclear rhodium complexes [(C5H5CH2C5H4)-Rh(CO)2] (1) and [(C5H5CH2C5H4)Rh(PhC≡CPh)(PiPr3)] (2) readily react with nBuLi or TlOEt to yield the corresponding lithium salts 3 and 4 or thallium salts 5 and 6. The reaction of these salts with [(C5H5)Nb(NtBu)Cl2] (7) leads to the formation of the heterodinuclear compounds [{CH2(C5H4)2}-{Rh(CO)2}{(C5H5)Nb(NtBu)Cl}] (8) and [{CH2(C5H4)2}-{Rh(PhC≡CPh)(PiPr3)}{(C5H5)Nb(NtBu)Cl}] (9), respectively. Treatment of 3-6 with [Mo(NtBu)2Cl2] (10) gives the heterodinuclear Rh/Mo complexes [{CH2(C5H4)2}{Rh(CO)2}-{Mo(NtBu)2Cl}] (11) and [{CH2(C5H4)2}{Rh(PhC≡CPh)-(PiPr3)}{Mo(NtBu)2Cl}] (12). The analogous reaction of [Mo(NMes)2Cl2(DME)] (13) with 3-6 yields the corresponding complexes [{CH2(C5H4)2}{Rh(CO)2}{Mo(NMes)2Cl}] (14) and [{CH2(C5H4)2}{Rh(PhC≡CPh)(PiPr3)}{Mo(NMes)2Cl}] (15). From the monometallated ligand [(C5H5CH2C5H4)M] (M = Li: 16; M = Tl: 17) and the imidometal compounds 7, 10 and 13, the mononuclear complexes [(C5H5CH2C5H4)(C5H5)Nb-(NtBu)Cl] (18) and [(C5H5CH2C5H4)Mo(NR)2Cl] (R = tBu: 19; R = Mes: 20) have been obtained.
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    Addition von Hydrofullerid [C60H]- an koordinierte, ungesättigte Kohlenwasserstoffe: Bindung von Fulleren an Metallkomplexe über KohlenwasserstoffbrückenHerrn Professor Herbert Walter Roesky zum 60. Geburtstag gewidmet (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1059-1060 
    Details
    ISSN: 0009-2940
    Keywords: Fullerene ; Hydrofulleride ; Manganese complex ; Rhenium complex ; Iron complexes ; Ruthenium complex ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Addition of Hydrofulleride [C60H]- to Coordinated, Unsaturated Hydrocarbons: Binding of Fullerene to Metal Complexes through Hydrocarbon BridgesHerrn Professor Herbert Walter Roesky zum 60. Geburtstag gewidmet.Hydrofulleride [C60H]- is added to the hydrocarbon ligands of the cationic complexes [(OC)5Re(η2-C2H4)]+, [(OC)3Mn-(η6-C6H6)]+, [(OC)3M(η5-C6H7)]+ (M = Fe, Ru), [(OC)3Fe(η5-C7H9)]+, and [(η5-C5H5)Fe(η6-C5H4CH2)]+.
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    Controlled Conversion of the Transient 2-Mesityl-1,1-bis(trimethylsilyl)silene into a Tetrahydro-2,3-disilanaphthalene, a 1,2-Disilacyclobutane, or a 1,3-Disilacyclobutane (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1083-1088 
    Details
    ISSN: 0009-2940
    Keywords: Silenes ; Silene dimerization ; 1,2-Disilacyclobutanes ; 1,3-Disilacyclobutanes ; 2,3-Disilanaphthalene, tetrahydro- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mesityl[tris(trimethylsilyl)silyl]methanol (1) reacts with strong bases with elimination of trimethylsilanolate according to a Peterson-type mechanism, the outcome of the reaction being dependent on solvent, temperature, and nature of the organometallic base applied. Thus, 1 was converted by treatment with MeLi in ether at -78°C to (E)-1,2,3,8a-tetra -hydro-1-mesityl-5,7,8a-trimethyl-2,2,3,3-tetrakis (trimethylsi-lyl)-2,3-disilanaphthalene (3), formally a [2 + 4] cyclodimer of the transient silene (Me3Si)2Si=CHMes (2). The reaction of 1 with PhMgBr in THF after some days resulted in the formation of (Z)-3,4-dimesityl-1,1,2,2-tetrakis(trimethylsilyl) -1,2-disilacyclobutane (6) as the main product besides small quantities of 3, the polysilane (Me3SiSi(SiMe3)2CH2Mes (10), and the alkoxysilane (Me3Si)3SiCH(Mes)OSi(Si-Me3)2CH2Mes (7). Compound 6, the formal [2 + 2] cycloadduct of 2, can also be obtained by thermal treatment of 3 and is considered to be the thermodynamically more stable silene dimer whereas 3 is the kinetically preferred product. At high LiBr concentrations in the reaction mixture 1 was converted by PhMgBr in THF to (E)-2,4-dimesityl-1,1,3,3-tetrakis(tri- methylsilyl)-1,3-disilacyclobutane (13) besides 6 and [bis(tri-methylsilyl)silyl]mesityl(trimethylsiloxy)methane (11). The unforeseen formation of 13 is discussed as proceeding via the silene-lithium bromide adduct (Me3Si)2Si(Br)CH(Li)Mes (12). In the absence of LiBr 1 was converted by MeLi in THF at -78°C to 11 and the trisilane (Me3Si)2Si(Me)CH2Mes (4b). Probable pathways of the formation of all new compounds are discussed. For 6 and 13 the results of the X-ray structural analyses are given.
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    Metallkomplexe mit biologisch wichtigen Lisganden, LXXXLXXIX. Mitteilung: Lit.. (η3:η3-C10H16)Ru(IV)-Komplexe mit α-Aminocarboxylaten, α-Aminosäureestern und Peptidestern als Liganden (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1117-1125 
    Details
    ISSN: 0009-2940
    Keywords: 1,7-Dimethylocta-2,6-diene-1,8-diyl ; Ruthenium complexes ; α-Amino carboxylates ; α-Amino acid esters ; Peptide esters ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal Complexes Containing Biologically Important Ligands, LXXXLXXIX. Mitteilung: Lit. .  -  (η3:η3-C10H16)Ru(IV) Complexes with α-Amino Carboxylates, α-Amino Acid Esters, and Peptide Esters as LigandsReactions of the chloro-bridged bis(allyl) complex [(η3:η3-C10H16)Ru(Cl)(μ-Cl)]2 with α-amino carboxylates and α-amino acid esters afford the complexes (η3:η3-C10H16)(Cl)RuNH2CHRCO2 (2) and (η3:η3-C10H16)(Cl)2-RuNH2CHRCO2R′ (3). Abstraction of chloride from 3 by Ag+ gives the N,O-chelates [(η3:η3-C10H16)(Cl)RuNH2CHRCO2R′]+BF4 (4). Cysteine methyl ester forms the N,S-chelate complex (η3:η3-C10H16)(Cl)RuNH2CH(CO2CH3)CH2S (5), and with histidine methyl ester a dinuclear complex 6 with N,N-histidine bridge is obtained. Compound 3d with L-PheOEt as ligand was characterized by X-ray diffraction.
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    [MeO(CH2CH2O)3(CH2)3C5Me4]FeCl: A Halfsandwich Iron (II) Chloride Complex of Remarkable Stability (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1135-1136 
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    ISSN: 0009-2940
    Keywords: Hemilabile ligands ; Cyclopentadienyl ligands, functionalised ; Iron compounds ; Halfsandwich complex ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of iron(II) chloride with one equivalent of [MeO-(CH2CH2O)3(CH2)3C5Me4]Li in THF yields the title halfsand-wich complex 1, which is stable in solution up to room temperature. Compound 1 reacts with C5H5Li and CO to give [MeO(CH2CH2O)3(CH2)3C5Me4]Fe(C5H5) (2) and [MeO-(CH2CH2O)3(CH2)3C5Me4]Fe(CO)2CI (3), respectively, in high yields.
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    [Cp4Fe4(E2)2] Clusters with Triangulated Dodecahedral Fe4E4 Skeletons (E = P, As)Dedicated to Professor Herbert Schumann on the occasion of his 60th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1145-1148 
    Details
    ISSN: 0009-2940
    Keywords: P2, As2, P2S2, and P2Se2 ligands ; Iron complexes ; Triangulated dodecahedra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermolysis of [CpFe(CO)2]2 (1) and P4 or As4 affords the iron clusters [Cp4Fe4(E2)2], E = As (2a), P (2b), the Fe4E4 skeleton of which consists of a triangulated dodecahedron. S8 and gray Se oxidize the P2 ligands of 2b with formation of [Cp4Fe4(P2X2)2], X = S (3a), Se (3b), complexes with the hitherto unknown P2X2 ligands, 2a, b and 3a, b have been characterized by X-ray crystallography.
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  • 166
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    Functionalized Diorganozinc Compounds: Key Reagents for the Synthesis of Enantiomerically Pure 2,5-Disubstituted cis- and trans-Tetrahydrofurans (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1021-1028 
    Details
    ISSN: 0009-2940
    Keywords: Synthesis, stereoselective ; Catalysis ; Tetrahydrofurans ; Dialkylzinc reagents ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,4-Diol derivatives 4a-i were synthesized stereoselectively by either reagent- or catalyst-controlled routes using the addition of functionalized diorganozinc reagents to aldehydes. The stereoselectivities along the reagent-controlled synthetic path were in the range between 80:20 and 95:5. The stereoselectivities along the catalyst route exceeded 95:5. The 1,4-diol derivatives 4 thus obtained were transformed into enantiomerically pure cis- and trans-2,5-disubstituted tetrahydrofurans (16-20) by means of an intramolecular Williamson reaction.
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    Contributions to the Chemistry of Boron, 231Part 230: Ref.. Synthesis and Structures of Borylated HydrazinesDedicated to Professor H. P. Fritz on the occasion of his 65th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1187-1194 
    Details
    ISSN: 0009-2940
    Keywords: Hydrazines ; N,N'-bis(diphenylboryl)-N,N'-dimethyl- ; N,N'-bis(diphenylboryl)-N',N'-dimethyl- ; N,N'-bis(dimethylphenylsilyl)- ; N,N'-bis(chloromesitylboryl)-N'-phenyl-N'-(trimethylsilyl)- ; 1,2,4,5,3,6-Tetrazadiborinane, 1,2,4,5-tetrakis(tert-butyldimethylsilyl)-3,6-difluoro- ; Triazadiborolidine, dihydro-, derivative ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The diboration of the diazene PhN = NSiMe3 (15) by diborane(4) derivatives provides a new synthetic route to N,N'-diborylated hydrazines. The product formed depends on the type of the diborane(4) compound. Thus, addition of dimesityldiboron dichloride to 15 in a 1:1 ratio afforded (mesCIB)PhN-N(SiMe3)(BClmes) (16) while bis(dimethyl-amino)diboron dichloride was found to react in a 1:2 ratio to give a triazadiborolidine derivative 17. In addition, it was demonstrated that in the solid state Me2N-N(BPh2)2 (8) is a derivative of a three-membered dihydroazadiboriridine C while its isomer, (Ph2B)MeN-NMe(BPh2) (7), forms no BN coordinative bond. The new 3,6-difluoro-1,2,4,5-tetraza-3,6-diborine 13 shows a twist conformation. The molecular structures of all these compounds were determined by X-ray crystal structure analysis, and the influence of the B substituent on the conformation is discussed.
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    Metal Complexes of Functional Isocyanides, XXV. Amino(hydrazino)carbene Complexes (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1061-1068 
    Details
    ISSN: 0009-2940
    Keywords: N-Isocyanides ; N-Isocyanodialkylamine complexes ; Carbene complexes ; Imaging-Plate data collection ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The N-isocyanodialkylamine metal complexes [M(CO)5CN-NR2] (M = Cr, W), trans-[MI2(CNNR2)2] (M = Pd, Pt), trans-[Pt(Cl)(CNNR2)(PPh3)2]BF4, and cis-[PtCl2(CNNR2)(PPh3)] [R = Et, iPr; 2 R = -{CHMe(CH2)3CHMe}-] react with primary amines to give the amino(hydrazino)carbene metal complexes [M(CO)5(C(NHR′)NHNR2}] (R′ = Me, nPr, Cy) (1-9), trans-[PtI2{C(NHMe)NHNR2}2] (10-12) and trans, and the amine adducts cis-[PtCl2{C(NHMe)NHNC(H)(Me) (CH2)3CHMe}(PPh3)] H2NMe (14), and trans-[PdI2{C (NHMe)NHNC(H)(Me)(CH2)3CHMe}2] 2 H2NMe (15). With secondary amines the amino(hydrazino)carbene metal complexes trans (18) and trans-[PtCl{C(NEt2)NHNEt2} (PPh3)2]BF4 (19) Were isolated. The complexes trans-[PtI2{C(NHCy)NHNiPr2}CNNiPr 2] (20) and trans-[PdI2 (NH2Cy){C(NHCy)NHNiPr2}] (21) were obtained by reaction of trans-[MI2(CNNiPr2)2] (M = Pd, Pt) with cyclohexylamine. The structures were assigned on the basis of IR, NMR- (1H, 13C, 31P), and mass spectroscopy as well as an X-ray structural analysis of 21.
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    Metallocenophanes, VIIPart VI: Ref.. Preparation and Characterisation of the Disilver(I) Complexes of Conjugated Polyenes with [2.2.2]Paracyclophanyl End Groups (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1079-1082 
    Details
    ISSN: 0009-2940
    Keywords: [2.2.2]Paracyclophanes ; Polyenes ; Silver complexes ; X-Ray structural analysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of the disilver(I) complexes 3 and 4, polyene metal complexes that are terminally substituted with [2.2.2]paracyclophanyl units, is described. NMR spectro-scopic studies on the disilver perchlorate complex 3b showed that (a) the sites of complexation are the cyclophane groups and (b) the olefinic spacers do not overly perturb the overall complexation properties of the individual [2.2.2]paracyclo-phanyl groups. The crystal structures of the disilver hexafluo-roantimonate complexes 4a-b were determined. The use of the hexafluoroantimonate counterion and solvent mixtures containing toluene both proved crucial in obtaining single crystals; toluene is incorportated into the crystal lattices.
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    Highly Substituted Tris(pyrazolyl)methane Ligands and Some Zinc Complexes Thereof (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1095-1103 
    Details
    ISSN: 0009-2940
    Keywords: Zinc complexes ; Tridentate ligands ; Tris(pyrazolyl)methane ; Reactivity ; Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tris(pyrazolyl)methane ligands in which two or three of the pyrazole carbon atoms bear organic substituents (L1-L7) were synthesized from chloroform and the corresponding pyrazole under phase transfer conditions. Their behavior towards zinc salts was found to span the range from no reaction at all to hydrolytic destruction. One hydrolysis product isolated and structurally characterized was the perchlorate complex [(HPz5)3Zn-OClO3]ClO4 (1), other ones were the 2:1 complexes (HPz3)2ZnBr2 (2) and (HPz6)2Zn(NO3)2 (3, HPzn = substituted pyrazole). Zinc perchlorate and tris(trimethylpy-razolyl)methane (L2) formed the octahedral binary complex [L22Zn](ClO4)2 (4) as evidenced by a structure determination. Zinc halides produced the 1:1 complexes L1 · ZnBr2 (5), L4 · ZnCl2 (6), and L4 · ZnBr2 (7), which according to the structure determinations of 6 and 7 contain tetrahedral ZnN2Hal2 units with only bidentate tris(pyrazolyl)methane ligands. In contrast, the zinc nitrate complex L4 · Zn(NO3)2 (8) was found to have an octahedral structure with mono- and bidentate nitrate and tridentate L4. The bromide complex 7 was converted by silver perchlorate hydrate into the labile compound [L4 · ZnBr]ClO4 (9) and then into the unstable product [L4 · Zn-OH2](ClO4)2 (10), both presumed to contain zinc in a tetrahedral ZnN3Br or ZnN3O environment, respectively. The ease of hydrolytic self-destruction prevented the exploitation of the reactivity of 9 and 10 in analogy to that of the corresponding tris(pyrazolyl)borate zinc complexes.
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    Unusual Complexation Behavior of Metallomacrocycles Based on Isothiosemicarbazides with Respect to Alkali and Alkaline Earth Metal Ions: Novel 2:1 Associates (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1089-1093 
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    ISSN: 0009-2940
    Keywords: Metallomacrocycles ; Nickel complexes ; Complexation reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions between alkali and alkaline earth metal ions and nickel(II) macrocycles based on S-alkylated isothiosemi-carbazides with different crown ether cavity size were studied in propylene carbonate by spectrophotometric and calorimetric titrations. Metallomacrocycles 1 and 2 exhibit normal behavior on 1:1 complexation with alkali- and alkaline earth metal ions and resemble in this respect 15C5 and 18C6, respectively. The most stable complexes are formed by these “ligands” when the diameter of the cation and the crown ether hole have approximately the same size. The most striking feature of the complexation processes studied is the formation of 1:2 metal-ligand associates even in the case of the smallest cations. These associates are very different from “normal” crown ether sandwich complexes. In reality, the particle formed is an associate between a 1:1 complex, in which the corresponding metal ion is well accommdated inside the ligand cavity, and a second metallomacrocyclic ligand. Their formation is disfavored by enthalpic contributions. A special kind of “switch” from these associates to normal sandwich complexes takes place in the case of 1, when the cation diameter compared to hole size increases. The macrocycle 2 forms this kind of associates with all akali and alkaline earth ions.
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    Synthesis and Reactivity of Silicon Transition Metal Complexes, 3433. Mitteilung: Lit.. Pentachlordisilanyl- und Disilanyl-Komplexe von Molybdän und Wolfram: Darstellung, Struktur und spektroskopische CharakterisierungHerrn Professor Hubert Schmidbaur zum 60. Geburtstag gewidmet. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1109-1115 
    Details
    ISSN: 0009-2940
    Keywords: Silicon transition metal complexes ; Metallodisilanes ; Nucleophilic metallation ; Cl/H exchange at silicon ; Raman spectroscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Reactivity of Silicon Transition Metal Complexes, 34[*].  -  Pentachlorodisilanyl and Disilanyl Complexes of Molybdenum and Tungsten: Synthesis, Structure, and Spectroscopic CharacterizationReaction of the lithium metallates Li[M(PMe3)(CO)2C5R5] [M = Mo, W; R = H (1a, b), Me (1c, d)] with Si2Cl6 (2) leads to the formation of the pentachloro(metallo)disilanes 5R5(OC)2(Me3P)M - SiCl2 - SiCl3 (3a - d), which are transformed into the metallo disilanes C5R5(OC)2(Me3P)M - SiH2 - SiH3 (4a - d) on treatment with LiAlH4. The disilanes 4a - d are reconverted into 3a - d in the presence of tetrachloromethane. Extensive spectroscopic investigations (NMR, Raman, and IR spectroscopy) were performed to establish the transition-metal effect especially with respect to the H5Si2 ligand. The molecular structure of C5Me5(OC)2(Me3P)W - SiCl2 - SiCl3 (3d) was determined by single-crystal X-ray diffraction.
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    Octacarbonylbis {μ-(tris(trimethylsilyl)methyl]indany l} dimanganese with Two Monoalkyl Indium Groups Bridging the Mn-Mn Bond (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1137-1139 
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    ISSN: 0009-2940
    Keywords: Tetraindane(4) ; Indium(I) ; Mn-Mn bond ; Indium alkyl bridge ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrahedra-tetrakis[tris(trimethylsilyl)methyl]tetraindane(4) (1) reacts with decacarbonyldimanganese(0) to yield the bright red crystalline title compound 2, in which two carbonyl ligands are replaced by two InR fragments. The crystal structure determination of 2 shows two Mn(CO)4 groups (Mn-Mn 313.7 pm) bridged by two monoalkylindium units and a planar Mn2In2 molecular center.
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    Thioselonocarboxylic Ester, Selenetane, and Dihydrodiselenine Complexes Prepared from Pentacarbonyl(selenobenzaldehyde)tungsten with π-Donor-Substituted Alkynes (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1149-1156 
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    ISSN: 0009-2940
    Keywords: Selenoaldehyde complex ; Thioselonocarboxylic ester complexes ; Selenetane complex ; Dihydrodiselenine complex ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pentacarbonyltungsten-coordinated selenobenzaldehyde, [(CO)5W{Se=C(Ph)H}] (1), reacts with tBu-C≡C-SMe (2) by insertion of the C≡C into the Se=C bond to form in a highly regio- and stereoselective manner the α,β-unsaturated thioselonocarboxylic ester complex (Z)(C=C)-[(CO)5W{≡1-Se=C(SMe)C(tBu)=C(Ph)H}] (3). The thioselonocarboxylic ester ligand is cleaved intact from the metal by treatment of 3 with [NEt4]Br. Three complexes are formed in the reaction of 1 with Me-C≡C-SMe (5): the thioselonocarboxylic ester complex [(CO)5W{≡1-Se=C(SMe)C(Me)=C(Ph)H}] (6) as a mixture of the (E) and (Z)(C=C) isomers, a selenetane complex (7) and a dihydrodiselenine complex (8). The product distribution depends on the ratio 1:5 and on the solvent. The reaction of 1 with the bis(organylthio)alkynes RS-C≡C-SR (9) [R = Me (a), iPr (b), 2,6-C6H3Me2 (c)] yields mixtures of the (E) and (Z)(C=C) isomers of the α,β-unsaturated α-organylthio thioselonocarboxylic ester complexes [(CO)5W{≡1-Se=C(SR)C(SR)=C(Ph)H)] (10a-c). In contrast, the reaction of 1 with tert-butoxyethyne, H-C≡C-OtBu (11), affords a bis(pentacarbonyltungsten) 5,6-dihydro-1,2-diselenine complex (12). Compound 12 is probably formed by consecutive reaction of 1 with 11 to give the selonocarboxylic ester complex [(CO)5W{≡1-Se=C(OtBu)C(H)=C(Ph)H}] which then further reacts as a heterodiene by highly regioselective [4 + 2] cycloaddition with the Se=C bond of a second molecule of 1 to give 12. In the reaction of 1 with 5 and 9a the isomer with a trans arrangement of C(=Se)SMe and Ph is the kinetically controlled reaction product [(E)-6 and (Z)-10a, respectively]. The formation of (E)-6 and (Z)-10a is followed by isomerization until an (E)/(Z) equilibrium is reached. Complexes 3 and 7 were characterized by X-ray structural analyses.
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    Tin for Organic Synthesis, 13Part 12: Ref.. A New and Regioselective Method for the Synthesis of Aromatic, Heteroaromatic, and Olefinic Sulfonamides by Electrophilic Destannylation (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1195-1198 
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    ISSN: 0009-2940
    Keywords: Electrophilic aromatic substitution ; Electrophilic vinylic substitution ; Trialkylstannanes, application of ; Sulfonamides, synthesis of ; Sulfodestannylation, application of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A mild and effective method for the preparation of aromatic and olefinic sulfonamides is described. The reaction of trialkylaryl- (4a-f), heteroaryl- (4g), and vinylic stannanes (4h) with sulfuryl chloride and secondary amines provides the corresponding sulfonamides in an ipso-specific manner.
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    Ylidylphosphorsulfide, -selenide, -disulfide, -sulfidselenide und -diselenide (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1207-1219 
    Details
    ISSN: 0009-2940
    Keywords: Ylide-substituted phosphorus ; Phosphorus sulfides ; Phosphorus selenides ; Thioxophosphanes ; Selenoxo-phosphanes ; Dithioxophosphoranes ; Diselenoxophosphoranes ; Alkylation reactions ; Selenadiphosphirane ; 2,5,7-Triselena-1,3,4,6-tetraphosphanorbornane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ylidylphosphorus Sulfides, Selenides, Disulfides, Sulfide Selenides, and DiselenidesWe report on the first stable monomeric phosphorus mono-chalcogenides 2, 8 and the first stable dichalcogenides 4, 10 without bulky or intramolecularly coordinating substituents. They are stabilized by a high contribution of the zwitterionic resonance formula, which follows both from the NMR spectra and from an X-ray structure determination. Their preparation starts from triphenylphosphoniumylidyl-dichlorophosphanes 1. For the monochalcogenides they are treated with sodium sulfide or selenide or better with bis(trimethylsilyl) sulfide or selenide. In case of the C-phenyl and C-meta-tolyl representatives and also of the C-trimethylsilyl compound a number of secondary, partly novel products are obtained. - The dichalcogenides result from the reaction with sodium disulfide and diselenide, respectively, or from the oxidation of the monochalcogenides. - Alkylation of the monochalcogenides results in ylidylalkylchalcogenophosphenium salts 13, 15. In solution they are in equilibrium with more or less of the covalent form 14, 16, depending on the anion and on the solvent. Alkylation is often accompanied by secondary reactions. A diselenide loses selenium on alkylation.
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    Synthesis and Reactivity of Silicon Transition Metal Complexes, 3332. Mitteilung: Lit.. Metallo Silanols and Metallo Siloxanes, 87. Mitteilung: Lit.. Metallo-silanole vom Typ C5R5(OC)2(Me3P)M - SiPh2OH (M = Cr, Mo, W): Darstellung nach der Dimethyldioxiran-Methode und Überführung in funktionalisierte Metallo-disiloxaneHerrn Professor Max Schmidt zum 70. Geburtstag gewidmet. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1251-1255 
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    ISSN: 0009-2940
    Keywords: Oxofunctionalization ; Dimethyldioxirane ; Metallo silanes ; Metallo silanols ; Metallo siloxanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Reactivity of Silicon Transition Metal Complexes, 3332. Mitteilung: Lit. .  -  Metallo Silanols and Metallo Siloxanes, 8 7. Mitteilung: Lit. .  -  Metallo Silanols of the Type C5R5(OC)2(Me3P)M-SiPh2OH (M = Cr, Mo, W): Preparation According to the Dimethyldioxirane Route and Conversion into Metallo Disiloxanes Herrn Professor Max Schmidt zum 70. Geburtstag gewidmet.The metallo silanes C5R5(OC)2(Me3P)M-SiPh2H (4a-c), are converted into the corresponding metallo silanols C5R5(OC)2-(Me3P)M-SiPh2OH [R = H, M = Cr (6a); R = Me, M = Mo (6b); M = W (6c)] by oxofunctionalization with dimethyldioxirane (5). Treatment of 6b, c with the chlorosilanes Me2Si(R)Cl [R = H (3b), [R = Cl (3c)] in the presence of triethylamine gives access to the metallo disiloxanes C5Me5(OC)2(Me3P)M-SiPh2OSiMe2R (M = Mo, R = H (7a); M = W, R = Cl (7b)]. The structure of tungsten silanol 6c is determined by X-ray diffraction analysis.
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    Synthesis and Characterization of β-Phosphaenones An Investigation on the Conjugative Properties of the P=C Bond (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 465-476 
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    ISSN: 0009-2940
    Keywords: Phosphaalkenes, C-halo, C-metal ; Phosphaacrylic acid ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermally and air-stable β-phosphaenones were synthesized by functionalization of Mes*P=CCl2 (1; Mes* = supermesityl = 2,4,6-tri-tert-butylphenyl). At low temperature, 1 was lithiated by halogen-metal exchange with n-butyllithium to give the phosphanylidene carbenoid (Z)-Mes*P=C(Cl)Li [(Z)-2] which reacted with acid chlorides to furnish the C-carbonyl-substituted phosphaalkenes (Z)-Mes*P=C(Cl)R (3: P = COtBu; 4: R = COPh; 5: R = COOEt). The reaction of (Z)-2 with carbon dioxide furnished the carboxylate 6, which was converted by treatment with pivaloyl chloride or trimethylsilyl chloride into the phosphaalkenes 7 and 8 functionalized at the carbon atom by an anhydride or a trimethylsilyl ester function, respectively. Acidification of 6 or hydrolysis of 8 with water in chloroform solution afforded the novel carboxylic acid (Z)-Mes*P=C(Cl)COOH (9). Spectroscopic investigations (NMR, UV, IR) of 3-9 and the X-ray structures of 3 and 4 are presented. Based on these properties and on theoretical calculations, the occurrence of conjugation in the β-phosphaenone system is discussed and compared with the well-known conjugation in normal enones.
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    Reactions of Phosphaalkenes with HexafluoroacetoneDedicated to Professor H. M. R. Hoffmann on the occasion of his 60th birthday. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 499-502 
    Details
    ISSN: 0009-2940
    Keywords: Phosphaalkenes ; Cycloadditions ; Insertion reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dimethylamino-substituted phosphaalkene 1 reacts with hexafluoroacetone (HFA) with addition at the P=C bond to form the 1,5,2-dioxaphosphorinane 2. The structure of 2 was confirmed by an X-ray crystal structure analysis. The six-membered ring displays an envelope conformation with the phosphorus atom out of the plane, but the phosphorus is disordered over two sites. Reaction of P-trimethylsilyl-substituted phosphaalkenes with HFA proceeds with retention of the P=C double bond and insertion of HFA into the P—Si bond. Two isomeric products are obtained and are characterized by 1H-, 13C-, 19F-, and 31P-NMR spectroscopy, IR spectroscopy, mass spectrometry, and elemental analysis.
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    Monomere (Acetylacetonato)kupfer(I)-Komplexe von Alkinen und 1,4-Diinen (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 525-529 
    Details
    ISSN: 0009-2940
    Keywords: Copper complexes ; Acetylacetonate ; Alkynes ; 1,4-Diynes ; Titanocenes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monomeric (Acetylacetonato)copper(I) Complexes of Alkynes and 1,4-DiynesMonomeric (η2-Me3SiC≡CSiMe3)Cu(acac) (3) is formed by the reaction of dimeric [(η2-Me3SiC≡CSiMe3)CuBr]2 (1) with two equivalents of Na(acac) (2). In a similar manner Me2-Si(C≡CSiMe3)2 (4) reacts with CuCl (5) and 2 to afford Me2Si[(η2-C≡CSiMe3)Cu(acac)]2 (6). In compounds 3 and 6 an alkyne unit is η2-coordinated to a monomeric Cu(acac) moiety with a copper atom in a planar environment. With the organometallic 1,4-diyne (η5-C5H4SiMe3)2Ti(C≡CSiMe3)2 (7), compound [(η5-C5H4SiMe3)2Ti(C≡CSiMe3)2]Cu(acac) (8) is formed. In 8 both Me3SiC≡C ligands of the 3-titanapenta-1,4-diyne fragment are η2-coordinated to a monomeric Cu-(acac) building block. The copper atom in 8 possesses a pseudo-tetrahedral environment (shown by X-ray analysis), built by the two Me3SiC≡C ligands of the (η5-C5H4SiMe3)2-Ti(C≡CSiMe3)2 moiety and the two oxygen atoms of the acetylacetonato ligand. 8 is additionally formed by the reaction of 3 or 6 with 7, or by treatment of [(η5-C5H4SiMe3)2Ti(C≡C-SiMe3)2]CuCl (9) with Na(acac) (2). The application of 3, 6, and 8 as precursors for the preparation of copper films in the CVD process of copper(I) is discussed.
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    Chiral Organometallic Reagents, XIIIPart XII: Ref.. Structural Aspects of Differentially Solvated Benzyllithium Contact Ion Pairs (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 551-556 
    Details
    ISSN: 0009-2940
    Keywords: Benzyllithium compounds ; Ion pairs ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solvation and ion pair nature of α-(phenylthio)benzyllithium (2d) in THF solution were investigated by NMR-spectroscopic methods. The effect of additives such as diethylene-glycol dimethyl ether or of 12-crown-4 was studied. The results were compared to those of benzyllithium compounds 4 and 6, containing a pentaoxapentadecane ansa chain. These compounds exist as contact ion pairs in which lithium is held at the anionic carbon. This is reflected in the 6Li,13C coupling and 1H,6Li-HOESY contacts in the NMR spectra.
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    Sulfur Compounds, Part 186Part 185: K. Bergemann, M. Kustos, P. Krüger, R. Steudel, Angew. Chem., in print.. The Synthesis of Cyclic Organosulfur Compounds from (C5H5)4Ti2C2S4 by Ligand Transfer Reactions (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 561-564 
    Details
    ISSN: 0009-2940
    Keywords: Titanocene complexes ; Organosulfur ligands ; Ligand transfer ; Organosulfur heterocycles ; Sulfur-sulfur bonds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tetrathiaoxalate complex Cp4Ti2C2S4 (1) reacts with an equimolar amount of COCl2 to give the blue-green mononuclear complex Cp2TiC2S4CO (4). This reaction is analogous to the known reactions of 1 with SCl2 or S2Cl2. However, when 1 was treated with equimolar amounts of the bifunctional sulfenyl chlorides 1,2-C2H4(SCl)2 (5), 1,3-C3H6(SCl)2 (6) or 1,2-C6H4(SCl)2 (7), the bi- or monocyclic tetrakisdisulfanes C6H8S8 (9b), C8H12S8 (10), and C14H8S8 (11), respectively, were obtained. The X-ray crystal structure analysis of 11 · CS2 showed that 11 possesses Ci symmetry with a central exocyclic CC double bond similar to tetrathiafulvalenes: C6H4(μ-S2)2C=C(μ-S2)2C6H4.
    Additional Material: 2 Ill.
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    Norbornadiene(bipyridyl)molybdenum(II) Complexes: Synthesis, Structure and Reactivity of [Mo(CO)(C7H8)(C10H6R2N2)X2] (X = I, Br)Dedicated to Professor Dr. Helmut Werner on the occasion of his birthday. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1007-1013 
    Details
    ISSN: 0009-2940
    Keywords: Tetracarbonyl(norbornadiene)molybdenum(0) ; Oxidative addition of I2 ; Dihalogeno(bipyridyl)molybdenum(II) complexes ; 7-Coordinated complexes ; Neutral and cationic molybdenum(II) complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of [Mo(CO)4(C7H8)] (1) with I2 gave the norbornadienemolybdenum(II) complex [Mo(CO)2(C7H8)I2]n≥1 (2), which existed in an equilibrium of two isomeric forms. In acetonitrile, 2 reversibly formed the adduct [Mo(CO)2-(C7H8)(NCCH3)I2] (3), whereas on treatment with 2,2′-bipyridine or 4,4′-di-2,2′-tBu-bipyridine, it gave stable 7-coordinated molybdenum(II) complexes, [Mo(CO)(C7H8)-(C10H8N2)I2] (4) and [Mo(CO)(C7H8)(C10H6tBu2N2)I2] (5), in good yield. In similar reactions, the related dibromomolybdenum compounds [Mo(CO)(C7H8)(C10H8N2)Br2] (6) and [Mo-(CO)(C7H8)(C10H6tBu2N2)Br2] (7) were prepared by oxidation of 1 with two equivalents of CuBr2. The X-ray structural analysis of 6 reveals that the geometry around the molybdenum atom is nearly perfectly pentagonal bipyramidal, with the CO and one of the bipyridyl rings perpendicular to the plane formed by the other ligands. The compounds 5 and 6 react with AgSbF6 by halogen abstraction to give cationic complexes, {[Mo(CO)(C7H8)(C10H8N2)Br]SbF6}n≥1 (8) and {[Mo(CO)(C7H8)(C10H6tBu2N2)I]SbF6}n≥1 (9): In acetone, 8 and 9 reversibly formed the adducts [Mo(CO)(C7H8)(C10H8N2)(acetone)Br]SbF6 (8′) and [Mo(CO)(C7H8)(C10H6tBu2N2)(acetone)I]SbF6 (9′); while on treatment with PMe3, the stable monomeric complexes, [Mo(CO)(C7H8)(C10H8N2)(PMe3)Br]SbF6 (10) and [Mo(CO)(C7H8)(C10H6tBu2N2)(PMe3)I]SbF6 (11), were isolated in almost quantitative yield. In the presence of KBr, compound 8′ reverted to the dibromo complex 6, whereas 9′ reacted to produce a 1:1:2 mixture of 5, 7 and the bromo(iodo) complex [Mo(CO)(C7H8)(C10H6tBu2N2)BrI] (12). The same mixture is available from the reaction of 5 with one equivalent of 7.
    Additional Material: 1 Ill.
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    Graphical Abstract (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. A149 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951281018
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    Amino Substituted Tricarbonyl(cyclobutadiene)iron Complexes: Pd-Catalyzed Coupling of Iodocyclobutadiene Complexes with Amines (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1055-1058 
    Details
    ISSN: 0009-2940
    Keywords: Aminations ; Palladium catalysis ; Organometallic amines ; Coupling reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coupling of the iodides 1 with amines under palladium catalysis affords the novel aminated cyclobutadiene derivatives 2 in preparative useful yields.
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    Masthead (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951281101
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    Chiral Carbanions, 1. Configurational Stability and Reactions of α-Acyloxy-Substituted α-Methylbenzyllithium Compounds (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1069-1077 
    Details
    ISSN: 0009-2940
    Keywords: Esters, 1-phenylethyl ; Carbanions, α-methyl-α-oxybenzyl, Configurational stability ; Ester - hydroxy ketone rearrangement ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic and optically active 1-phenylethyl esters of pivalic, ( - )-camphanic and 2,4,6-triisopropylbenzoic acid were prepared. The esters 7a of pivalic acid were deprotonated with lithium 2,2,6,6-tetramethylpiperidide (Li-TMP) to form α-oxy-α-methylbenzyllithium compounds which are partly con-figurationally stable prior to acylation with starting material. Camphanic ester (-)-7b cannot be deprotonated by Li-TMP and tBuLi is added to the ester function to afford ketone (-)-12a. 1-Phenylethyl 2,4,6-triisopropylbenzoates 16 were transformed within minutes to carbanions 19 by using sBuLi/TMEDA in THF, hexane, toluene and sBuLi without TMEDA in toluene/20% diethyl ether at -78°C. The carbanions are configurationally stable only in toluene/20% diethyl ether and racemise partly in the other solvents. They react with a variety of electrophiles with either retention [MeOD, AcOD, (MeO)2CO, CICO2Me] or inversion (Me3SnCl) of configuration. Carbanions 19 rearrange on warming to -20°C to hydroxy ketone 24 with racemisation.
    Additional Material: 1 Tab.
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    Metal Complexes with Tetrapyrrole Ligands, LXIX. Facile Synthesis and 13C-NMR Spectrum of Dichloro(octaethylporphyrinato)zirconium(IV) (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1131-1133 
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    ISSN: 0009-2940
    Keywords: Zirconium(IV) octaethylporphyrin complex ; Dichlorozirconium(IV) porphyrin complex ; Precursor of organometallic compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of dichloro(2,3,7,8,12,13,17,18-octaethylpor-phyrinato)zirconium(IV), Zr(oep)Cl2, from zirconium tetrachloride and octaethylporphyrin, H2(oep), is described. The reported synthesis is a new and simple route to this precursor of organometallic compounds. Zr(oep)Cl2 was characterized by elemental analyses, 1H- and 13C-NMR, UV/Vis, and mass spectra. Hydrolysis yielded a mixture of mono- and binuclear hydroxy zirconium(IV) porphyrins.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19951281112
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    Synthesis and First Applications of a New Chiral Auxiliary (tert-butyl 2-(tert-butyl)-5,5-dimethyl-4-oxoimidazolidine-1-carboxylate) (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1185-1206 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Both enantiomers of tert-butyl 2-(tert-butyl)-5,5-dimethyl-4-oxoimidazolidine-1-carboxylate (11; Bbdmoic) were prepared from L-alanine (Schemes 1 and 2). The parent heterocycle, 2-tert-butyl-5,5-dimethylimidazolidin-4-one (12; from 2-aminoisobutyramide, H-Aib-NH2, and pivalaldehyde) was also available in both enantiomeric forms by resolution with O,O′-dibenzoyltartaric acid. The compound (R)- or (S)-11 was used as an auxiliary, but also as a chiral Aib building block in a dipeptide synthesis. The 3-propanoyl derivative 13 of (R)-11 was used for the preparation of enantiomerically pure 2-methyl-3-phenylpropanoic acid (enantiomer ratio (e.r.) 99.5:0.5), by benzylation of the Zn-enolate (→ 14; Scheme 3). Oxidative coupling of the bis-enolate derived from heptanedioic acid and (S)-11 (→ 23) and methanolysis of the auxiliary gave dimethyl trans-cyclopentane-1,2-dicarboxylate (26) with an e.r. of 93:7 (Scheme 5, Fig. 5). The 3-(Boc-Gly)-Bbdmoic derivative 29 was doubly deprotonated and, after addition of ZnBr2 alkylated with alkyl, benzyl, or allyl halides to give the higher amino-acid derivatives with excellent selectivities (e.r. 〉 99.5:0.5, Schemes 6 and 7). Michael additions of cuprates to [(E)-MeCH=CHCO]-Bbdmoic 36 occurred in high yields, but high diastereoselectivities were only observed with aryl cuprates (diastereoisomer ratio (d.r.) 99:1 for R = Ph, Scheme 8). Finally, 3-(Boc-CH2)-Bbdmoic 17 was alkylated through the ester Li-enolate with primary and secondary alkyl, allyl, and benzyl halides with diastereoselectivities (ds) ranging from 91 to 98%, giving acetals of Boc-Aib-Xxx-O(t-Bu) dipeptides (Scheme 4). The effectiveness of Bbdmoic is compared with that of other chiral auxiliaries previously used for the same types of transformations.
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    Synthetic Studies towards Pseurotin A. Part 3.Part 2: [1]. Synthesis of a related highly functionalized γ-lactoneDedicated to Albert Eschenmoser on the occasion of his 70th birthday (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1278-1290 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new general concept for the total synthesis of pseurotin A (1), a secondary metabolite of Pseudeurotium ovalis STOLK, which possesses a highly substituted 1-oxa-7-azaspiro[4.4]nonane skeleton, is presented. A key intermediate of the planned reaction sequence is the functionalized γ-lactone 8. The corresponding protected compound 52 was prepared using (S)-O,O-isopropylideneglyceraldehyde (13) and the bromoacetal 14 as starting material. γ-Lactone 52 was obtained in enantiomerically pure state in ten steps. It possesses the desired configuration.
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    Metal Complexes with Macrocyclic Ligands. Part XL.Part XXXIX: [1]. Syntheses and silver(I) complexes of mono- and disubstituted dithiadiazamacrocycles (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1325-1333 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of N2S2-macrocycles with ring sizes varying between 12 and 16, as well as two 12-membered N2S2-rings with a pendant carboxylic and amino group, respectively, were synthesized. Their complexation properties towards Ag+ were studied by pH titrations and by potentiometry with a silver electrode. The observation that 1:1 ([AgLH2]3+, [AgLH]2+, [AgL]+) and 1:2 species ([AgL2H2]3+, [AgL2H]2+, [AgL2]+) were formed is interpreted by postulating that Ag+ can bind either to the S-donors only, or to both the N- and S-atoms. The most stable complex [AgL]+ in the series of the nonfunctionalized macrocycles was found for the 12-membered N2S2-ring 3. The stability of it increased when an additional donor group was introduced into the side chain. The highest formation constant (logβ110 = 14.43(1)) was obtained with the 12-membered ring 12 carrying the ethanamine side chain. In view of a radiochemical application, all Ag+ complexes were tested in blood serum for their stability, but were not stable enough against transmetallation.
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    Mitteilungen (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1392-1392 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/hlca.19950780525
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    Total Synthesis with a Chirogenic Opening Move Demonstrated on Steroids with Estrane or 18a-Homoestrane SkeletonFrom the Ph.D. theses of M.D.G.[1],A.D.[2],W.D.[3],R.I.S.[4],M.B.[5], and the Diploma thesis of G.T.D.[6].Abbreviations used: BHT: 2,6-di(tert-butyl)-4-methylphenol; HMDS: 1,1,1,3,3,3-hexamethyldisilazane; HMPT: Hexamethylphosphoric triamide.Dedicated to Albert Eschenmoser on the occasion of his 70th birthday (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1345-1391 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A concept of first choice for the synthesis of the title compounds had been proposed by Dane in the late 1930s. It was soon turned down, because the opening move-a chirogenic Diels-Alder reaction - did not work. With Lewis acids as mediators, however, a successful start has been achieved now. With Ti complexes of chelating ligands (Seebach's TADDOLs (= α,α,α′,α′-tetraaryl-1,3-dioxolane-4,5-dimethanols)), enantioselective formation of the desired adducts does occur. Efficient total syntheses of 2 and 3a have been accomplished.
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    Synthesis of an Isotopically Isomeric Mixture of 1,4,6,8-Tetramethyl[13C2]azulene and Its Thermal Reaction with Dimethyl Acetylenedicarboxylate (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1419-1436 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sodium [1,3-13C2]cyclopentadienide in tetrahydrofuran (THF) has been prepared from the corresponding labelled [13C2]cyclopentadiene which was synthesized from 13CO2 and (chloromethyl)trimethylsilane (cf. Scheme 10) according to an established procedure. It could be shown that the acetate pyrolysis of cis-cyclopentane-1,2-diyl diacetate (cis-22) at 550 ± 5° under reduced pressure (60 Torr) gives five times as much cyclopentadiene as trans-22. The reaction of sodium [1,3-13C2]cyclopentadienide with 2,4,6-trimethylpyrylium tetrafluoroborate in THF leads to the formation of the statistically expected 2:2:1 mixture of 4,6,8-trimethyl[1,3a-13C2], -[2,3a-13C2]-, and -[1,3-13C2]azulene (20; cf. Scheme 7 and Fig. 1). Formylation and reduction of the 2:2:1 mixture [13C2]-20 results in the formation of a 1:1:1:1:1 mixture of 1,4,6,8-tetramethyl[1,3-13C2]-, -[1,3a-13C2]-, -[2,3a-13C2]-, -[2,8a-13C2]-, and -[3,8a-13C2]azulene (5; cf. Scheme 8 and Fig. 2). The measured 2J(13C, 13C) values of [13C2]-20 and [13C2]-5 are listed in Tables 1 and 2. Thermal reaction of the 1:1:1:1:1 mixture [13C2]-5 with the four-fold amount of dimethyl acetylenedicarboxylate (ADM) at 200° in tetralin (cf. Scheme 2) gave 5,6,8,10-tetramethyl-[13C2]heptalene-1,2-dicarboxylate ([13C2]-6a; 22%), its double-bond-shifted (DBS) isomer [13C2]-6b (19%), and the corresponding azulene-1,2-dicarboxylate 7 (18%). The isotopically isomeric mixture of [13C2]-6a showed no 1J(13C,13C) at C(5) (cf. Fig. 3). This finding is in agreement with the fact that the expected primary tricyclic intermediate [7,11-13C2]-8 exhibits at 200° in tetralin only cleavage of the C(1)—C(10) bond and formation of a C(7)—C(10) bond (cf. Schemes 6 and 9), but no cleavage of the C(1)—C(11) bond and formation of a C(7)—C(11) bond. The limits of detection of the applied method is ≥96% for the observed process, i.e., [1,3a-13C2]- 5 + ADM→ [7,11-13C2]-8→[1,6-13C2]-9 →[5,10a-13C2]-6a (cf. Scheme 6).
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    On the Funicolides, Briaranes of the Pennatulacean Coral Funiculina quadrangularis from the Tuscan Archipelago: Conformational preferences in this class of diterpenes (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1479-1489 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetic and equilibrium NMR studies of briarane diterpenes isolated from the pennatulacean coral Funiculina quadrangularis showed that funicolide A (1), funicolide D (5), and brianthein W (6), with R2 = Hβ, undergo slow flipping by rotation of the C(1)—C(2)—C(3)—C(4) dihedral angle, giving rise to two observable conformers in a 4:96 population ratio, both having an axial AcO—C(14) and C(16) pointing ‘downwards’, but differing for pseudoaxial or pseudoequatorial position of R1O, respectively. δ(C) for the minor conformers could be quickly assigned by an original emulation methodology. Similar studies revealed that funicolide B (2), 7-epifunicolide A (4), funicolide E (7), and unnatural epibrianthein W (8) undergo similar motions, where, however, the nature of the α-positioned substituent R2 determines which conformer predominates: axial R1O for R2 = Hβ (4 and 8) or equatorial R1O for R2 α-OH, (2 and 7). In contrast, funicolide C (3) proved to undergo slow conformational motions that involve also the cyclohexene ring, resulting in two observable conformers characterized by either an equatorial AcO—C(14) and trans-diaxial C(2)/C(9) or an axial AcO—C(14) and trans-diequatorial C(2)/C(9) in a 9:1 population ratio, respectively. These observations, and molecular-mechanics calculations for briaranes known to exhibit broad NMR signals, lead to general views on the conformational preferences of diterpenes of this class.
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    1,3-Dipole mit zentralem S-Atom aus der Umsetzung von Aziden mit Thiocarbonyl-Verbindungen: Eine unerwartete MeS-Wanderung im Abfangprodukt eines ‘Thiocarbonyl-aminids’ mit Dithiobenzoesäure-methylesterTeilweise von G.M. an der Jahresversammlung der Polnischen Chemischen Gesellschaft in Warschau, September 1994, vorgetragen.Herrn Professor Dr. Klaus Hartke in Würdigung seiner Beiträge zur Schwefelorganischen Chemie gewidmet (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1499-1510 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,3-Dipoles with a Central S-Atom from the Reaction of Azides and Thiocarbonyl Compounds: An Unexpected MeS Migration in the Trapping Product of a ‘Thiocarbonyl-aminide’ with Methyl DithiobenzoateReaction of PhN3 with O-methyl thiobenzoate (11a) and thioacetate (11c) as well as with the dithio esters 11b,d at 80° yields the corresponding imidates and thioimidates 12 (Scheme 3). The formation of 12 is rationalized by a 1,3-dipolar cycloaddition of the azide and the C=S group followed by successive elimination of N2 and S. In the three-component reaction of 11b, PhN3, and the sterically crowded thioketone 1a, 1,2,4-trithiolane 13a and 1,4,2-dithiazolidine 3a are formed in addition to 12b (Scheme 4). The heterocycles 13a and 3a are trapping products of 1a and ‘thiocarbonyl-thiolate’ 5a and ‘thiocarbonyl-aminide’ 2a (Ar=Ph), respectively (Scheme 6). These 1,3-dipoles are formed as reactive intermediates. Surprisingly, in the presence of catalytic amounts of acids, the major product is the (methyldithio)cyclobutyl thioimidate of type 14 (Scheme 5), formed by an acid-catalyzed MeS migration in dithiazolidine 17. A reaction mechanism is proposed in Scheme 7.
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    Synthesis of a Type-VIβ-Turn Peptide Mimetic and Its Incorporation into a High-Affinity Somatostatin Receptor Ligand (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1588-1606 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of a cis-Phe-Pro dipeptide mimetic is described, which adopts a type-VIβ-turn conformation. In this mimetic, the α-positions of Phe and Pro are joined by a CH2CH2 bridge, thereby forming a fused bicyclic system, and fixing a geometry similar to that seen in cis-Phe-Pro units in protein crystal structures. The dipeptide mimetic 20 was synthesized in optically pure form starting from (R)-α-allylproline (6; Schemes 1, 3, and 4), with a free carboxylic acid and an Fmoc-protected N-terminus, thereby allowing its incorporation into linear and cyclic peptides using standard solid-phase methods. The mimetic 20 was incorporated into the cyclic somatostatin analogue cyclo(-Phe = Pro-Phe-D-Trp-Lys-Thr-), where Phe = Pro represents the mimetic. This analogue shows a high affinity (pIC50 8.6) for somatostatin receptors on rat-brain cortex membranes. Based on NMR studies in aqueous solution, likely low-energy conformations for this analogue were deduced using restrained dynamic simulated annealing. The conformations found, which include a distorted type-II′ turn at D-Trp-Lys, are similar to low-energy conformations deduced elsewhere for cyclo(-Phe-Pro-Phe-D-Trp-Lys-Thr-), as well as to those seen in crystal structures of the somatostatin analogue octreotide.
    Additional Material: 7 Ill.
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    Mitteilungen (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1620-1620 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780616
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    Synthesis and Reductive Complexation Properties of a Cone-Configurated Tetra[p-(tert-butyl)]calix[4]arene incorporating bipyridyl and pyridine subunits. NMR characterization and crystal structure of its chiral copper(I) complex (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1607-1619 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hetero-armed p(tert-butyl)calix[4]arene 1 was synthesized by a stepwise procedure. This ligand presented a very strong complexing behavior towards Cu1, giving the chiral complex 2 and parent species when reacted with CuII salts. High-resolution NMR techniques were employed for the characterization of 2, demonstrating notably exchange processes between its two enantiomeric forms. The racemic nature of 2 was confirmed by X-ray crystal-structure analysis.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19950780615
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    Molecular Magnetism and Iron(II) Spin-State Equilibrium as Structural Probes in Heterodinuclear d-f Complexes (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1651-1672 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fe(ClO4)2 reacts with the segmental ligand 2-{6-[1-(3,5-dimethoxybenzyl)-1H-benzimidazol-2-yl]pyridin-2-yl}-1,1′-dimethyl-5,5′-methylene-2′-(5-methylpyridin-2-yl)bis[1H-benzimidazole] (L2) in MeCN to give the diamagnetic deep violet complex [Fe(L2)2]2+ where the metal is pseudo-octahedrally coordinated by two perpendicular tridentate binding units. When L2 reacts with an equimolar mixture of Ln(ClO4)3 (Ln = La, Ce, Pr, Nd, Sm, Eu) and Fe(ClO4)2, electrospray-mass spectrometric, spectrophotometric, and 1H-NMR data in MeCN show the selective formation of the deep red heterodinuclear C3-cylindrical complexes [LnFe(L2)3]5+ where the three ligands L2 are wrapped about the metal-metal axis. FeII occupies the pseudo-octahedral capping site produced by the three bidentate units and LnIII lies in the resulting ‘facial’ pseudo-tricapped trigonal prismatic site defined by the three remaining tridentate coordinating units. The heterodinuclear complexes [LnFe(L2)3]5+ display spin-state equilibrium (1A ⇄ 5T) and thermochromism in MeCN between 243 and 333 K. Detailed 1H-NMR, UV/VIS, and magnetic measurements in solution show that the partial spin-crossover behavior of [LnFe(L2)3]5+ occurs for Ln = La—Eu with similar thermodynamic parameters (ΔHsc = 20-23 kJ·mol-1 and ΔSsc = 55-66 J·mol-1·K-1) indicating that the size of LnIII has a negligible influence on the spin-state equilibrium. However, the smaller LnIII ions have less affinity for the pseudo-tricapped trigonal prismatic coordination site in the heterodinuclear complexes as demonstrated by the partial decomplexation of [YFe(L2)3]5+ to give [Fe(L2)2]2+ and the absence of the heterodinuclear complex [LuFe(L2)3]5+ under the same conditions. The crucial role played by the sterically demanding FeII in the assembly processes is discussed together with the use of the efficient combination of lanthanide probes with magnetic d-block probes for the design and investigation of luminescent and magnetic materials with controlled structural and physical properties. Photophysical measurements reveal that efficient ligand → metal and Eu → Fe energy transfer occur in [EuFe(L2)3]5+ which strongly quench both the ligand and the Eu-centered luminescence.
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    URL: http://dx.doi.org/10.1002/hlca.19950780704
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