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  • Organic Chemistry  (822)
  • Inorganic Chemistry  (773)
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  • 1990-1994  (1,596)
  • 1991  (1,596)
  • 101
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: To find out whether the 1,4-addition to 1,2:3,4-diepoxides, which so far has been observed only once, is of a more general character, we investigated the reaction of a variety of O-, C-, N-, and S-nucleophiles with the model compound 1,2:3,4-diepoxy-2,3-dimethylbutane (Scheme 4). In several cases, 1,4-addition products could, indeed, be observed besides the expected 1,2-adducts (Table).
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  • 102
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Crystal Structure of the First Quinoid Dihydropterinmolybdenum (IV) ComplexThe first molybdenum(IV) complex with a quinoid dihydropterin, i.e. 2, was isolated and characterized by IR, UV and NMR data and single-crystal X-ray diffraction. The reaction of MoVIO2Cl2 with the biologically important 6β-5,6,7,8-tetrahydro-L-biopterin(2) (7) in MeOH gave almost quantitatively trichloro(1,5-quinoid-7,8-dihydro-6H-L-biopterin)oxomolybdenLim(IV) (2). The complex crystallizes with one molecule of MeOH in the noncentrosymmetric orthorhombic space group P212121 (No. 19) with unit cell dimensions a = 1009.3(3), b = 1104.7(3), and c = 1484.5(4) pm and Z = 4. The Mo-atom has a distorted octahedral geometry (Fig.1). It is coordinated by N(5) and O(4) of the pterin ligand. The distance of the Mo-N(5) bond (202 pm) is unusually short compared to similar complexes. O(4) is located trans to a terminal oxo ligand. The octahedral coordination is completed by three Cl-atoms in a meridional arrangement. Complex 2, with the Mo-atom in the enzyme-relevant oxidation state +IV and the pterin in the intermediate quinoid dihydro form, should lead to an extension of the proposed ‘common molybdenum cofactor’ model.
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  • 103
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: UV irradiation of the unsaturated (E)-5,10-secosteroidal ketones 1 and 6 results, in addition to (E/Z)-isomeri-zation, in an intramolecular Pateino-Büchi reaction and, in the case of 1, in transannular cyclization (along with AcOH elimination). The stereochemistry of the observed intramolecular photoprocesses can be explained in terms of ground-state conformations of the (E)-seco-ketones 1 and 6 in solution.
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  • 104
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 1489-1499 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ‘Push-Poll’ Effect of ‘Push-Pull’ Oligoacetylenes. A 13C-NMR InvestigationAccording to 13C-chemicaI shifts of ‘push-pull’ oligoacetylenes 1-4, the ‘push-pull’ effect (i.e. π delocalization induced by ‘push-pull’ substituents) rapidly decays in this series. To correct for other than π -charge-density effects, Δδ values of symmetrically placed C-atoms of the oligoacetylene chain are discussed. Stereoelectronic resteffects (SER) of the substituents on terminal C-atoms of PP-ketones 1a-3a and PP-esters 1b-4b are estimated from the residual Δδ of the asymptotes of Fig. 3. Fig. 4 convincingly shows that Δδ values are dramatically decreasing with increasing number n of acetylene units between the push and pull substituents. Assignment problems of ‘push-pull’ triacetylenes 3 have been solved by 13C labelling of the CO group of 3a.
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  • 105
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 1520-1532 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: C-Glycosides of N-Acetylneuraminic AcidThe synthesis of the C-glycosides 8, 15, and 9 of N-acetylneuraminic acid is described. Hydroxymethylation of the Li-ester enolate, derived from 5, yielded the protected C-glycosides 7 and 10 (46%; 3:1), which were deprotected to yield 8 (54%) and 15 (51%; Scheme 2). The mesylate 16 was obtained from 7 (73%) and transformed via the azide 17 (75%) into the acid 18 (66%) and the amino acid 9 (Scheme 3). The configuration at C(2) of 17 was proved by transforming 17 into the bicyclic lactam 19. Both 8 and 15 are very weak inhibitors of Vibrio cholerae sialidase; 9 appears to stimulate this enzyme.
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  • 106
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 1585-1590 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Based upon our novel concept for the total synthesis of cytochalasans, the model lactams 2-9 were treated with Bu2Cu(CN)Li2. The results of these conversions vary much from those obtained with Ph2Cu(CN)Li2, demonstrating the uncertainty of predictions in cuprate chemistry. The bicyclic compound 20 was prepared in good yield. However, all attempts to convert p-toluenesulfonate 20 into the Ph-substituted derivative 21, an intermediate for the synthesis of cyiochulusm B(1), have failed so far.
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  • 107
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    Helvetica Chimica Acta 74 (1991), S. 1608-1609 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 108
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    Helvetica Chimica Acta 74 (1991) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 109
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new approach to ketose-derived nucteosides is described. It is based upon a chain elongation of 1-deoxy-1-nitroaldoses, followed by activation of the nitro group as a leaving group, and introduction of a pyrimidine or purine base. Thus, the nitroaldose 7 was prepared from 3 by pivaloylation (→4), synthesis of the anomeric nitrones 5/6, and ozonolysis of 6 (Scheme 1). Partial hydrolysis of 4 yielded 8/9, which were characterized as the acetates 10/11 and transformed into the nitrones 12/13. Ozonolysis of 12/13 gave 14/15, which were acetylated to 16/17. Henry reaction of 7 lead to 19 and 20, which were acetylated to 21 and 22 (Scheme 2). Michael addition of 7 to acrylonitrile and to methyl propynoate yielded the anomers 23/24 and 25/26, respectively. Similar reactions of 16/17 were prevented by a facile β-elimination. Therefore, the nitrodiol 15 was transformed into the orthoesters 27 and then, by Henry reaction, partial hydrolysis, and acetylation, into 28 and 29 (Scheme 2). The structure of 19 was established by X-ray analysis. It was the major product of the kinetically controlled Henry reaction of 7. Similarly, the β-D-configurated nitroaldoses 23 and 25 were the major products of the Michael addition. This indicates a preferred ‘endo’-attack on the nitronate anion derived from 7. AMI calculations for this anion indicate a strong pyramidalization at C(1), in agreement with an ‘endo’-attack. Nucleosidation of 21 by 31 afforded 32 and 33. Yields depended strongly upon the nature and the amount of the promoter and reached 77% for 33, which was transformed into 34, 35, and the known ‘psicouridine’ (36; Scheme 3). To probe the mechanism, the trityl-protected 30 was nucleosidated yielding 37, or 37 and 38, depending upon the amount of FeCl3. Nucleosidation of the nitroacetate 28 was more difficult, required SnCl2 as a promoter, and yielded 39 and 40. The β-D-anomer 40 was transformed into 36. Nucleosidation of 23 (SnCl4) yielded the anomers 41 and 42, which were transformed into 43 and 44, and hence into 45 and 46 (Scheme 4). Similarly, nucleosidation of 25 yielded 47 and 48, which were deprotected to 49 and 50, respectively. The nucleoside 49 was saponified to 51. Nucleosidation of 21 by 52 (SnCl2) afforded the adenine nucleosides 53 and 54 (Scheme 5). The adenine nucleoside 53 was deprotected (→55→56) to ‘psicofuranine’ (1), which was also obtained from 58, formed along with 57 by nucleosidation of 28. The structure and particularly the conformation of the nitroaldoses, nitroketoses, and nucleosides are examined.
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  • 110
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiraspher, a polymer of ethyl N-acryloylphenylalanine on spherical silica gel, is used for the preparative separation by recycling chromatography of the enantiomers of oxazolidinones rac-5, thioxolanone rac-6, per-hydropyrimidinone rac-7, and dioxinones rac-9 and 10 derived from the acids listed in the title (Figs. 1-5). The oxazolidinones rac-1a, -2, and -4 show a peculiar peak of the separation efficiences upon lowering the Chiraspher-column temperature to 15° (Fig. 6). In some cases, multigram amounts of enantiomerically pure heterocycles could thus be prepared. The absolute configurations of most enantiomers are assigned. First applications of the tert-butyl 5-oxo-2-phenyloxazolidine-3-carboxylate (5) as a nucleophilic chiral glycine building block are described (products 13-16, Scheme 2). A list of enantiomerically pure 1,3-dioxinones is presented (Table 1), showing a correlation between their absolute configuration, sense of optical rotation, and elution behavior on Chiraspher.
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  • 111
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    Helvetica Chimica Acta 74 (1991), S. 1697-1706 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of phospholipids 1n-3n, rationally designed for two-dimensional crystallization of progesterone and estradiol receptors, is reported. The structure of these lipids provides them with essential properties such as fluidity and stability when spread into monolayers at the air/H2O interface, affinity for the protein to be crystallized, and accessibility of the ligand under the lipid monolayer.
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  • 112
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solution studies of the Cu2+ complex with 11-(3-aminopropyl)-1,4,7,11-tetraazacyclotetradecane(L) indicate that, depending on the pH and on the age of the solution, different species are present. Dissolving the solid [CuL](ClO4)2 in slightly acidic solution gives the protonated complex AH, characterized by an absorption maximum at 574 nm, by a relatively fast proton-induced dissociation kinetics and by the typical colour change in basic solution to give the deprolonated form A with coordinated side chain. AH slowly interconverts in acidic solution to a new species BH, which has an absorption maximum at 547 nm, and which is kineticaily more stable against acid dissociation and shows no coordination of the amino group of the side chain. In alkaline solution, however, the deprotonated form B deliver A in a base induced reaction. The X-ray diffraction studies of A and BH allow to determine the geometry of the metal ion and the configuration of the macrocycle. In A, the Cu2+ is pentacoordinated by the five N-atoms of the ligand and the macrocycle is in the RRSR configuration, whereas in BH the Cu2+ is octahedrally coordinated by the four N-atoms of the macrocycle and two axial perchlorate O-atoms with the macrocycle in the RRRS configuration. The amino group of the side chain is protonated and not coordinated. Thus, the on/off equilibrium of the side chain not only changes the geometry of the metal ion, as is generally found, but also alters the macrocyclic moiety.
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  • 113
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [(l-6):(1′-6′)-η-Pentaphenyltriphosphane(5)]chromium (8), which is formed from bis(lithio-η6-benzene)-chromium and dichlorophenylphosphane, and which is prepared more rationally from bis(chloro-η6-benzene)-chromium and K2P3Ph3, is the first sandwich complex featuring an interannular oligophosphane bridge -(PPh)n-, n ≥ 2; 31P{1H}- and 1H-NMR spectra suggest that the stereoisomer 8-meso1 is formed exclusively and that the -(PPh)3- link in this triphospha[3]chromocyclophane is non-fluxional in the range 193 〈 T 〈 348 K.
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  • 114
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    Helvetica Chimica Acta 74 (1991), S. 2068-2072 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The neutral molecules nitrosoformaldehyde (1a), 1-nitrosoacetaldehyde (1b), and 2,2,2-trifluoro-1-nitrosoacetaldehyde (1c) have been generated and detected by neutralization-reionization mass spectrometry (NR-MS).
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  • 115
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    Helvetica Chimica Acta 74 (1991), S. 2054-2067 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 9-(2′-deoxy-à-D-threo-pentofuranosyl)adenine (=9-(2′-deoxy-à-D-xylofuranosyl)adeninc, xAd; 2) was protected at its 6-NH2 group with cither a benzoyl (5a) or a (dimethyfamino)methylidcnc (6a) residue and with a dimethoxytntyl group at 5′-OH (5b, 6b). Compounds 5b and 6b were then converted into the 3′-phosphonates 5c and 6c; moreover, the 2-cyanoethyl phosphoramidite 6d was synthesized starting from fib. The DNA building blocks were used for solid-phase synthesis of d[(xA)122-A] (8). The latter was hybridized with d[(xT)12-T] (Tm = 35°); in contrast, with d(T12), complex formation was not observed. Moreover, xAd and xTd were introduced into the self-complementary dodccamcr d(G-T-A-G-A-A-T-T-C-T-A-C) (12) at different positions lo give the oligomcrs 13-16. All oligonucleotides were characterised by temperature-dependent CD and UV spectroscopy, and in addition, 14 by T-jump experiments. From concentration-dependent Tm measurements, the thermodynamic paraneters of the melting as well as the tendency of hairpin formation of the oligonucleotides were deduced. Oligemer 14 was hydrolyzed by snake-venom phosphodiesterase in a discontinuous way implying a fast hydrolysis of unmodified 3′- and 5′-flanks followed by a slow hydrolysis of the remaining modified tetramer. In contrast to this, oligonucleotide 16 was hydrolyzed in a continuous reaction. In both cases, calf-spleen phosphodiesterase hydrolyzed the oligomer only marginally.
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  • 116
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    Helvetica Chimica Acta 74 (1991), S. 1936-1940 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal isomerizations of N-[α-(alkylthio)alkyl]- and N-[α-(arylthio)alkyl]benzotriazoles have been investigated under N2 atmospheres (i) in toluene, xylene, MeOH, or EtOH, in the presence of acid catalysts and (ii) in the absence of solvent. The sulfide isomerization rates depend on the number of H-atoms carried by the C-atom attached to the N-atom of the benzotriazole: tertiary (no hydrogen) 〉 secondary (1 hydrogen) 〉 primary (2 hydrogens). The results support an isomenzation mechanism involving a heterolytic N—C bond cleavage with formation of sulfonium/carbonium and benzotriazolate ions.
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  • 117
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of cyclosporin A (CsA) with Lawesson's reagent under different conditions yields various thiocyclosporins, in which carbonyl O-atoms and/or the hydroxy O-atom of the MeBmt residue are replaced by an S-atom. The position of the S-atom is determined by NMR spectroscopy, and the conformations of the products are studied by NMR spectroscopy and X-ray crystallography. Some of the thiocyclosporins show interesting conformational properties. Whereas one conformation strongly dominates for CsA in CDCL3, two conformers A and B, in a ratio 58:42 are found for [1ψ2, CS-NH]CsA. Extensive NMR studies including new 2D and 3D heteronuclear techniques and restrained MD calculations using ROE effects demonstrate that the major conformer A is identical to CsA, while the minor conformer B contains an additional cis peptide bond between the Sar3 and MeLeu4 residues. [4ψ5, CS—NH; 7ψ8, CS-NH]CsA exhibits a conformation very similar to crystalline CsA. However, the D-Ala8NH, MeLeu6Co γ-turn H-bond is not present in this dithio analogue. Also different is the MeBmt1side-chain conformation, the dithio conformation showing a strong MeBmt1OH, Sar3CO H-bond. Immunosuppressive activities of thiocyclosporins are measured in IL-2 and IL-8 reporter gene assays. Their activities are discussed in relation to their conformations.
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  • 118
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diazo transfer from trifluoromethanesulfonyl azide (TfN3) to 2-amino-2-deoxy-glycoses constitutes a high-yielding, simple procedure for the preparation of partially protected or unprotected 2-azido-2-deoxy-aldoses. Thus, the D-allosamine derivative 2 gave 93% of 3, while diazo transfer to D-glucosamine, D-mannosamine, and D-galactosamine, followed by acetylation, yielded the azides 5, 7, and 9 in yields of 74-91, 65, and 70%, respectively.
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  • 119
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    Helvetica Chimica Acta 74 (1991), S. 2078-2093 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical anions often monocyclic and bicyclic azoalkanes containing the azo group in (Z)-conformation, have been fully characterized by their hyperfine data with the use of ESR, ENDOR, and general-TRIPLE-resonance spectroscopy. These azoalkanes are represented by 3,3,5,5-tetramethyl-1-pyrazoline (1), 2,3-diaza-bicyclo[2.2.1]hept-2-ene (4), and 2,3-diazabicyclo[2.2.2]oct-2-ene (9), as well as by their derivatives 2,3, 5-8, and 10. For all radical anions 1″-10″, the 14N-coupling constant, aN, is in the range of +0. 83 to +0. 97 mT; this finding indicates that the spin population is essentially restricted to the π system of the azo group. The 14N-hyperfine anisotropy largely affects the width of ESR lines, particularly at low temperatures. Substantial coupling constants of 7Li-, 23Na-, 39K-, and 133Cs-nuclei point to a close association of the radical anions with their alkali-metal counterions. With the exception of 39K, these nuclei give rise to readily observable ENDOR signals which appear along with those stemming from protons. The prominent hyperfine features of 1″-10″ are discussed.
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  • 120
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The benzyl- and the acyl-protected glyconolactone tosylhydrazones 6, 9, 12, 16, and 19 (Scheme 1) were prepared in good yields by treating the hemiacetals 4, 7, 10, 14, and 17 with N-tosylhydrazine, to give the N-glycosylhydrazines 5, 8,11,15, and 18, and by oxidizing these hydraz tries with N-bromosuccinimide (NBS) in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), with CrO3-dipyridine complex or with pyridinium dichromate. Photolysis of the sodium sail 20 of 6 (Scheme 2) in the presence of N-phenylmaleimide, dimethyl fumarate, or acrylonitrile gave the corresponding cyctopropanes 21-28 in satisfactory yields. Phololytic or thermolytic glycosidation of phenol and 4-melhoxyphenol by 20 yielded the anomeric glycosides 29/30 and 31/32, yields being marginally higher for the Ihermolytic process. Phololytic glycosidation of propan-2-ol gave the glycosides 33 and 34 in low yields only. Yields and ratios of products were compared to those obtained with the diazirine 1 as a source of glycosylidene carbenes. While the yields from 20 are lower, the ratios of products obtained in the photolytic reactions are in agreement with the formation of a common intermediate from both carbene precursors.
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  • 121
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    Helvetica Chimica Acta 74 (1991) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 122
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Naturally occurring (-)-(R,R)-α-necrodol ((-)-1) and its C(4)-epimer (-)-2 are obtained in 84 and 44% yields, respectively, by lithium ethylenediamide (LEDA) treatment of the corresponding β-necrodols (-)-3 and (-)-4 (Scheme 1, Table), both readily available from (-)-campholenyl acetate ((-)-i) by an efficient stereoselective synthesis. The thermodynamically preferred (-)-(R)-γ-necrodol ((-)-5) becomes the major product (≥ 80% yield) after either prolonged treatment with LEDA or exposure of α- and β-necrodols to BF3·Et2O. In an alternative route, (+)-5 is prepared starting from (+)-campholenal ((+)-ii) via Pd-catalysed decarbonylation to (-)-(S)-1,4,5,5-tetramethylcyclopent-l-ene ((-)-6) and subsequent application of an acid-catalysed CH2O-addition/rearrangement sequence (Scheme 2).
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  • 123
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sodium and europium cryptates of the new macrobicyclic ligands 2 and 3 incorporating the 2,2′-bipyri dine 1,1′-dioxide and 3,3′-biisoquinoline 2,2′-dioxide units, respectively, have been prepared. The EuIII complexes present characteristic 1H-NMR spectra, showing large shifts, and are strongly luminescent in aqueous solution. These markedly improved luminescent properties, compared to the europium cryptate of the parent macrobicyclic ligand 1, may be ascribed at least in part to a better shielding of the bound cation by the N-oxide sites.
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  • 124
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    Helvetica Chimica Acta 74 (1991), S. 611-616 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Investigation of the tubers of Eranthis hyemalis (Ranunculaceae) afforded six chromenone glycosides. Their structures have been elucidated mainly by spectroscopic (FAB-MS, 2D-NMR techniques) and chemical methods (acidic and enzymatic hydrolysis) as 9-{[(β-D-glucopyranosyl)oxy]methyl}-8,11-dihydro-5-hydroxy-2-methyl-4H-pyrano[2,3-g][1]benzoxepin-4-one (1), 9-{[(β-D-gentiobiosyl)oxy]methyl}-8,11-dihydro-5-hydroxy-2-methyl-4H-pyrano[2,3-g][1]benzoxepin-4-one(2), 9-{[(β-D-glucopyranosvl)oxy]melhyl}-8,11-dihydro-5-hydroxy-2-(hydroxy-methyl)-4H-pyrano[2,3-g][1]benzoxepin-4-one(3), 8-{(2E)-4-[(β-D-glucopyranosyl)oxy]-3-methylbut-2-enyl}-5,7-dihydroxy-2-methyl-4H-1-benzopyran-4-one (4), 8-{(2E)-4-[(β-D-glucopyranosyi)oxy]-3-methylbut-2-enyl}-5,7-dihydroxy-2-(hydroxymethyl)-4H-1-benzopyran-4-one (5), and 7-{[(β-D-glucopyranosy1)oxy]methyl}-2,3-dihydro-2-(l-hydroxy-1-methylethyl)-4-methoxy-5H-furo[3,2-g][1]benzopyran-5-one (6). Compound 2 exhibited negative inotropic activity.
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  • 125
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of N1,4-Di(p-coiimaroyl)spermine, a Possible Biogenetic Precursor of AphelandrineCoupling of two differently substituted 1,3-diaminopropane units 5 and 6 (Schemes 1 and 2) lead to the key intermediate 8, a tetra-N-protected spermine derivative. By selective deprotection and alkylation with (E)-4-(mesyloxy)cinnamoyl chloride, followed by deprotection, 8 was transformed to the target spermine derivative 19. By an alternative route, the 1,3-diaminopiopanes 10 and 11 were combined to the tri-N-protected tetraamine 12. The intermediates 8 and 12 can be used for the preparation of polyamine derivatives.
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  • 126
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    Helvetica Chimica Acta 74 (1991), S. 671-681 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The four photo-cleavable ligands 1-4 of the macrobicyclic-cryptand type have been synthesized by introducing a photo-sensitive 2-nitrobenzyl- or 4,5-dimethoxy-2-nitrobenzyl-ether bond into one of the bridges. These compounds are expected to retain the selective binding features of the parent cryptands and to allow the photolytically induced release of alkali ions in aqueous solution. The crystal structures of the ligand 5-(2-nitro-phenyl)-4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (3) and of its KSCN complex 13 have been determined. They are analogous to those of the corresponding parent species, confirming the macrobicyclic geometry and the cryptate nature of the complex. Spectroscopic properties are reported.
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  • 127
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,3-Dihydro-1H-benz[f]indole-4,9-diones are formed in one-step in 45-82% yields by an unprecedented [2+3]-type regioselective photoaddition of 2-amino-1,4-naphthoquinone with various electron-rich alkenes and the [2+3] adducts derived from ammonaphthoquinone with vinyl ethers and vinyl acetate to give 1H-benz[f]indole-4,9-diones including a benzindole-dione with a kinamycin skeleton in 33-72% yields. A probable pathway leading to the formation of the dihydroindole-dione involving air oxidation of an intermediary hydroquinone is proposed.
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  • 128
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    Helvetica Chimica Acta 74 (1991), S. 1135-1142 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Irradiation of dicarbonyl(η5-cyclopentadienyl)iron dimer 1 or decacarbonyldimanganese (2) in the presence of alkyl halides leads to C-centered radicals which can be trappedby alkenes and yields saturated and/or unsaturated addition products. Carbon radicals are generated via halogen abstraction by the initially formed metal-centered radicals resulting from homolysis of the metal-metal bond of dimeric mediators 1 and 2. No reaction occurs using octacarbonyldicobalt (3).
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  • 129
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    Helvetica Chimica Acta 74 (1991), S. 189-196 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbonyl(cycloheptatrienyl)iodo(phosphorus donor)tungstens ([WI(C7H7)(CO)L]; L = P(OMe)3, 1a; L = P[O(i-Pr)]3, 1b; L = PPh3, 1c) were prepared from dicarbonyl(cycloheptatrienyl)iodotungsten ([WI(C7H7)(CO)2)] via a carbonyl-substitution process. Similarly, bromocarbonyl(phosphorus donor)(1,2,4,6-tetramethylcycloheptatrienyl)tungstens ([WBr(Me4C7H3)(CO)L]; L = P(OMe)3, 6a; L = P[O(i-Pr)]3, 6b; L = PPh3, 6c) were obtained from the reaction of bromodicarbonyl(1,2,4,6)-tetramethylcycloheptatrienyl)tungsten ([WBr(Me4C7H3)(CO)2]; 4) with L. The reduction of 1a-c, 4, and 6a, b with sodiumdihydridobis(2-methoxyethoxy)aluminium in toluene led to stable hydrido complexes [WH(R4C7H3)(CO)L] (R = H, L = P(OMe)3, 2a; R = H, L = P[O(i-Pr)]3, 2b; R = H, L = PPh3, 2c; R = Me, L = P(OMe)3, 7a; R = Me, L = P[O(i-Pr)]3, 7b; R = Me, L = CO, 7d). Complexes 2a and 7b were characterized by X-ray structure analyses.
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  • 130
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    Helvetica Chimica Acta 74 (1991), S. 241-244 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 131
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    Helvetica Chimica Acta 74 (1991), S. 275-289 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The imine obtained by condensing indole-protected 2-(indol-3-yl)acetaldehyde (5) with the terpinylamine derivative (±)-4 was cyclized in 51% yield to the 19-substituted hobartine derivative (±)-20 upon exposure to anhydrous HCOOH. This pivotal intermediate was further elaborated into the indole alkaloids (±)-serratenone ((±)-22) and (±)-sorelline ((±)-29). In the course of these investigations, a novel rearrangement was uncovered; a Lewis acid-catalyzed 1,3-migration of an arylsulfonyl group from the indole N-atom into the benzene ring. The discovery that synthetic (±)-aristotelin-19-one ((±)-34) has decidedly different spectroscopic properties than aristolasicone, a metabolite for which the structure has been recently proposed, led to a revision of the structure of the latter.
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  • 132
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    Helvetica Chimica Acta 74 (1991), S. 304-308 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homolytic dediazoniation of tribromo- and trichloro-benzenediazonium tetrafluoroborates in highly ionizing, low-nucleophilicity solvents (trifluoroethanol and trifluoromethanesulfonic acid (TfOH)) exhibits a strong magnetic-field dependency of dediazoniation products; a more facile singlet-to-triplet intersystem crossing results in increased radical-escape products at higher magnetic fields.
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  • 133
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    Helvetica Chimica Acta 74 (1991), S. 469-486 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Enantiomerically Pure Mimulaxanthin and of Its (9Z,9′Z)- and (15Z)IsomersWe present the details of a synthesis of optically active, enantiomerically pure stereoisomers of mimulaxanthin (=(3s,5R,6R,3′S,5′R,6′R)-6,7,6′,7′-tetradehydro-5,6,5′,6′-tetrahydro-β,β-carotin-3,5,3′,5′-tetrol) either as free alcohols 1a and 24a or as their crystalline (t-Bu)Me2Si ethers 1b and 24b. Grasshopper ketone 2a, a presumed synthon, unexpectedly showed a very sluggish reaction with Wittig-Horner reagents. Upon heating with the ylide of ester phosphonates, an addition across the allenic bond occurred. On the contrary, a slow but normal 1,2-addition took place with the ylide from (cyanomethyl)phosphonate but, unexpectedly, with concomitant inversion at the chiral axis. So a mixture of(6R,6S,9E,9Z)-isomers 6-9 was produced {(Scheme 1). However, a fast and very clean 1,2-addition occurred with the ethynyl ketone 12 to yield the esters 13 and 14 (Scheme 2). DIBAH reduction of the separated stereoisomers gave the allenic alcohols 15 and 16 in high yield. Mild oxidation to the aldehydes 17 and 18 followed by their condensation with the acetylenic C10-bis-ylide 19 led to the stereoisomeric 15,15′-didehydromimulaxanthins 20 and 22, respectively (Schemes 3 and 4). Mimulaxanthins 1 and 24 were prepared by partial hydrogenation of 20 and 22 followed by a thermal (Z/E)-isomerization. As expected, the mimulaxanthins exhibit very weak CD curves, obviously caused by the allenic bond that insulates the chiral centers in the end group from the chromophor. On the contrary, some of the C15-allenic synthons showed not only fairly strong CD effects but also a split CD curve which, in our interpretation, results from an exciton coupling between the allene and the C(9)=C(10) bond. We postulate a rotation around the C(8)—C(9) bond, presumably caused by an intramolecular H-bond in 16 or by a dipol interaction between the polarized double bonds in 6, 7, 8, and 17.
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  • 134
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    Topics: Chemistry and Pharmacology
    Notes: The new axially dissymmetric diphosphines (R)- and (S)-(6,6′-dimethoxybiphenyl-2,2′-diyl)bis(diphenyl phosphine) ((R)- and (S)-5a; ‘MeO-BIPHEP’) and the analogues (R)- and (S)-5b and 5c have been synthesized in enantiomerically pure form. These ligands have become readily available by a synthetic scheme which employs, as key steps, an ortho-lithiation/iodination reaction of the (m-methoxyphenyl)diprienylphosphine oxides 8 and a subsequent Ullmann reaction of the resulting iodides 9 to provide the racemic bis(phosphine oxides) 10. The bis(phosphine oxides) 10 subsequently are resolved with (-)-(2R,3R)- and (+)-(2S,3S)-O-2,3-dibenzoyltartaric acid and reduced to diphosphines 5. The Ullmann reaction constitutes a new and efficient route to 2,2′-bis(phosphinoyl)-substituted biphenyl systems. Absolute configurations were established for (R)-5a by X-ray analysis of the derived Pd complex (R,R)-17a, and for 5b and 5c by means of 1H-NMR comparisons of the derived Pd complexes 16 or 17, respectively, and by means of CD comparisons. The MeO-BIPHEP diphosphine 5a proved to be as efficient as the previously described BIPHEMP diphosphine ((6,6′-dimethylbiphenyl-2,2′-diyl)bis(diphenylphosphine)) in enantioselective isomerizations and hydrogenations.
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  • 135
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    Helvetica Chimica Acta 74 (1991), S. 430-437 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of 3-[2-(morpholin-4-yl)vinyl]-1H-indole (1), the 1,2-dihydro-9H-carbazole 2, as well as the 3-(tetrahydropyridin-4-yl)-1H-indoles 3a and 3b with some carbo- and heterodienophiles are described. The scope and limitations of the synthetic utility of these amino- (or homoamino)-functionalized 3-vinyl-1H-indoles are reported and some MO calculations for the qualitative prediction of their reactivities are presented. The reactions gave rise to substitution products, redox products, Diels-Alder adducts, ene adducts, and Michael-type adducts (Schemes 2 and 3).
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  • 136
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    Helvetica Chimica Acta 74 (1991), S. 465-466 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 137
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    Topics: Chemistry and Pharmacology
    Notes: From the gun resin Ammoniacum, an epimeric mixture 2a/3a of highly functionalized prenylated chromandiones was isolated. Their structure was established by spectral data and single-crystal X-ray analysis. The compounds were isolated as acetates 2b/3b, and these derivatives showed in vivo haemorrhagic activity.
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  • 138
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    Topics: Chemistry and Pharmacology
    Notes: The sponge Stelletta sp. (Astrophorida, Stellettidae), collected at -700 m in the Coral Sea, is shown to contain sterones and sterols of the stigmastane type with a C(24)=C(25) bond for which there is no precedent in the sea. Structure elucidation of the second abundant of these steroids, stigmasta-4,24(25)-dien-3-one ((+)-1), is based on 1D and 2D NMR spectra and chemical transformation to acetate (-)-5. Stigmasta-4,24(25)-diene-3,6-dione ((-)-3), present in trace amounts in the sponge, was obtained in sufficient quantity for NMR study by oxidation of the also present, inseparable, and abundant 4:1 mixture of stigmasta-5,24(25)-dien-3β-ol (6) and its 5,6-dihydro derivative 7 (Scheme 1). This oxidation also afforded the ketone analogues (+)-8 and (+)-9, which could be separated, thus making structure elucidation possible. The 6β-hydroxystigmasta-4,24(25)-dien-3-one ((+)-4), also present in trace amounts in the sponge, was obtained in sufficient amount for NMR study, together with its C(6) epimer (+)-11, by hydroperoxidation of (+)-8 followed by deoxygenation (Scheme 2). The last trace steroid of the sponge, stigmasta-4,6,24(25)-trien-3-one ((-)-2), was structurally elucidated using limited NMR data and comparison with the other stigmastanes. These stigmastanes, as the only steroids of this sponge, are likely to function as stabilizers of its cell walls; their phytosteroid structure, for a sponge which lives in the dark of deep waters, suggest origin through a complex food chain, possibly followed by bioelaboration in the sponge.
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  • 139
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    Topics: Chemistry and Pharmacology
    Notes: A new approach to the total, asymmetric synthesis of D-threo-L-talo-octose ((-)-1) and its derivatives is presented. It is based on the chemoselective Wittig-Horner monoolefination of a 5-deoxy-D-ribo-hexodialdose derivative 4 obtained by selective reduction of (-)-5-deoxy-2.3-O-isopropylidene-/β-D-ribo-hexofuranurono-6,1-lactone ((-)-3). Allylic bromination of the resulting methyl (E)-oct-6-enofuranuronate (+)-5 followed by intramolecular nucleophilic displacement of the so-obtained bromides gave a 13.3:1 mixture of (-)-methyl (E)-l,4-anhydro-6,7-dideoxy-2,3-O-isopropylidene-β-L-talo-oct-6-enopyranuronate ((-)-8) and methyl (E)-l,4-anhydro-6,7-dideoxy-2,3-O-isopropylidene-α-D-allo-oct-6-enopyranuronate (9). The double hydroxylation of the enoate (-)-8 followed Kishi's rule and gave the corresponding D-threo-β-L-talo-octopyranuronate derivative (-)-11 with a good diastereoselectivity. Reduction of ester (-)-11 and deprotection led to pure (-)-1.
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  • 140
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    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 4-chloropyrroIo[2,3-d]pyrimidine and 2-amino-4-chloropyrrolo[2,3-d]pyrimidine α-D- and β-D-2′,3′-dideoxyribonucleosides 6a, b and 7a, b is described (Scheme 1). Glycosylation of the pyrrolo[2,3-d]-pyrimidinyl anions of 1a, b with in situ prepared 2,3-dideoxy-α/β-D-glycero-pentofuranosyl chloride (2) was regioselective but afforded anomeric mixtures of the 2′,3′-dideoxyribonucleosides 3a/4a and 3b/4b, respectively. The glycosylation products were deprotected and subjected to nucleophilic displacement yielding various pyrrolo[2,3-d]pyrimidine 2′,3′-deoxyribonucleosides related to 2′,3′-dideoxyadenosine and 2′,3′-dideoxyguanosine. One-pot phosphorylation gave the corresponding triphosphates. Some of them are strong inhibitors of HIV-1 reverse transcriptase, similar to corresponding purine 2′,3′-dideoxynucleotides, but exhibit a better selectivity index in comparison to DNA polymerases. According to that, the N(7) of the purine moiety is not an essential binding position of ddATP or ddGTP at the active centre of HIV-1 reverse transcriptase.
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  • 141
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    Helvetica Chimica Acta 74 (1991) 
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 142
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of a derivative of coenzyme F430 from methanogenic bacteria, the bromide salt of 12,13-diepi-F430 pentamethyl ester (5, X = Br), was determined by X-ray structure analysis. It reveals a more pronounced saddle-shaped out-of-plane deformation of the macrocycle than any hydroporphinoid Ni complex investigated so far. The crystal structure confirms the constitution proposed for coenzyme F430 (2) and shows that in the epimer 5, the three stereogenic centers in ring D, C(17), C(18), and C(19), have the (17S)-, (18S)-, and (19R)-configuration, respectively. Deuteration and 2D-NMR studies independently demonstrate that native coenzyme F430 (2) has the same configuration in ring D as the epimer 5. Therefore, our original tentative assignment of configuration at C(19) and C(18) [1] has to be reversed. This completes the assignment of configuration for all stereogenic centers in coenzyme F430, which has the structure shown in Formula 2.
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  • 143
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    Topics: Chemistry and Pharmacology
    Notes: Column chromatography of easy available (±)-physovenine (2) on cellulose triacetate afforded (-)- and (+)-physovenine (2a and 2b, resp.). Alkaloids 2a, b required for pharmacological testing were prepared from eserolincs (3a, b) by an improved procedure. Natural (-)-physovenine (2a) was equally potent in inhibiting AChE and BChE in vitro as natural physostigmine (1a), and twice as potent as the unnatural antipode 2b against AChE and 14 times as potent against BChE. Several carbamate analogs of 2a were at least as potent as the former compound in these assays. None of the compounds tested did bind to different opiate receptor or serotonine receptor preparations. Most of the compounds tested had considerable analgesic activity in the Writhing test.
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  • 144
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    Topics: Chemistry and Pharmacology
    Notes: The absolute configurations of acetylated bretonin A (= (+}-(R)-1-[(acetoxy)methyl]-2-{[(4E,6E,8E)-dodeca-4,6,8-trienyl]oxy}ethyl 4-acetoxybenzoate; (-)-1b) and isobretonin A (= (+)-(S)-3-{[(4E,6E,8E)-do-deca-4,6,8-trienyl]oxy}-2-hydroxypropyl 4-hydroxybenzoate; (+)-2), previously isolated from an undetermined sponge of the North Brittany sea, were established by comparison with synthetic (+)-lb and (+)-2, obtained from the condensation of commerical (-)-(R)-2,2-dimethyl-1,3-dioxolan-4-yl p-toluenesuifonate ((-)-(R)-15) with a mixture of (4E,6E,8E)- (14e) and (4E,6Z,8E)-dodeca-4,6,8-trien-1-ol (14z). This also allowed confirming the structure and configuration of bretonin B (= (S)-2-{[(4E,6Z,8E)-dodeca-4,6,8-trienyl]oxy}-1-(hydroxy-methyl)ethyl 4-hydroxybenzoate; 3) which was also isolated from the same sponge, albeit in a too small amount for a complete study. As concerns the glyceryl ethers precursors of the bretonins, co-occurrence of the usual (S)-con-figuration (from 1a) with the unusual (R)-configuration (from (+)-2)) poses intriguing biogenetic problems.
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  • 145
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cluster compounds [Pt3(μ-CO)3(PR3)3] act as Lewis bases towards the metal halides of Group XI, MX, Group XII, MX2, and Group XIII, MX3, to form cluster compounds of the composition [{MXn}{Pt3(μ-CO)3(PR3)3}]. The X-ray crystal structure, NMR and IR data are given for the compound [{ZnI}{Pt3(μ-CO)3(PPh(i-Pr)2)3}].
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  • 146
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    Topics: Chemistry and Pharmacology
    Notes: The products formed on UV irradiation of several tricyclic compounds (i.e. 3, 6, 8, 15, and 17, Schemes 2-4) were studied in detail. A marked dependence of the reaction course on the type and site of substitution was found. Among the several light-induced transformations, a novel rearrangement, i.e. 11 to 9 (Scheme 3) was identified. The formation of the polycyclic compound 13 on irradiation of 8a (Scheme 3) resulted from an unexpected skeletal rearrangement with dearomatization of one benzene ring. The structures of compounds 10, 11, and 13 were established by X-ray crystallography (Figs. 1-3). An attempt was made to give a general mechanistic picture of all observed photochemical results (Schemes 4-6).
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  • 147
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    Topics: Chemistry and Pharmacology
    Notes: N-Nitroacetyl derivatives of L-proline, L-valine, and L-phenylalanine esters were prepared in two steps under mild conditions (Scheme 2). Regiospecific mono- and bis-allylation of these nitroacetyl derivatives were accomplished in presence of a Pd(0) catalyst. The bis-allyl derivatives 7-9 were obtained in 40-75% yield. The tertiary NO2 group in these compounds could be transformed into an acetylamino group by Zn/AcOH/Ac2O. The final products 11-13 are dipeptides in which the N-terminal glycine residue bears two α-allyl substituents.
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  • 148
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    Helvetica Chimica Acta 74 (1991), S. 1119-1126 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By aromatic nucleophilic substitution followed by intramolecular acylation, 9-oxo-9H-thioxanthene- and 9-oxo-9H-xanthene-dicarboximides were prepared from nitro- or chlorophthalimides and the dianions of thiosalicylic and salicylic acids (Scheme). The 9-oxo-9H-thioxanthene-3,4-dicarboximides were converted to 9-oxo-9H-thioxanthene-3,4-dicarboxylic-acid derivatives such as anhydride, esters, and further imides. Some of these derivatives proved to be excellent photosensitizers with special properties such as liquid aggregation form, H2O solubility, solubility in lipophilic organic solvents and polymers, or bathochromic shifts of the absorption wavelengths.
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  • 149
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    Helvetica Chimica Acta 74 (1991) 
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    Topics: Chemistry and Pharmacology
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  • 150
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structures of the LiBr complexes of two macrobicyclic ligands, [py.py.bpy]1 and [py.biqi.biqi] 2, have been determined. They confirm the cryptate nature of these species. In 3, the Li+ cation is bound in the shallow cavity of a ligand of flattened shape, whereas in 4, it is buried inside the macrobicycle and surrounded by its three bridges.
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  • 151
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    Helvetica Chimica Acta 74 (1991), S. 1213-1220 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of methyl 2-(1-hydroxyalkyl)prop-2-enoates 1 with conc. HBr solution afforded methyl (Z)-2-(bromomethyl)alk-2-enoates 2, which were transformed regioselectively into N-substituted methyl (E)-2- (aminomethyl)alk-2-enoates 3 (SN2 reaction) and into N-substituted methyl 2-(1-aminoalkyl)prop-2-enoates 4(SN2′ reaction). Regiocontrol of nucleophilic attack by amine was accomplished simply by choice of solvent, the SN2 reaction occurring in MeCN and the SN2′ reaction in petroleum ether. Hydrolysis and lactamization afforded β-lactams 7 and 8, containing an exocyciic alkylidene and methylidene group at C(3), respectively.
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  • 152
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The original suggestion that a through-space mechanism was operative in the seven-bond J(P, P) coupling constant of 30.3 Hz observed for 3.3′-bis(1,1-dimethylethyl)-2,2′-[3,3′,5,5′-tetrakis(1,1-dimethylethyl)-1,1′-biphenyl-2,2′-diyl]bis(oxy)}bis[1,3,2-oxazaphospholidine] (1a)) was investigated. In the solid-state CP-MAS 31PNMR spectrum of 1a, two nonequivalent P-atoms were observed; sufficient resolution could not be obtained to determine whether P, P coupling was present. The preparation and spectral data of the N-methyl analogue 1b and of the acyclic N-isopropyl analogue 6 (Scheme 1) provided evidence that a) the essentially exclusive formation (R*, R*,S*)-1ain the reaction of the disodium biphenyldiolate 3a with the phosphorochloridite 4a is the result of significant differences in the free energy of activation (ΔG*) for the formation of the various diastereoisomers due to the steric congestion within the molecule and that b) the magnitude of the observed P,P coupling is dependent upon the degree of conformational freedom within the molecule. In the 31P-NMR spectrum of the P-sulfide 7, which was prepared by the reaction of la with sulfur, 2s resonances were observed that strongly suggested that the lone electrons pair on P are involved in the mechanism for the transmission of coupling data. The (4S,5R)-12 and (4R, 5S)-12 of la were prepared in a three-step reaction sequence starting from the corresponding enantiomerically pure norephredine 8 (Scheme 2). Both (4S, 5R)- and (4R, 5S)-12 were obtained as a diastereoisomer mixture that differ by the configuration of the axis of chirality, i.e., (R*R*,R*)- and (R*,S*,R*)-12 were obtained. The major diastereoisomer was obtained upon recrystallization, and the atropisomers were observed to equilibrate in solution by monitoring the H—C(5) resonance in the 1H-NMR with time (ΔG° = 0.4 kcal/mol; Fig. 2). The process observed corresponds to the restricted rotation about the central single bond of the biphenyl system. The isolation of an atropisomer with only a single ortho substituent on each aryl ring is quite rare. In the 13C-NMR spectrum of both (R*,R*,R*)- and (R*,S*,R*)-12, C(5) is two-bond-coupled to the oxazaphospholidine P-atom (2J(C(5),P((2)) = 8.5 Hz) that is further virtually coupled to the P-atom of the other oxazaphospholidine ring (7J(P(2),P(2′)) = 30 Hz; 9J(C(5),P(2′)) = 0 Hz; δ(P(2)) = δ(P(2′)) = 136 ppm. In the 31P-NMR spectrum of (R*,R*,S*)-12, which was prepared from the racemic chloridite (mixture of three diastereoisomers was obtained), a 7J(P(2),P(2′) of 36 Hz was observed. These observations provide strong evidence that seven-bond P,P coupling occurs in all three diastereoisomers of 12. The observed P,P coupling is both independent of the configuration of the chiral axis and the configuration of the asymmetric P-centers. This independence of P,P coupling upon the configuration on P implies also the independence of the observed coupling upon the orientation of the lone-pair of electrons on P provided that the conformations of the diastereoisomers are similar in solution. The X-ray crystal structure of the complex formed from 1a and dichloro(cycloocta-1,5-diene)platinum(II) was obtained and the solid-state structure discussed. The major diastereoisomer of (4S,5R)-12 was used as a chiral ligand in asymmetric hydrosilylation and hydrogenation reactions (Scheme 3).
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  • 153
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The major alkaloid from Rauwolfia serpentina cell-suspension cultures, the glucoalkaloid raucaffricine (2), was enzymatically formed from vomilenine (1) and UDPG in presence of microsomal-bound enzyme. This glucosyltransferase exhibits a relatively high substrate specificity with strong preference for 1 and UDPG. The apparent Km values for 1 and UDPG were 40 μM and 0.8 mM, respectively, for raucaffricine formation. Optimum transferase activity was observed at 50° and pH 6.3. The taxonomic distribution of this enzyme seems to be very limited because transferase can he exclusively detected in raucaffricine-producing plant cells.
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  • 154
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    Helvetica Chimica Acta 74 (1991), S. 1742-1748 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 2′-deoxyisoguanosine (2), and the pyrrolo[2,3-d]pyrimidine and pyrazolo[3,4-d]pyrimidine 2′-deoxyribonucleosides 3 and 4 is described. Condensation of the imidazole precursor 5 with benzoyl isocyanate followed by reaction with ammonia gave 2. Its N(7) regioisomer was obtained from 6. Compound 2 was also prepared by the photochemically induced conversion of 2-Chloro- and 2-bromopurine 2′-deoxyribofuranosides 9a and 10, respectively, in aqueous solution, The photo reaction was further used for the synthesis of the compounds 3 and 4 starting with the amino-chloro-2′-deoxynucleosides 9b and 9c, respectively.
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  • 155
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optical Isomers of Naftidrofuryl( = 2-(Diethylamino)ethyl 2-[(Naphth-1-yl)methyl]-3-(tetrahydrofur-2-yl)propanoate)The four optical isomers of naftidrofuryl (1) were prepared in two ways, by separation and resolution of the two diastereoisomeric racemates and by synthesis from the enantiomers of tetrahydrofuran-2-methanol (6); see Scheme}. The absolute configuration of one of the isomer as a tartrate monohydrate was established by X-ray crystallography thus allowing the deduction of the absolute configurations of the other three optical isomers.
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  • 156
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    Helvetica Chimica Acta 74 (1991), S. 1773-1789 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In higher plants, the two homotcrpenes 4,8-dimethylnona-l,3,7-triene (1) and 4,8,12-trimethyltrideca-1,3,7,11-teiracnc (2) originate from nerolidol (3) or geranyllinalool (4) by anoxidative cleavage of their C-skele-lons. The reaction proceeds with exclusive loss of H8-C(5) of 3 and formal production of a C4 fragment. The site specificity of the enzyme(s) is identical for all of the hitherto examined plant families (Agavaceae, Asclepiadaceae, Asteraceae, Leguminosae, Magnoliaceae, and Saxifragaceae). The enzyme tolerates a wide range of structural modifications at the polar head of 3. Instead of 3, also gcranylacclone 12 and the secondary alcohol 13 can be cleaved to the homoterpene 1 and as yet unidentified carbonyl fragments. The C=C bonds within the aliphatic chain of 3 seem to be essential for the oxidative bond cleavage as well as for recognition and embedding of the substrate into the active center of the enzyme(s). The feed-induced biosynthesis of 1 and 2 in leaves of the Lima bean Phaseolus lunatm infested with the spider mite Tetranychus urticae probably requires a preceding release of nerolidol (3) or geranyllinalool (4) from phylogenic glycosides prior to the fragmentation reaction. The microbial reduction of the trienoic acids 6 and 6ais the key stop for the synthesis of deuterium labelled nerolidol (3RS,5R)-and (3RS,5S)-9.
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  • 157
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    Helvetica Chimica Acta 74 (1991), S. 1931-1935 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: tert-Alkyl sulfides, with an α-(1H-benzotriazol-1-yl) group 6 and 13, are readily prepared from N-[(aryl-thio)methyl]-1H-benzotriazoles 3 and N-(11), respectively, by reaction with BuLi and then with the appropriate electrophile. The tert-alkyl sulfides 6 and 13 are smoothly converted by BF3. OEt2 into vinyl sulfides 5, 7 or 12, respectively, in satisfactory yields.
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  • 158
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of the Macrolide Antibiotic (-)-A2677IB Using Photolactonization as a Key Reaction and Computer Simulation as an Effective Aid in OptimizationThe title compound has been synthesized in a sequence of 21 steps starting from phenol. The cyclic skeleton has been built up in the earlier part of the synthesis by photolactonization. This reaction supplies C(6), with a functionality, not present in the target structure, but useful for oxygenation at C(4) and generation of the stereogenic center C(5). The Barton/McCombie reaction provides a product deoxygenated at C(6), but only after an adjacent oxirane ring has been opened at the cost of an increase in the number of overall steps. X-Ray structural information and computational modelling of appropriate molecules proved to be essential to selection of optimal conditions for various transformations.
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  • 159
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We incorporated 6,7-dimethyllumazine chromophores and a [RuII(bathophenanthroline)] complex into different oligodeoxynucleotides, the former via the corresponding phosphoramidites of the 2′-deoxynucleosides and the latter specifically by the phosphonate approach at the 5′-end of synthetic oligonucleotides, directly in the course of their synthesis on solid support. Efficiency measurements of this energy-transfer system with the lumazine as energy donor and the Ru complex as energy acceptor allowed us to distinguish between the hybridized and the non-hybridized state of oligonucleotides. Thus, the approach should be of value in DNA probe technology for the detection of single-stranded DNA targets.
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  • 160
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The antibiotic myxovirescine M2 was synthesized from seven building blocks (1-7, Scheme 1), with the following chiral starting materials being employed: (S)-malic acid, (+)-D-ribonolactone, (S)-2-(hydroxymethyl)butanoate, and (2R,4S)-5-hydroxy-2,4-dimethylpenLanoate. Three new nucleophilic reagents, 8-10, for C-C bond formation have been used. The key steps of the synthesis are: a Suzuki coupling between an alkyl borane and a vinyl bromide (4 + 12e → 13), a Julia olefinalion (14 + 17 → 18), and a Yamaguchi macrolactonizalion to form the 28-membered lactone (18 → 19), This extremely convergenl synthetic approach will allow the preparation of a number of the 31 known myxovirescine molecules.
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  • 161
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The (-)-(2S)-Diethyl 2-Hydroxyhexanedioate, a New Chiral Building Block for Enantioselective Synthesis(-)-(2S)-Diethyl 2-hydroxyhexanedioate ((2S)-3) has been obtained by enantioselective reduction of diethyl 2-oxohexanedioate (1) with baker's yeast. The key intermediate (-)-(5S)-ethyl 5,6-dihydroxyhexanoate ((5S)-5) is proved to be a useful synthon for the synthesis of chiral δ-lactones and a precursor of leukotriene LTB4 ((5S)-13).
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  • 162
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    Helvetica Chimica Acta 74 (1991), S. 179-188 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure and synthesis of novel irregular C12 terpenoids isolated from quince fruit (Cydonia oblonga MILL.) are described: quince oxepine (= (E)-2,3,6,7-tetrahydro-4-methyl-2-(3-methylbuta-1,3 dienyl)oxepine; 3) and the quince oxepanes as a 1:1 mixture of cis- and trans-isomers (= cis- and trans-(E)-4-methyl-2-(3-methylbuta-1,3-dienyl)oxepane; 4 and 5, resp.). The absolute configurations of the natural compounds have not been determined due to the minute amounts available, but both relative and absolute configurations of synthetic 4 and 5 were established by chemial correlation with (R)-pulegone.
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  • 163
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    Helvetica Chimica Acta 74 (1991), S. 255-274 
    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 a series of 8-R1-substituted as well as of 8,8-R1, R2-disubstituted heptafulvenes, varying from inversely polarized (3l) to unpolar (3h) and polar heptafulvenes with electron-withdrawing groups (3d, e, f), have been analyzed and compared with those of methoxytropylium salt 5a. The results concerning 3J (H,H) values and 13C-chemical shifts are shown in Figs. 5 and 6. It turns out that all the NMR parameters are strongly influenced by substituents R1, R2, but contrary to planar pentafulvenes, no linear correlations of the NMR parameter vs. Hammett substituent constant σ+ are obtained in the series 3l → 3d. 3J coupling constants J(2,3)/J(4,5) and J(3,4) are not much influenced by substituent changes in the series 3l → 3h, but are approaching in the row 3h → 3d. Similarly, signals of the 13C-atoms undergo a moderate shift to higher frequencies in the row 3l → 3h, but are strongly influenced by —M groups, whereby the sensitivity is decreasing in the series C(7) 〉 C(2)/C(5) 〉 C(3)/C(4) 〉 C(1)/C(6). These results are essentially explained by a boat conformation of inversely polarized heptafulvenes of the type 3l and an increasing planarization of the ring on going to polar heptafulvenes of type 3d.
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  • 164
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several synthetic pathways to the anticonvulsivum gabapentin (1-(aminomethyl)cyclohexaneacetic acid) have been investigated. Advantages and drawbacks of the different routes are discussed, and the most economical and technically most feasible synthesis is pointed out.
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  • 165
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    Helvetica Chimica Acta 74 (1991), S. 397-406 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A route for synthesizing C-nucleosides with 2,6-substituted pyridines as heterocyclic aglycones is described. Condensation of appropriately substituted lithiated pyridines with ribono-1,4-lactone derivatives yields hemiacetal 4a-g (Table 1), which can be reduced by Et3SiH and BF3·Et2O to the corresponding C-nucleoside (see Scheme 1 for 4d → β-D-5). Conditions are presented that optimize the amount of the 2,6-dichloropyridine-derived β-D-anomer β-D-5 formed (Table 3). Aminolysis of β-D-5 yields the diaminonucleoside 14 (Scheme 3).
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  • 166
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    Helvetica Chimica Acta 74 (1991), S. 417-429 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Information on the hitherto unknown relative configuration and on the conformation of the title compounds in solution can be derived from nuclear Overhauser effects and coupling constants. Whereas the bridged 5-(dimethoxyphosphoryl)-2-methoxy-1,2λ5-oxaphospholan-2-ones 6 and 7 are sterically strained and, therefore, conformationally rigid, the C(3)-unsubstituted compound 1 does not show a preferred solution conformation. Phenyl substituents at C(3) (compounds 2-5) tend to adopt a pseudoequatorial position, this way leading to a definite conformation of the respective compounds. The influence of the conformation on the NMR spectra is discussed. 31P-NMR Spectroscopy is ideally suited for the characterization and quantification of the isomers 2-5 present in the reaction mixture.
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  • 167
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    Helvetica Chimica Acta 74 (1991), S. 464-464 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 168
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bicyclic alcohol (±)-2, an advanced intermediate for the synthesis of the methyl ester 1 of pentalenolactone E, has been synthesized in nine operations starting from aldehyde 7. The key step 6 → 9 is a Pd-catalyzed, tandem intramolecular alkyne allylation/carbonylation reaction.
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  • 169
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The readily available alkyl dicyanoacetates 1 reacted with the 1,3-dipolar reagents arenecarbonitrile oxides 2′ and arenecarbonitrile imines 5′ to afford 1,2,4-oxadiazol and 1,2,4-triazol derivatives. The arenecarbonitrile oxides 2′ with electron-donating groups on the arene ring gave products 3a-d resulting from addition on both CN groups of 1, and those with electron-withdrawing groups provided mono-adducts 4a-e (Scheme 1). Arylnitrile imines 5′ reacted with 1 to offer both bis- and mono-addition products (Scheme 2); the bis-adducts 8a,b possess an ester structure, whereas the mono-adducts 6a-d present a ketene-hemiacetal structure.
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  • 170
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diels-Alder reactions of the (1H-indol-3-yl)-enacetamides and -endiacetamides 1a-d with some carbodieno-philes and 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione give rise to the novel amino-functionalized carbazole; 4-6 and 8 (Scheme 3). Ethenetetracarbonitrile reacts with 1b to furnish the Michael-type adduct 7 (Scheme 3). Structural aspects of the starting materials 1, which exhibit above all 3-vinyl-1H-indole reactivity, are discussed with regard to the prediction of a Diels-Alder process.
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  • 171
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ketene derivative of the chiral oxazolidinone 1 underwent non-concerted stereo specific [2 + 2] cycloadditions with the (Z)-imine moiety of diazepines 2, leading thereby with good diastereoselection to the trans-β-lactam adducts 3 (major) and 4 (minor). The absolute configuration of the major cycloadduct 3a was determined by an X-ray analysis. Its formation is discussed in terms of minimisation of steric interaction in the two transition states which give sequencially the zwitterionic intermediates and the final cycloadducts.
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  • 172
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of [Fe2(CO)9] with 2-exo,3-exo-bis(chloromethyl)-5,6-di(methylidene)-7-oxabicycio[2.2.1]-heptane (5) and with 5,6-di(methylidene)-7-oxabicyclo[2.2.1]heptane-2-exo,3-exo-dimethyl bis(methanesulfonate) (6) afforded, together with the corresponding [exo-Fe(CO)3(1,3-diene)] complexes 7 and 8, the products of dimerization in the form of stable [Fe(CO)2{(1,2,3-η:6,7,8-η)-octa-2,6-diene-1,8-diyl}] complexes 9 and 10, respectively, with high stereoselectivity. The structure of 10 was established by means of single-crystal X-ray diffraction.
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  • 173
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    Helvetica Chimica Acta 74 (1991), S. 904-904 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 174
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stereo and face selectivities of the cycloaddition of 1,2,3-trichloro-3-fluorocyclopropene (1a) with acyclic dienes and furans has been re-investigated by X-ray determination and correlation of 19F-NMR data. The isolated adducts of dienes exclusively have exo-configuration, and exo-Configuration predominates with furans. The Cl substituents of the resulting cyclopropane ring are cis-oriented. The face selectivity of the reaction with both types of substrates is attributed to electrostatic interactions between the F and the bridgehead Cl substituents, which destabilize the F-cis-transition state (13 (F-cis)) over 13 (F-trans).
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  • 175
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses of 1,7-dideaza-2′,3′-dideoxyadenosine (1) and related pyrrolo[2,3-b]pyridine 2′,3′-dideoxyribi and 2′,3′-didehydro-2′,3′-dideoxyribonucleosides (see 2-5) are described. As starting materials, 2′-deoxyribo-nucleosides 6 or 7 were used. The 3′-OH group was removed by Barton deoxygenation or via mesylation follow by elimination and catalytic hydrogenation. Compound 1 was also obtained from the direct glycosylation of 4-nitro-1H-pyrrolo[2,3-b]pyridine (17) with the 2,3-dideoxyribofuranosyl chloride 18. The triphosphate 25 of 1 showed only marginal activity against HIV-1 reverse transcriptase, indicating that purine N(1) is required for the inhibitory activity of the parent 2′,3′-dideoxyadenosine.
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  • 176
    ISSN: 0009-2940
    Keywords: Manganese-mediated cyclization ; Nine-membered carbocycles ; Manganese complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemical Reactions of Transition Metal Organyl Complexes with Olefines, 31). - [4 + 5] Cycloaddition of Conjugated Dienes to Tricarbonyl(η5-2,4-dimethyl-2,4-pentadienyl)manganeseTricarbonyl(η5-2,4-dimethyl-2,4-pentadienyl)manganese [1] reacts photochemically with the acyclic conjugated dienes 1,3-butadiene [A], 2-methyl-1,3-butadiene [B], (E)-1,3-pentadiene (C), (E,E)-2,4-hexadiene (D), 2,4-dimethyl-1,3-pentadiene (E), 2,4-hexadien-1-ol (F), and methyl 2,4-hexadienoate (G) in a formal [4 + 5] cycloaddition to give tricarbonylmanganese complexes with η3:2-2,6-cyclononadien-1-yl ligands (2A-2G). In addition, the reaction of 1 with A yields thermolabile [η3:2:2-1-(3-butene-1,2-diyl)-1,3-dimethyl-2,6-cyclononadiene]dicarbonylmanganese (3A) and E,E and E,Z isomers of [η3-1-(2-butene-1,1-diyl)-1,3-dimethyl-2,6-cyclononadiene]tetracarbonylmanganese (4A, 4A] as byproducts. Similarly, 1 reacts with B to form tetracarbonyl[η3-1-(3-methyl-2-butene-1,1-diyl)-1,3,6-trimethyl1-2,6-cyclononadiene]manganese (4B) in a side reaction. The crystal and molecular structures of tricarbonyl(η3:2-1,3,5,5,7-pentamethyl-2,6-cyclononadien-1-yl]manganese (2E) and of 3A are determined by X-ray structure analyses. In each of the formally octahedral complexes unusual long manganese-carbon bonds are found for one coordinated CC double bond of the hydrocarbon ligands.
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  • 177
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 17-23 
    ISSN: 0009-2940
    Keywords: (Borole)nickel complexes ; Nucleophilic substitution at boron ; 1H-Borole ; Dihydro-1H-borolediide ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Derivatives of Borole, XVI1), - Bis(borole)nickel Complexes2)The dilithium 1-(dialkylamino)dihydroborolediides Li2[C4H4-BNR2] 2a, b: R = Me, Et) react with NiCl2 · DME to give bis(borole)nickel complexes Ni(C4H4BNR2)2. Nucleophilic substitution reactions are used to produce a large variety of derivatives Ni(C4H4BR)2 1 (e.g. R = H, tBu, F, Cl, Br, I, OH, OMe). Treatment of Ni(C4H4BCl)2 (tg) with LiO(CH2)3OLi in THF produces a polymer and a dinuclear complex (μ-{η5:η5-[(CH2)3(OBC4H4)2]}2Ni2 (3) which crystallizes from CH2Cl2 as solvate 3 · CH2Cl2. The complexes 1g and 3 · CH2Cl2 are characterized by X-ray diffraction work. Barriers to internal ring-ring rotation are measured by variable-temperature NMR spectroscopy. The B - H bond of Ni(C4H4BH)2 (1a) is remarkably inert and does not react with H2O or with carboxylic acids in THF at room temperature. With PhCHO slow formation of the benzyloxy compound Ni(C4H4BOCH2Ph)2 (1 m) is observed at 100°C. For typical complexes such as the phenyl derivative 1e cyclic voltammetry in CH2Cl2 reveals an irreversible oxidation at 1.32 and a quasi-reversible reduction at -1.37 V vs. SCE.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 25-29 
    ISSN: 0009-2940
    Keywords: Borole complexes ; {η5-[1-(Diisopropylamino)borole]}metal complexes, internal rotation of, protonation of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Derivatives of Borole, XVII1). - {η5-[1-(Diisopropylamino)borole]}metal Complexes: Syntheses, Protonation, Internal RotationNew complexes M(CO)4L (M = Cr, W), cis-M(CO)2L2 [M = Mo, W (not isolated)], and (COD)NiL have been prepared from the Diels-Alder dimer L2, where L is 1-(diisopropylamino)borole, C4H4BNiPr2. Complexes of L can be protonated at the nitrogen atom to give stable salts such as [Cr(CO)4(LH)]BF4, [Fe(CO)3(LH)]BF4, [(C6Me6)Ru(LH)]BF4, and [CpCo(LH)]BF4; B  -  N bond dissociation is not observed. Barriers to internal rotation have been determined by variable temperature NMR spectroscopy for Cr(CO)4L, (COD)NiL, and NiL2. Three processes have been identified: rotation of the NiPr2 group around the B  -  N bond, gear-mesh rotation of the isopropyl groups around the C  -  N bonds, and rotation of L with respect to the counter ligands.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 51-61 
    ISSN: 0009-2940
    Keywords: Selenocarbonyl compounds, perfluorinated ; 1,3-Diselenetanes, perhalogenated ; 2-Selenabicyclo[2.2.1]hept-5-enes ; 1,3-Diselenetan-2-ylium hexafluoroarsenates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation of (Perfluoroalkyl)halogeno-1,3-diselenetanes from the Corresponding Selenocarbonyl Fluorides and Reactions with Boron Trichloride or Arsenic Pentafluoride1)Reactions of Hg(SeRt)2 (Rt = C2F5, C3F7, CF3) with (C2H5)2 All or All3 in octamethylcyclotetrasiloxane produce the unstable perfluoroalkaneselenocarbonyl fluorides 1 [R1 = CF3 (1 a), C2F5 (1 b), CF3Se (1 c)]. These compounds are very reactive and polymerize to rubberlike products. On heating the polymers decompose almost quantitatively to the monomers or dimers. In CFCl3 solution 1 dimerizes at 20°C in sunlight to the corresponding cis/trans-1,3-diselenetanes 2. The structure of 2 b is determined by single crystal X-ray diffraction. Different selenocarbonyl derivatives add to unsymmetrically substituted 1,3-diselenetanes 3. 1 a and 1 b react with cyclopentadiene to form the [4 + 2] cycloaddition products 4a and 4c. Halogen exchange reactions take place between 2a  -  d and BCl3. The cis-isomers react much faster than the trans-isomers to give a mixture of cis-, trans-forms of 5. When 2c,d is treated with BCl3 it is possible to isolate and characterize the pure trans-isomer 2d, which is separated by preparative gas chromatography from 5c,d. Fluorine abstraction with formation of 1,3-diselenetan-2-ylium ions (6a  -  f) are accomplished by reactions of 2 or 3 with AsF5 in SO2.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 87-88 
    ISSN: 0009-2940
    Keywords: Alkylidenesulfur difluoride oxide ; Carbon-sulfur double bond ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hg[C(COF) = SF2 = O]2 is prepared by the reaction of FCO — CH = SF2 = O with HgF2. This compound represents the third known example of an alkylidenesulfur difluoride oxide. Its molecular structure is the same as that of the most abundant of the three isomers of FCO-CH = SF2 = O. This is assumed to be the result of weak intramolecular Hg… O contacts. With the exception of the fluorine atoms bound to sulfur, all atoms lie approximately in one plane.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 103-109 
    ISSN: 0009-2940
    Keywords: Asteranes ; Cage compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Asteranes, XXII1).  -  Synthesis of a Double Tetraasterane: Nonacyclo[10.8.0.02,11.04,9.04,19.06,17.07,16.09,14.014,19]eicosane1,4,5,8-Tetrahydronaphthalene-2,3-dicarboxylic anhydride (9) is dimerized by UV light in dioxane yielding four isomeric [2 + 2] adducts whose methyl ester derivatives are elucidated spectroscopically. The structures of the major products 14 and 16 have been confirmed by X-ray structure analysis. Degradation of the carboxylic groups of 14 afforded the title compound 5.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 157-162 
    ISSN: 0009-2940
    Keywords: Fluoro compounds, aromatic ; Nitrite exchange by fluoride ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Aromatic Fluoro Compounds by Nucleophilic Exchange of Nitro Groups by FluorideThe synthesis of aromatic fluoro compounds from the respective nitro compounds by nucleophilic substitution of nitrite by fluoride is described. Reasonable yields in case of nonactivated nitro compounds are only obtained if the nitrite formed in the reaction is eliminated by acylation. 1-Fluoro-3-nitrobenzene (2) was obtained from 1,3-dinitrobenzene (1), and 1-fluoro-3,5-dinitrobenzene (9) as well as 1,3-difluoro-5-nitrobenzene (10) from 1,3,5-trinitrobenzene (8) in yields up to 92% by reaction of nitro compounds with potassium fluoride in sulfolane at 180 - 200°C in the presence of phthaloyl dichloride (6); 1,2-difluoro-4-nitrobenzene (12) was formed in 58% yield from 2,4-dinitro-1-fluorobenzene (11) in the presence of pyromellitoyl tetrachloride (13).
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 13-16 
    ISSN: 0009-2940
    Keywords: Diphosphines, tetrakis(diisopropylamino) ; Phosphinous anhydrides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Structure of Bis[bis(diisopropylamino)phosphino]chalcogenidesPhosphorodiamidous chalcogeno-anhydrides [(R2N)2P]2X (R = Me2CH; X = S, Se, Te) (2a-c) have been obtained by insertion of elemental sulfur, selenium, or tellurium into the P-P bond of the corresponding diphosphane (1). The structure of 2a and 2c has been confirmed by an X-ray diffraction.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 31-38 
    ISSN: 0009-2940
    Keywords: Fluorosulfonium salts, reaction with nucleophiles ; (Perfluoroakyl)(dimethylamino)sulfonium salts, preparation and structures of ; Methoxysulfinyl hexafluoroarsenate, alkylation with ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (Perfluoroalkyl)(dimethylamino)sulfonium HexafluoroarsenatesMeN = S(CF3)2 (5) is alkylated by Me3O⊕ AsF⊖6 to Me2N-S(CF3)⊕2 AsF⊖6 (4). From 5 and MeOSO⊕ AsF⊖6 (6) MeOS(O)-N(Me)S(CF3)⊕2 AsF⊖6 (7) is formed as a relatively stable primary product. Decomposition of 7 gives the expected 4 only in poor yield. Nucleophilic substitution of the sulfur-bonded fluorine in CF3SF⊕2 AsF⊖6 (8) by Me3SiNMe2 yields CF3S(NMe2)⊕2 AsF⊖6 (9). Similarly, (CF3)2CFSF⊕2 AsF⊖6 (10) reacts with dimethyl(trimethylsilyl)amine to give (CF3)2CFS(NMe2)⊕2 AsF⊖6 (11). The structures of 4 and 9 are elucidated by X-ray analyses, and the influence of the substituents on the bonding is discussed.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 63-67 
    ISSN: 0009-2940
    Keywords: Dinuclear gold complex ; Silyl complex ; Gold-gold interaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transition-Metal Silyl Complexes, 361).  -  On the Question of Gold-Gold Interactions in Ph2P[CH2]t(2)PPh2-Bridged Dinuclear Gold Silyl ComplexesDinuclear silyl gold complexes of the type dppm(AuSiR3)2 (1) or dppe(AuSiR3)2 (2) are prepared by the reaction of dppm-(AuCl)2 or dppe(AuCl)2 with two equivalents of LiSi(aryl)3 or LiSi(SiMe3)3 The complex dppe[AuSi(SiMe3)3]2 (2 c) exhibits crystallographic inversion symmetry, and therefore the distance between both gold atoms is a maximum. In dppm-(AuSiPh3)2 (1b) a gold-gold interaction between both gold atoms is observed [Au  -  Au 316.80(3) pm].
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 149-156 
    ISSN: 0009-2940
    Keywords: Cyclobutene, ring-opening ; Poly Diels-Alder reaction ; Molecules, double-stranded ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclobutene Ring Opening: A Useful Reaction for the Synthesis of Double-Stranded MoleculesSyntheses and ring-opening reactions of the compounds endo-5a - e and 9a - c, all containing cyclobutene rings, are described. From these experiments it is concluded that compound 9a is a useful AB-type Diels-Alder monomer for the synthesis of well-defined double-stranded molecules. The stereochemistry of the adducts endo-4b and endo-5d is determined by X-ray structure analysis.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 175-184 
    ISSN: 0009-2940
    Keywords: α-Enones, regioselective 1,2-addition of dimethyl phosphite to ; Allylic rearrangement of dialkyl (1-hydroxy-2-alkenyl)phosphonates ; 1-Alkenylphosphonates, 3-acetyloxy- ; 1-Alkenylphosphonates, 3-hydroxy- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of Dialkyl Phosphites with α-Enones, I. - Synthesis and Allylic Rearrangement of Dimethyl (1-Hydroxy-2-alkenyl)- and (1-Hydroxy-2-cycloalkenyl)phosphonatesVarious β,γ-unsaturated α-hydroxyphosphonates 3 are prepared in good yields by NaOCH3-catalyzed regioselective 1,2-addition of dimethyl phosphite to acyclic and cyclic α-enones at -35°C. On acid-catalyzed acetylation, the allylic α-hydroxyphosphonates 3 (R1, R2 + H) rearrange under thermodynamic control; yielding the new 3-acetyloxy-1-(cyclo)alkenyl derivatives 8, from which the transposed allylic alcohols 11 are readily obtained. Using shorter reaction times, acetylation of compounds 3 affords mixtures of 1- and 3-acetylated products, 10 and 8, respectively.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 207-212 
    ISSN: 0009-2940
    Keywords: 2,3,6-Trioxypentafulvenes ; Keto-enol tautomerism ; Push-pull system ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of 2,3,6-trioxypentafulvenes with a free position at the ring are described, in which the protection of the C-3 hydroxy group as methoxy or acetoxy derivative has been required. The difference in the behavior of the title compounds in relation to the previously reported 1,4-disubstituted 2,3,6-trihydroxypentafulvenes 2a-e, which only exhibit enol forms, is discussed and attributed to the disappearance of the push-pull system formed by the C-3 enol group and the C-4 electron-withdrawing substituent.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 233-235 
    ISSN: 0009-2940
    Keywords: Hexaoxacyclotriacontadodecaenes ; Macrocycles ; 2,2-Bis(2-furyl)propane ; 2,5-Bis[1-(2-furyl)-1-methylethyl]furan ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New O6 Macrocycles with 2,2-Bis(2-furyl)propane UnitsThe macrocycles 3a and 6 are prepared in 29 and 16% yield by cyclization of dilithiated 2,2-bis(2-furyl)propane (1) and 2,5-bis[1-(2-furyl) 1-methylethyl]furan (5), respectively, with ethyl N,N-dimethylcarbamate (2).
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 237-240 
    ISSN: 0009-2940
    Keywords: Bicyclo[3.2.1]oct-6-yl cations ; Wagner-Meerwein rearrangements ; Alkyl-bridged ions ; Conformational effects ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rearrangements of 1,4,4- and 2,2,5-Trimethylbicyclo[3.2.1]oct-6-yl Cations1,4,4-Trimethylbicyclo[3.2.1]oct-6-yl cations (18) are generated from the tosylhydrazone 7, by nitrous acid deamination of the amines 6 and 8, and by acetolysis of the brosylates 21 and 24. The product distributions are but slightly affected by the configuration (exo vs. endo) of the leaving groups. The predominant product, 1,4,4-trimethylbicyclo[3.2.1]octan-exo-6-ol (11) is formed without significant redistribution of a 6-2H label. The degenerate Wagner-Meerwein rearrangement of the parent bicyclo[3.2.1]oct-6-yl cation is virtually eliminated by the presence of two methyl groups at C-4. Enhanced conformational strain, raising the barrier to ring flipping, accounts for these observations. Minor products (12, 13) arise from a 7,6-hydride shift of 18, followed by Wagner-Meerwein rearrangement. When the 2,2,5-trimethylbicyclo[3.2.1]oct-6-yl cation (19) is generated directly from the tosylhydrazone 17, the tertiary alcohol 13 is obtained as the major product. The conformational barrier to Wagner-Meerwein rearrangement is compensated by the incipient stabilization of the tertiary carbocation 20.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 403-405 
    ISSN: 0009-2940
    Keywords: 1,2-Dihydropentalenes ; 1,5-Dihydropentalenes ; Rearrangements ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An efficient one-pot synthesis of 3-substituted 1-phenyl-1,2-dihydropentalenes from α,β-unsaturated ketones is described. These compounds can be rearranged to their 1,5-dihydro isomers using different methods such as acid catalysis and vacuum-flash thermolysis or by chromatography on alumina.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 417-421 
    ISSN: 0009-2940
    Keywords: Methylenephosphines ; Voltammetry, cyclic ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electrochemical investigations on a selection of methylenephosphines 1 and related systems are reported. They are shown to possess an irreversible oxidation and reduction wave. An exception is diaminodiphosphene, which reversibly forms a radical anion. A relative ordering of frontier orbitals is possible, based on the redox properties of these systems.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 321-327 
    ISSN: 0009-2940
    Keywords: Trifluororthocarbonates of potassium, rubidium, cesium ; Phase transitions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Crystal Structures of Potassium, Rubidium, and Cesium Trifluororthocarbonate and a Remark Concerning the Barium Sulfate Type1)Crystals of potassium, rubidium, and cesium trifluororthocarbonate (9a, 9b, and 9c) have been grown by Ostwald ripening in CH3CN applying a COF2 pressure of 3 bar. According to X-ray single-crystal structure analysis, 9a, 9b, and 9c belong to the baryte-structure family with an pseudotetrahedral anion being dynamically disordered at room temperature. All of the title compounds undergo a phase transition into a monoclinic, completely ordered low-temperature form, which has been refined for 9c. The C - O bond seems to be shortened by polar interactions. The results obtained with 9a, 9b, and 9c at room temperature indicate that the type of disorder found in 9 might be generally present in baryte-type compounds.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 339-345 
    ISSN: 0009-2940
    Keywords: Photoadditions ; Caffeine derivatives ; Calculations, AM1 ; Diradicals ; Propellanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selectivities in Photoadditions with Multifunctional Caffeine DerivativesElectronically excited stilbene (21*), 4,4′-dichlorostilbene (1*), and 4,4′-dimethoxystilbene (18*) are trapped by caffeine derivatives 2, 13, or 22 with variable results. While 1* and 2 react predominantly at the imino double bond (substitutive and fragmentating additions), 1* or 18* and 13 produce mostly propellanes by [2 + 2] photocycloaddition, which hydrolyze or may be hydrolyzed. 21* and the relatively electron-poor compound 22 produce mostly propellanes, which always show a preponderance of the syn-10, anti-11 stereoisomers. These selectivities as well as the competition with reactions at the imino double bonds are rationalized on the basis of diradical mechanisms with the aid of semiempirical AM1 calculations. Earlier results on closely related transformations are also discussed.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 377-381 
    ISSN: 0009-2940
    Keywords: Phosphorus compounds, organic ; Phosphorus heterocycles ; Arbuzov rearrangement ; Mechanism, SN2, SN1 ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Addition Reactions of Phosphorus Nucleophiles to BenzothieteTrialkyl phosphites 4 add to the o-quinoid form 2 of benzothiete (1) to yield the phosphonates 6. An intermolecular migration of an alkyl group from oxygen to sulfur is the most important feature of this transformation. The rearrangement - related to the Arbuzov reaction - can be avoided in a two-step process by the subsequent action of PCl3 and alcohol; thus the phosphonates 10 are generated. Analogous to 2 → 6, dimethyl phenylphosphinate (11) furnishes 13. In contrast, the cyclic esters 14a-d form 2:1 adducts, namely the 12- to 15-membered heterocyclic compounds 17a - d. An intramolecular rearrangement in a 1:1 adduct is only observed for the 1,3,2-dioxaphosphepine 14e, a benzylic system which allows an SN1 process generating the 1,6,2-oxathiaphosphecine 18e. A similar rearrangement at a tertiary carbon center is prevented by the competitive addition of water (1 + 14f → 20).
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 391-396 
    ISSN: 0009-2940
    Keywords: Ozonolysis ; Cycloalkylidenecycloalkanes ; Dispiro-1,2,4-trioxolanes ; Thermolysis ; Photolysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dispiro-1,2,4-trioxolanes by Ozonolysis of Cycloalkylidenecycloalkanes on PolyethyleneOzonolyses of symmetrical (1b - d) and of unsymmetrical cycloalkylidenecycloalkanes (8a, b) afforded the dispiro-1,2,4-trioxolanes 4b - d and 9a, b, respectively. Their thermal decompositions gave mixtures of the cyclic ketones (3) and lactones (6). Photolyses afforded in addition to 3 and 6 the cyclic anhydrides 13, which are isomeric with the corresponding dispiro-1,2,4-trioxolanes.
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    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 665-669 
    ISSN: 0009-2940
    Keywords: Semideltic acid ; Cyclopropenylium cations ; Pseudooxocarbon anions ; Semideltate anions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pseudooxocarbon Anions of Semideltic AcidNovel pseudooxocarbon anions of semideltic acid (2) can easily be obtained by stepwise substitution of the dimethylamino groups of the cyclopropenium perchlorate 8. Treatment of 8 with cyanamide or malononitrile in the presence of triethylamine leads to the triafulvenes 9 and 13. Two cyanoimino groups are successfully introduced into the cyclopropenylium system by treating 9 with excess cyanamide/potassium ethoxide. Under the same conditions malononitrile reacts with 13 to yield the potassium salts 14 and 17. The thioamide 26 of semideltic acid is obtained by treating the triphenylphosphonium salt 24 with H2S/pyridine and subsequent hydrolysis of the intermediate 25. With the anions of cyanamide or malononitrile ring-opening reaction of the cyclopropenylium system of 24 occurs to yield the push-pull phosphonium salts 28 and 29.
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  • 198
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    Keywords: Ethylene-bridged metal complexes ; Ethanediyl complexes ; Manganese, Rhenium, Ruthenium, Osmium carbonyls ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrocarbon-Bridged Metal complexes, XVIII. - Heterometallic Ethylene-Bridged Complexes (OC)5ReCH2CH2Mn(CO)5, (OC)5ReCH2CH2Ru(CO)2Cp, (OC)5ReCH2CH2Os(CO)4CH2CH2Re(CO)5 and (OC)5ReCH2CH2CH2Os(CO)4Os(CO)4(CO)4Os(CO)4CH2CH2Re(CO)5Addition of [(OC)5Re(C2H4)]+ to the carbonylmetallates [Mn(CO)5]-, [RuCp(CO)2]-, [Os(CO)4]2-, [Os3(CO)12]2- affords the title complexes in a directed way. The dynamic behaviour of (OC)5ReCH2CH2Mn(CO)5 in solution is attributed to a dyotropic exchange of the pentacarbonylmetal groups on the CH2CH2 bridge.
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    Keywords: [2.2.2]Paracyclophane ligand ; (η6)π Complexes ; Arsenic(III) complexes ; Antimony(III) complexes ; Bismuth(III) complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Arsenic(III), Antimony(III), and Bismuth(III) Trihalide Complexes of [2.2.2]Paracyclophane: From Weak van der Waals Coordination to Strongly Directional π Complexation with Single or Double External η6 Coordination[2.2.2]Paracyclophane forms the adducts C24H24·AsCl3 (1), C24H24·(SbCl3)2·1/2 C6H6 (2), and C24H24·(BiCl3)3·C6H6 (3). For solutions in polar solvents NMR spectra indicate extensive dissociation and/or fluxionality. In the crystals adduct 1 features a weak addition of the AsCl3 molecule to one open side of a paracyclophane molecule with long intermolecular contacts approaching C3v symmetry. - Crystalline 2 shows SbCl3 coordination to two of the benzene rings of the hydrocarbon in a quasi-centered η6 mode, while one of the benzene rings remains uncoordinated. Chlorine-bridging between antimony atoms leads to tetrameric units (SbCI3)4 in the lattice. - In the bismuth compound 3 each benzene ring of the hydrocarbon is engaged in centroid (η6)π complexation, with the BiCl3 units crosslinked by chlorine bridges. The average of the Bi-ring distances (3.08,2.98, and 2.99 Å) is shorter than for the Sb-ring distances in 2 (3.047 and 3.050 Å), indicating stronger bonding. The crystal benzene is not coordinating.
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  • 200
    ISSN: 0009-2940
    Keywords: Metallacyclic organoaluminium, -gallium and -indium compounds ; MOVPE precursors ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intramolecularly base-stabilized four-coordinated metallacyclic organoaluminium, -gallium, and -indium compounds C5H10-Al(CH2)3NMe2 (4), C4H8Ga(CH2)3NMe2 (5), C5H10Ga(CH2)3N-Me2 (6), C5H10GaCH2CH(Me)CH2NMe2 (7), C4H8Ga(CH2)4NMe2 (8), C5H10Ga(CH2)4NMe2 (9), EtAl[(CH2)3]2NMe (10), MeGa-[(CH2)3]2NMe (11), EtGa[(CH2)3]2NMe (12), MeIn[(CH2)3]2NMe (13), and (14) have been synthesized by the reaction of [3-(dimethylamino)propyl]aluminium dichloride (1), [3-(dimethylamino)propyl]gallium dichloride (2), [3-(dimethylamino)-2-methylpropyl]gallium dichloride (3), or [4-(dimethylamino)butyl)gallium dichloride with the respective bis-Grignard reagents or by the reaction of the organometal dichlorides RMCl2 with bis[3-(chloromagnesio)propyl]methylamine or with N,N′-bis[3-(chloromagnesio)propyl]-N,N′-dimethyl ethylenediamine. Aluminium or gallium trichloride reacts with tris[3-(chloromagnesio)propyl]amine to give Al[(CH2)3]3N (15) and Ga[(CH2)3]3N (16). The 1H-, 13C-NMR and mass spectra of the new compounds as well as the X-ray crystal structure of 16 are discussed. 4, 6, and 12 have been tested successfully as MOVPE precursors.
    Additional Material: 2 Ill.
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