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  • Inorganic Chemistry  (10,736)
  • 1990-1994  (3,613)
  • 1970-1974  (3,865)
  • 1950-1954  (1,627)
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  • 201
    Electronic Resource
    Electronic Resource
    Carbon-Carbon Bond Cleavage of the [2.2]Paracyclophane Radical Cation Generated by Electron Transfer Oxidation with Cerium(IV) Ammonium Nitrate (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 875-879 
    Details
    ISSN: 0009-2940
    Keywords: [2.2]Paracyclophanes ; Electron transfer reactions ; Radicals ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Single electron transfer (SET) oxidation of [2.2]paracyclophane (1) with cerium ammonium nitrate (CAN) produces the corresponding radical cation (1+.), which undergoes cleavage of the carbon-carbon bond of the ethano bridge to generate the double-benzylic radical cation 2+. Trapping of this intermediate by oxygen and nucleophiles gives rise to aldehydes 3, while a second oxidation and subsequent nucleophilic trapping affords nitrates 4. This facile cleavage of the carbon-carbon bond is explained by alignment of the latter with the π systems in the rigid structure of [2.2]paracyclophane, which enables charge delocalization across both benzene rings. When the reaction is carried out in methanol, aromatic substitution takes also place as a minor reaction pathway, which is responsible for the formation of the polyfunctionalized cyclophane 5d.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270514
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  • 202
    Electronic Resource
    Electronic Resource
    Michael Addition of Imines to Alkynylcarbene Complexes with Subsequent Intramolecular Cyclization - An Efficient Three-Step Synthesis of 2H-Pyrroles (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 911-920 
    Details
    ISSN: 0009-2940
    Keywords: Chromium, [2-(methyleneamino)ethenyl]carbene complexes ; Michael addition of imines ; (1-alkynylcarbene)-chromium complexes ; 2H-Pyrroles ; Cyclization of {[2-(methyleneamino)ethenyl]carbene}chromium complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Imines 7, 11-13 were added to (1-alkynylcarbene)chromium complexes 6a-d to form {[2-(methyleneamino)ethenyl]-carbene}chromium complexes 8a-d, 14a-d, 15a-d, 16a-d in good to very good yields (63-98%) except for two cases (41-59%). The carbene ligands of the latter compounds cyclize to 2H-pyrroles 9a-d, 17a-d, 18a-d, 19a-d upon heating in tetrahydrofuran solution to 50-55°C.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270520
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  • 203
    Electronic Resource
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    Graphical Abstract (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. A53 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270528
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  • 204
    Electronic Resource
    Electronic Resource
    Effect of Fluorine and Chlorine Substituents on Stabilities of Diphosphaallene, Diphosphirene, and Phosphanylphosphaalkyne Isomers (XX′ CP2 Species with X, X′ = H, F, and Cl) (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 969-978 
    Details
    ISSN: 0009-2940
    Keywords: Diphosphaallenes ; 1H-Diphosphirenes ; 3H-Diphosphirenes ; Phosphanylphosphaalkynes ; Calculations ; ab initio MO ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio MO calculations at the QCISD(T)/6-31G* */MP2/6-31G* * + ZPE level on the XX′CP2 isomers (X = H1 F and Cl) show that the energies of the isomeric species are often reordered following halogen substitution. The phosphorushalogen moiety behaves as the main stabilizing factor on the rest of the molecular structure. This is particularly true when X = F is involved. In the dihalogenated series phosphanyl-phosphaalkyne (4) becomes the most stable species followed by diphosphaallene (3) and 1 H-diphosphirene (6). The effect on the geometry following halogenation is larger if substitution takes place at carbon than at phosphorus. The behaviour of the P species is found to be quite different from, if not opposite to, that of their nitrogen analogues. Finally, the infrared spectra of the most stable isomers are also predicted.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270602
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  • 205
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    Bis(trifluormethylsulfonyloxy)organosilicium-Verbindungen als Synthesebausteine für neuartige Siliciumpolymere (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 985-990 
    Details
    ISSN: 0009-2940
    Keywords: Silyl triflates ; Polysiloxanes ; Polycarbosilanes ; Polysilylenealkynes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis(trifluoromethylsulfonyloxy)organosilicon Compounds as Synthetic Materials for New Silicon PolymersThe new polycarbosilanes, polysiloxanes, and polysilylenealkynes 1c-6c were obtained by condensation of electrophilic α,ω-bis(trifluoromethylsulfonyloxy)organosilicon compounds 1b-6b with nucleophiles such as organolithium and organomagnesium compounds. The required silyl triflate derivatives 1b-6b have been prepared by reaction of the corresponding amino-, allyl-, or phenylsilanes 1a-6a with trifluoromethanesulfonic acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270604
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  • 206
    Electronic Resource
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    Komplexe mit makrocyclischen Liganden, II. Synthese, Struktur und elektrochemische Eigenschaften eines makrocyclischen Cu2IIMnII-Komplexes vom Schiff-Basen-Typ (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 991-995 
    Details
    ISSN: 0009-2940
    Keywords: Copper(II) complexes ; Mangan(II) complexes ; trinuclear ; Schiff bases ; macrocyclic ; Redox properties ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complexes with Macrocyclic Ligands, II.  -  Synthesis, Structure and Electrochemical Properties of a Macrocyclic Cu2IIMnII Complex of Schiff Base TypeA novel trinuclear Cu2Mn complex 4 of a macrocyclic Schiff base ligand obtained by condensation of 5-tert-butyl-2-hydroxy-1,3-benzenedicarbaldehyde with 1,2-phenylenediamine was synthesized. The molecular structure of 4 was determined by X-ray diffraction revealing a sandwich-type structure as depicted by Figure 2. Electrochemical investigations (DCV measurements) showed two one-electron reduction steps for the copper ions at E1/2 = -1.383 and -1.652 V (vs. Cp2Fe/Cp2Fe+).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270605
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  • 207
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    Chemie polyfunktioneller Molekule, 112. Ringerweiterungsreaktionen an einem neuartigen spirocyclischen Cobaltaphosphazen mit Sauerstoff, Schwefel und SelenHerrn Prof. Dr. Ekkehard Lindner zum 60. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1015-1020 
    Details
    ISSN: 0009-2940
    Keywords: Ring enlargement reactions ; Spirocyclic cobaltaphosphazene ; Eight-membered carbon-free inorganic rings ; Tetrahedral CoE4 core (E = O, S, Se) ; Phosphazenoid skeleton ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemistry of Polyfunctional Molecules, 112.  -  Ring Enlargement Reactions of a Spirocyclic Cobaltaphosphazene with Oxygen, Sulfur, and SeleniumHerrn Prof. Dr. Ekkehard Lindner zum 60. Geburtstag gewidmet.The spirocyclic cobaltaphosphazene 1 which contains cobaltconnected three-, five-, and six-membered rings undergoes ring enlargement reactions by treatment with O2, S8, and Se8. The resulting paramagnetic spirocyclic cobalta-phosphazenoids 2a-c (E = O, S, Se) consist of eight-membered chelate rings connected at the spiro-cobalt(II) centre forming a tetrahedral CoE4 core. The compounds 2a-c have been characterized by X-ray analyses, 1H, 13C(1H), 31P(1H) NMR, IR, Raman, UV/Vis/NIR, EI/FD mass spectroscopy, and magnetic measurements.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270608
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  • 208
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    Pentamethylcyclopentadienyl-substituiertes Selenadiphosphiran und Selenatriphosphetan: Synthese, Struktur, Dynamik und einige ReaktionenHerrn Prof. R. Schmutzler zum 60. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 997-1001 
    Details
    ISSN: 0009-2940
    Keywords: Selenadiphosphiranes ; Selenatriphosphetanes ; Molecular dynamics ; Phosphacycles ; Selenium compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pentamethylcyclopentadienyl-Substituted Selenadiphosphirane and Selenatriphosphetane: Synthesis, Structure, Dynamic, and Some ReactionsHerrn Prof. R. Schmutzler zum 60. Geburtstag gewidmet.1,2,3-Tris(pentamethylcyclopentadienyl)cyclotriphosphane (1) reacts with selenium to form the insertion product 2,3,4-tris(pentamethylcyclopentadienyl)selenatriphosphetane (2), which is trapped as the selenium-coordinated pentacarbonylchromium complex 4. Compound 4 is the first isolated selenatriphosphetane complex. Reaction of 2 with selenium yields 2,3-bis(pentamethylcyclopentadienyl)selenadiphosphirane (3). 3 replaces thf of Cr(CO)5thf to give the chromium complex 5. The reaction of 3 with K[Fe(CO)2Cp*] leads to the substitution product 6 and the bicyclic phosphane 7. The X-ray structures of 3 and 4 are presented. The dynamic behavior of 3-6 is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270606
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  • 209
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    Evidenz für eine Struktur-Reaktivität-Beziehung bei sperrig substituierten Lithium(fluorsilyl)phosphaniden (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1031-1035 
    Details
    ISSN: 0009-2940
    Keywords: Lithium-(fluorosilyl)phosphanides ; Phosphanides, lithium-(fluorosilyl)(phosphanyl)- ; Silylidenephosphanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Evidence for a Structure-Reactivity Relationship of Crowded Substituted Lithium (Fluorosilyl)phosphanidesThe molecular structures and the reactivity of the new solvated lithium (fluorosilyl)phosphanides 1a, 2a, and 2b has been investigated. The unusual solid state structures of 1a and 2b are established by X-ray crystallography. Whereas the lithium centre in 1a is bound to phosphorus and solvated by three molecules of THF, the electronical saturation of the lithium centre in 2b is achieved by a Li—P bond, tridentate chelatization (fluorine, phosphorus, nitrogen), and the additional coordination of one molecule of THF. The trigonal-planar geometry at phosphorus in 1a is unprecedented for derivatives of this type and reflects the steric demand around the phosphorus and the possibility of πp/σ*sic hyperconjugation. The Si—P bond lengths [P—SiC(Phenyl) 2.186(2) and P—SiF 2.164(2) Å] are significantly shorter than in related pyramidally configurated derivatives (1b, c: P—SiC 2.21, P—SiF 2.18 Å). Both phosphorus atoms in 2b are pyramidally coordinated, but the intramolecular chelate coordination of the lithium centre causes much smaller bonding angles at the Si—P phosphorus atom [sum of bonding angles 238.4(2) (PSi), 312.5(1)° (PN)]. 1a as well as 2a, b show quite different reactivity as compared to 1b-d due to their unusual structures. Heating of solutions of 1a and 2a, b in toluene or hexane does not give the expected stable silylidenephosphanes (Si=P) by elimination of LiF. Instead, rearrangement reactions of the Si=P intermediates 6, 8 lead to the new heterocycles 5, 9. A single-crystal X-ray diffraction analysis of 5 has been performed. The Si2P2 cyclobutane ring is planar, and the NMe2 groups at the ring silicon atoms are cis-orientated.  -  Interestingly, 2b eliminates LiNiPr2 at 20°C in a kinetically controlled process to form the tetraphosphacyclobutane 7 as the major product. Presumably, the diphosphene 8 is an intermediate in this reaction.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270610
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  • 210
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    3,4-Dimethylenborolane und 3,7-Diborabicyclo[3.3.0]oct-1(5)-ene (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1037-1039 
    Details
    ISSN: 0009-2940
    Keywords: Borolanes ; Boroles, 2,5-dihydro ; 3,7-Diborabicyclo[3.3.0]oct-1(5)-enes ; 2,5-Diborapentalenes, 1,2,3,4,5,6-hexahydro- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3,4-Dimethyleneborolanes and 3,7-Diborabicyclo[3.3.0]oct-1(5)-enesThe tetramethyleneethane derivative K2[C2(CH2)4] which is readily prepared from 2,3-dimethylbutadiene by metallation with the Lochmann-Schlosser base reacts with BC12(NR2) (R=Me, Et, iPr) to give the highly reactive, liquid 1-(dialkylamino)-3,4-dimethyleneborolanes (3). These dienes react with activated magnesium to give soluble magnesium adducts 5 which upon treatment with BC12(NR2) (R = Me, iPr) yield crystalline 3,7-bis(dialkylamino)-3,7-diborabicyclo-[3.3.0]oct-1(5)-enes (4). The crystal structure of the dimethyl-amino compound 4a was determined by X-Ray-diffraction. The molecule of 4a shows crystallographic C2h symmetry with an almost perfectly planar skeleton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270611
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  • 211
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    Studien zur C—H-Aktivierung, X. Synthese von Alkyl(carbonyl)hydrido- und Allylhydrido-Osmiumkomplexen durch Metall-initiierte Fragmentierung von primären Alkoholen und OlefinenHerrn Professor Dr. E. Lindner zum 60. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1021-1029 
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    ISSN: 0009-2940
    Keywords: Osmium(II) complexes ; Alkyl(carbonyl)hydrido complexes ; Allylhydrido complexes ; Fragmentation, metal-initiated ; C—H Activation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies on C—H Activation, X.  -  Synthesis of Alkyl(carbonyl)hydrido- and Allylhydridoosmium Complexes by Metal-initiated Fragmentation of Primary Alcohols and OlefinsHerrn Professor Dr. E. Lindner zum 60. Geburtstag gewidmet.The reaction of [(Mes)OsCl2]n (1) with RCH2OH/NaOH in the presence of propene leads to complete fragmentation of the primary alcohol and formation of the alkyl(carbonyl)hydrido complexes [(Mes)OsH(R)(CO)] (2-7). The corresponding chloro derivatives [(Mes)OsC1(R)(CO)] (8-13) are obtained either by H/C1 exchange from 2-7 and CC14 or on treatment of [(Mes)OsR2(CO)] (16-21) with HC1 at -78°C. The carbonylosmium(II) compound [(Mes)Os(CO)C12] (15) reacts with iC4H9MgI to give a mixture of [(Mes)Os(iC4H9)2(CO)] (21), [(Mes)OsI(iC4H9)(CO)] (22), and [(Mes)Os(CO)I2] (23), whereas the reaction of 15 with C6H11CH2MgBr yields [(Mes)Os(CH2C6H11)2(CO)] (24), the olefin complex [(Mes)Os(CH2=C6H10)(CO)] (25), and [(Mes)OsH(Br)(CO)] (26). The alkylhydridoosmium(II) compound [(Mes)OsH(CH2C6H11)(CO)] (28) is obtained from the chloro derivative 27 and Mg/Hg/C2H5OH. Treatment of 1 with iC3H7OH/NaOH and propene or isobutene affords the η3-allylhydrido complexes [(Mes)OsH(η3-2-RC3H4)] (31, 32) in about 85% yield, while the reaction of 1 with iC3H7OH/NaOH and tert-butylethene gives [(Mes)Os(CH2=CHtC4H9)2] (35). The X-ray structural analysis of [(Mes)OsH(η3-2-CH3C3H4)] (34), which like the corresponding η3-allylchloro compound 33 is formed from the η3-allylhydrido complex 31 or 32 and CC14, reveals a half sandwich-type structure with an exo arrangement of the methallyl ligand.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270609
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  • 212
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    Cyclische isomere vier- und fünfgliedrige heterodinucleare Fischer-Carbenkomplexe  -  gebildet aus einem Vinylidentitanocen-Fragment und Metallcarbonylen (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1003-1013 
    Details
    ISSN: 0009-2940
    Keywords: Metallocene complexes, bent ; Titanium complexes ; Vinylidene complexes ; Transition metal complexes ; Heterodinuclear complexes ; Carbene complexes ; Early-Late heterodinuclear complexes ; Metallacycles ; Oxatitanacyclobutane complexes ; Oxatitanacyclopentene complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclic Isomeric Four- and Five-Membered Heterodinculear Carbene Complexes  -  Formed from a Titanocene Vinylidene Fragment and Metal CarbonylsThe four-membered heterodimetallic carbene complexes Cp*2 16 [LnM: Cr(CO)5 (a), Mo(CO)5 (b), W(CO)5 (c), CpRe(CO)2 (f), Mn2(CO)9(g), Re2(CO)9 (h), Fe(CO)4 (i), Rh(acac)(CO) (i)] are easily prepared by trapping the vinylidenetitanocene [Cp*2Ti=C=CH2] fragment 6 with the corresponding metal carbonyls. The vinylidenetitanocene 6 is generated in a favourable manner from Cp*2Ti(CH3)CH=CH2 (13) or Cp * (Fv)TiCH = CH2 (14) [Fv: C5(CH3)4CH2] by a 1,3-H shift (α elimination) at room temperature. The formation of 16 is characterized by a preferred suprafacial [2 + 2] cycloaddition. Starting from Cp*2 (5) or 14 and transition metal carbonyls unexpected isomeric five-membered titanacycles Cp*2 8 [MLn = a-c, MnCp(CO)2 (d), MnCp′(CO)2 (e), f-i] are obtained at higher temperatures (70-100°C). These oxatitanacyclopentenes 8 are formed also upon heating via the kinetic product 16 with high yield, as a result of a 1,2-hydrogen shift, proved for c, g, h. From the spectroscopic data an η1-vinylcarbene structure is deduced, exhibiting a cis- (16) or trans-configurated (8) LnM=C—C=C sequence. An X-ray structure analysis shows the importance of the acyl resonance form in 8a, typically observed for such heterodimetallic carbene complexes. The reversible liberation of the metal carbonyl is a remarkable property of complexes 16 in solution, whereas the thermodynamic product 8 shows the typical properties of Fischer carbene complexes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270607
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  • 213
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    Reaktive E=C(p-p)n-Systeme, XXXVIII. Molekül- und Elektronenstruktur des 2-(Diisopropylamino)-1λ3-phosphaethins iPr2NC≡P (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1041-1045 
    Details
    ISSN: 0009-2940
    Keywords: λ3-Phosphaalkyne, 2-amino- ; PE Spectroscopy ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactive E=C(p-p)π-Systems, XXXVIII.  -  Molecular and Electronic Structure of 2-(Diisopropylamino)-1λ3-phosphaethyne iPr2NC≡PThe molecular structure of 2-(diisopropylamino)-1λ3-phosphaethyne iPr2NC≡P (3) has been investigated by X-ray diffraction using a single crystal grown from the melt at -50.2°C. Bond distances and angles indicative for the electronic structure are: P°C 155.2(2), N—C(sp) 131.2(3) pm, P—C—N 179.2(2)°; with a sum of angles 359-8° the nitrogen atom has a trigonal-planar coordination. The reported geometrical parameters of 3 have been reproduced by ab initio calculations (3-21G and DZP basis), showing that the lengthening of the P°C and the shortening of the C—N bond can be rationalized by the interaction of the π system of the triple bond with the 2p orbital at N. The He(I) photoelectron spectrum of 3 confirms the strong interaction.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270612
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  • 214
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    Synthese und Struktur von 5,6,11,12-Tetrakis(diisopropylamino)-5,6,11,12-tetra-hydrodibenzo[c,g][1,2,5,6]tetraborocinHerrn Prof. Dr. Gottfried Märkl zum 65. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1047-1048 
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    ISSN: 0009-2940
    Keywords: 1,2-Benzodiborete, 1,2-dihydro- ; Dibenzo[c,g][1,2,5,6]tetraborocine, 5,6,11,12-tetrakis(diisopropylamino)- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Structure of 5,6,11,12-tetrakis(diisopropylamino)-5,6,11,12-tetrahydrodibenzo[c,g][1,2,5,6]tetraborocineHerrn Prof. Dr. Gottfried Märkl zum 65. Geburtstag gewidmet.Catalytic dimerization of 1,2-bis(diisopropylamino)-1,2-dihydro-1,2-benzodiborete (1) with (phthalocyanine)palladium [Pd(pc)] leads to the eight-membered title compound 2 in 95% yield. An X-ray structure analysis of 2 exhibits a chair conformation for the central C4B4 ring (folding angle along B1B2/B1′B2′ 55.5°).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270613
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  • 215
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    Stereoselectivity of the Transfer of Hydrogen Atoms to Cyclic Alkyl Radicals (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1069-1073 
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    ISSN: 0009-2940
    Keywords: Free-radical additions ; Alkyl radicals ; Stereoselectivity ; Hydrogen transfer ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of cyclohexane to alkylmaleic anhydrides 1a-f via cyclic radicals 2a-f gave a mixture of (Z)- and (E)-2,3-dialkylsuccinic anhydrides 3a-f. The stereoselectivity of the hydrogen transfer from cyclohexane to radicals 2a-d was measured in the temperature range of 200-260°C, and the relative activation parameters of the formation of (Z)- and (E)-3 were determined. The stereoselectivity of the hydrogen transfer from cyclohexylmercuric hydride at 25°C was measured as well. The results are rationalized assuming steric interactions in the transition state of H donor and β substituent and of α and β substituent, respectively. An X-ray structure analysis of the highly strained addition product (Z)-3d was performed.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270616
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  • 216
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    New Cyclopropyl Building Blocks for Organic Synthesis, 21. Diels-Alder Reactions of Methyl 2-Chloro-2-cyclopropylideneacetate with Electron-Rich Dienes: Synthesis of Potential Intermediates for Illudin M (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1051-1064 
    Details
    ISSN: 0009-2940
    Keywords: Cyclopropyl building blocks ; Strained compounds ; [4 + 2] Cycloaddition ; Regioselectivity ; Epoxides, regioselective cleavage of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Ethoxy- (8a) and 1-(trimethylsilyloxy)-1,3-pentadiene (8b) cycloadded to 2-chloro-2-cyclopropylideneacetate 6 to give low yields of endo/exo-9a and -9b, respectively. On the other hand, furans 5a-d added 6 (5b and 5d reacted regioselectively) to afford mixtures of the corresponding [4 + 2] cycloadducts endo-11a-d and exo-11a-d in good to high yields. 2-Methyl-5-(trimethylsilyloxy)furan (5e) yielded a mixture of the four cycloadducts endo/exo-11e and endo/exo-12e, which upon attempted purification on silica gel underwent facile hydrolysis to give bicyclic hemiacetals endo/exo-13 and 4-hydroxycyclo-2-hexen-1-ones endo/exo-14, respectively. Similarly endo/exo-11f, and endo/exo-12f, obtained from 2-methoxy-5-methylfuran (5f) and 6, upon hydrolysis in the presence of silica gel gave endo/exo-13 and endo/exo-14 respectively. The structures of endo-14 and exo-12f were established by X-ray crystallography. In the presence of florisil, the epoxides endo-and exo-16 were formed from trimethylsilyloxy-substituted cycloadducts endo/exo-11e. Selective reduction of the α-chlorocarboxylate functionality in the cycloadducts endo-11a-d,f with LiBH4, followed by base-catalyzed cyclization of the resulting chlorohydrins endo-21a-d, f yielded the corresponding epoxides endo-22a-d,f in 22-73% overall yield. Under identical conditions, the cycloadducts exo-11a-f could not be reduced to the corresponding chlorohydrins exo-21a-f. Regioselective reduction of the acetal epoxide endo-22f to the tertiary alcohol endo-23f was achieved with sodium dihydrobis(2-methoxyethoxy)aluminate (Red-Al®). On stirring with moist silica gel, the bicyclic acetals endo-22d,f and endo-23f cleanly hydrolysed to the highly substituted spiro[2.5]oct-6-en-5-ones endo-24d,f (26 and 24% overall yields, respectively, in four steps from 5d,f and 6) and endo-25f, respectively (23% overall yield in five steps from 5f and 6).
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270614
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    Liquid-Crystalline D-Glucose Dialkyl Acetals and Dodecyl D-Glucofuranosides (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1065-1068 
    Details
    ISSN: 0009-2940
    Keywords: Acetals ; Amphiphiles ; Carbohydrates ; Glucosides ; Liquid crystals ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new systems of liquid crystalline glucose derivatives 5a-d, 6a, b are prepared, studied and compared with reference compounds. The α- and β-D-dodecyl glucofuranosides 6a, b show smectic A phases. The clearing points of the furanosides are of the same magnitude as those of the pyranosides. The alkyl glucose acetals 5a-d show columnar discotic phases. The clearing points are about 30°C lower than those of the corresponding thioacetals.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19941270615
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    Structure of Octamethylene-Bridged Derivatives of 1,3-Cyclohexadiene and Bicyclo[3.1.0]hexene (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1091-1093 
    Details
    ISSN: 0009-2940
    Keywords: anti-Bredt Olefins ; Bicyclo[8.2.2]tetradeca-1(13),11-diene ; Photocyclization ; Tricyclo[8.2.2.012,13]tetradec-10-ene ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and photochemical generation of the octamethylene-bridged 1,3-cyclohexadiene and bicyclo[3.1.0]hexene derivatives 1 and 2, which are to be classified as anti-Bredt olefins, are reported. out Orientation of the octamethylene bridge at the sp3-hybridized bridgehead atom of 1 generates strain effects while in orientation of the bridge in 2 does not give rise to deformations of the bicyclo[3.1.0]hex-2-ene subunit. X-ray analyses indicate a twisted double bond (12.2 and 15.0°) at the bridgehead atom of 1 and a deformation of the six-membered ring from an ideal boat conformation. In contrast, the five-membered ring of compound 2 is planar. The folding angle between the five- and the three-membered ring is 111.8(2)°. The olefinic carbon atoms of 1 are slightly pyramidalized.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270618
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    Iron-Catalyzed Coupling of Tricyclo[4.1.0.02,7]hept-1-ylmagnesium Bromide and Related Grignard Reagents with Propargylic and Allylic HalidesDedicated to Prof. Dr. Helmut Quast on the occasion of his 60th birthday. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1075-1089 
    Details
    ISSN: 0009-2940
    Keywords: Cross coupling ; iron-catalyzed ; Propargylbicyclo[1.1.0]butanes ; Allenylbicyclo[1.1.0]butanes ; Allylbicyclo[1.1.0]butanes ; [4.1.1]Propella-2,4-diene ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several uncatalyzed and transition metal-catalyzed cross coupling reactions of the Grignard compounds 1c or 2c with propargylic or allylic halides were investigated. Fe(acac)3 was the most effective catalyst for the preparation of allyl-and propargylbicyclo[1.1.0]butanes 7 and 5. In the latter case, the formation of the isomeric allenylbicyclo[1.1.0]butanes 6 was also observed. Stereoelectronic factors of substituents like a trimethylsilyl group as a directing group could be utilized for the formation of either 5 or 6. A number of bicyclo[1.0.0]butanes 15-21 with two substituents in the bridgehead positions were accessible by that route as well. In the case of the bis-allenyl compound 24c, an ene-type reaction leading to the first known derivative of a [4.1.1]propella-2,4-diene 25 was observed. Base-catalyzed isomerizations of the propargylbicyclo[1.1.0]butanes 5 opened a new route to alkynylbicyclo[1.1.0]butanes 30-32.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19941270617
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    Thianthrene 5-Oxide (SSO) as a Mechanistic Probe of the Electrophilic Character in the Oxygen Transfer by Dioxiranes (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1111-1113 
    Details
    ISSN: 0009-2940
    Keywords: Thianthrene 5-oxide ; Dioxiranes ; Hydrogen peroxide ; Oxidation ; Oxygen transfer ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thianthrene 5-oxide (SSO) is established as a useful and convenient chemical probe to assess the electronic character (Xso) of oxygen transfer agents. Thus, H2O2 under basic conditions (HOOH/nBu4NOH) gives an Xso value of 1.00, while H2O2 under acidic conditions (HOOH/HClO4) affords an Xso value near zero. On this Xso scale, dimethyldioxirane (Xso = 0.13 at 0°C) and methyl(trifluoromethyl)dioxirane (Xso = 0.10 at 0°C) are, as expected, definitely strong electrophilic oxidants.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19941270621
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    Thermolabile Hydrocarbons, 33. Thermochemistry and Thermal Decomposition of 9,9′-Bifluorenyl and 9,9′-Dimethyl-9,9′-bifluorenyl - The Stabilization Energy of 9-Fluorenyl Radicals (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1095-1103 
    Details
    ISSN: 0009-2940
    Keywords: Heats of formation ; Bond cleavage ; C—C ; kinetics of ; Radicals ; stability of ; Correlation between heats of vaporization and solvent-accessible surfaces ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: From thermochemical measurements the heats of formation ΔH0f(g) forfluorene (1), 9-methylfluorene (2), 9,9′-bifluorenyl (5), and 9,9′-dimethyl-9,9′-bifluorenyl (6) were determined. The homolytic cleavage of the dimers 5 and 6 to 9-fluorenyl (3) and 9-methyl-9-fluorenyl radicals (4), respectively, was studied in mesitylene with thiophenol as trapping agent and found to follow first-order kinetics. The activation parameters ΔH≠(5) = 212.6 (±2.1) kJ mol-1, ΔS≠(5) = 70.3 (±4.2) J mol-1 K-1 ΔH≠(6) = 164.9 (±0.7) kJ mol-1, and ΔS≠(6) = 88.2 (±1.9) J mol-1 K-1 were obtained. For 3 and 4 the radical stabilization energies RSE(3) = 67 (±7) kJ mol-1 (relative to isopropyl) and RSE(4) = 64 (±8) kJ mol-1 (relative to tert-butyl) were determined by a comparison with the activation parameters of the thermolysis of alkanes possessing the same strain enthalpy. The heats of formation for 3 and 4 and the C-H bond dissociation energies for the C-H bond in the 9-position of 1 and 2 were determined to be ΔH0f(g,3) = 300 kJ mol-1, Δ0f(g,4) = 268 kJ mol-1, BDEC—H(1) = 343 and BDEC—H(2) = 338 kJ mol-1 (estimated errors correspond to those of the RSE values). A good correlation between the heats of vaporization of 37 aromatic hydrocarbons and their calculated solvent-accessible surfaces was demonstrated. Hence, a new method to estimate heats of vaporization was established.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270619
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    Transanular Interactions in Difunctional Medium Rings, 5. Spectroscopic Investigations of Bicyclic Boraamines (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1105-1110 
    Details
    ISSN: 0009-2940
    Keywords: 3-Borabicyclo[3.3.1]nonanes ; 7-[(dialkylamino)methyl]- ; 2-Azonia-1-boratatricyclo[4.3.1.14,8]undecanes ; Borane-amine complex formation ; Photoelectron spectra ; Conformational analysis ; Transanular interaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The endo-7-[(dialkylamino)methyl]-3-borabicyclo[3.3.1]nonanes 1 and 2 have been synthesized and their intramolecular complex formation of the corresponding 2-azonia-1-boratatricyclo[4.3.1.14,8]undecanes 3 and 4 has been studied in the gas phase by UV photoelectron spectroscopy and in solution by 11-NMR spectroscopy. Deviations of the characteristic spectral features from those of the monofunctional bicyclic boranes 5 and amines 6 and 7 indicate that in the gas phase the (dimethylamino)boranes with a B-alkyl substituent adopt the tricyclic form 3a-c whereas the diethylamino and the B-methoxy derivatives 1e and 2 prefer the bicyclic structure. In solution some deviations from this behavior are observed.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270620
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    Syntheses of Zindoxifene and Analogues by Titanium-Induced Oxo-Amide Coupling (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1125-1130 
    Details
    ISSN: 0009-2940
    Keywords: Indoles, 2-aryl- ; Titanium graphite ; Zindoxifene ; Tumor-growth inhibitors ; Alkylidenation, intramolecular ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Highly reactive titanium on graphite is used to reductively cyclize electron-rich acylamino carbonyl compounds 7, 8, 12, 14, and 16 to the corresponding indole derivatives 9, 10, 13, 15, and 17. Compound 9b is a known precursor of the mammary tumor-inhibiting compound zindoxifene (2). The other products are new analogues of this anticancer drug, exhibiting the substitution pattern previously recognized to be essential for high pharmacological activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270624
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    syn-ar,ar′-Difluorometacyclophanes: Strong 19F,19F Spin - Spin Interactions Transmitted through SpaceDedicated to Prof. Dr. Albrecht Mannschreck on the occasion of this 60th birthday. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1119-1124 
    Details
    ISSN: 0009-2940
    Keywords: Difluorometacyclophanes ; syn-Metacyclophanes ; Through-space F,F spin coupling ; X-ray structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The close approach of the fluorine nuclei in the difluorinated syn-[3.3]metacyclophanes 1, 2 and their [2.2] analogues 3, 4 leads to strong 19F,19F spin-spin interactions which obey a through-space mechanism. The geometries of 1-4 were estimated by MM2 molecular mechanics computations, those of 1 and 3 were also determined by X-ray structural analyses. The decrease of the F,F internuclear distance in the series 1, 2, 3, 4 (2.78-2.48 Å) correlates with an increase of J(FF) from +42.1 to +99.2 Hz. It follows that, for a given distance d(FF), J(FF) is up to twice as large as a previous empirical correlation has assumed and even larger with respect to earlier theoretical calculations. Only weak F,F spin interaction occurs in 8, the anti isomer of 4.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270623
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    Preparation of 2H-Benzoxetes by Photoinduced [2 + 2] Cycloaddition of Quinone Methides, Accessible by Dimethyldioxirane (DMD) Oxidation of 2,3-Dimethylbenzofurans (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1115-1118 
    Details
    ISSN: 0009-2940
    Keywords: Epoxidation ; Dioxirane, dimethyl- ; Benzofurans, 2,3-dimethyl- ; Benzofuran epoxides ; Quinone methides ; [2 + 2] Photocycloaddition ; Benzoxetes ; Hetero-Diels-Alder reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Irradiation (λ 〉 366 nm) of the quinone methides 3, which were formed by valence isomerization of the methyl-, chloro-, and tert-butyl-substituted 2,3-dimethylbenzofuran epoxides 2, afforded the novel 2H-benzoxetes 4 by photochemical [2 + 2] cycloaddition. These strained and highly labile benzoxetes 4 were spectrally (1H and 13C NMR) characterized at subambient temperatures. On prolonged storage (2-3 d) at -20 to -10°C, the benzoxetes 4 reverted to the quinone methides 3 and/or benzofuran epoxides 2.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19941270622
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    Synthese von 6,6-Dimethylfulven-2-carbonsäure-methylester und -2,3-dicarbonsäure-dimethylester sowie deren Umsetzung zu 2,3,5,6-substituierten Nordbornadienen (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1143-1145 
    Details
    ISSN: 0009-2940
    Keywords: Fulvenes ; Norbornadienes ; Cycloadditions ; Diels-Alder reactions ; Pyrolysis, flash vacuum ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Methyl 6,6-Dimethylfulvene-2-carboxylate and Dimethyl 6,6-Dimethylfulvene-2,3-dicarboxylate as well as their Reaction to 2,3,5,6-Substituted NorbornadienesFulvenes 5 and 6 were synthesized by Diels-Alder reaction of 6,6-dimethylfulvene with methyl prop-2-ynoate and dimethyl but-2-ynedioate, catalytic reduction of the unsubstituted norbornadiene double bond, and a subsequent retro Diels-Alder reaction under flash vacuum pyrolysis conditions, 5 and 6 are used as the diene component in synthesizing 2,5-, 2,3,5-, and 2,3,5,6-substituted norbornadienes 7-9 by Diels-Alder reaction with electron-deficient alkynes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270627
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    Cycloallene, 9. 1-Phenyl-1-aza-3,4-cyclohexadien, das erste Isodihydropyridin: Erzeugung und Abfangreaktionen (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1137-1142 
    Details
    ISSN: 0009-2940
    Keywords: Isoquinolines, hexahydro- ; Cyclobuta[c]pyridines, hexahydro- ; Cycloadditions, [2 + 2]- and [4 + 2]- ; 3-Azabicyclo[3.1.0]hexane, 6,6-dibromo-3-phenyl- ; 2,4-Pentadienylamine, 3-n-butyl-N-phenyl- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cycloallenes, 9.  -  1-Phenyl-1-aza-3,4-cyclohexadiene, the First Isodihydropyridine: Generation and InterceptionThe generation of the title cycloallene 4 from 6,6-dibromo-3-phenyl-3-azabicyclo[3.1.0]hexane (10) with methyllithium according to the Doering-Moore-Skattebøl method is reported. In the presence of styrene, 1,3-butadiene, furan, 1,3-cyclohexadiene, and 1,3-cyclopentadiene, 4 is intercepted in [2 + 2] and [4 + 2] cycloadditions with formation of the hexahydrocyclobuta[c]pyridines 6 and 11 and the hexahydroisoquinolines 12-15, respectively. The starting compound 10 is prepared via the cis-disubstituted 1,1-dibromocyclopropanes 8 and 9 from the known dioxepine derivative 7, the synthesis of which has been considerably improved. On treatment with n-butyllithium, the dichlorophenylazabicyclohexane 3 is converted into 4 as well. However, in the competition for 4, styrene is not successful against n-butyllithium, which transforms 4 into the pentadienylamine 5.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19941270626
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    Darstellung, Struktur und konformatives Verhalten gespannter Adamantanophane (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1147-1156 
    Details
    ISSN: 0009-2940
    Keywords: Adamantanes ; Adamantanophanes ; Cyclophanes ; Ring strain ; Sulfone pyrolysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation, Structure, and Conformational Behaviour of Strained AdamantanophanesExchange of aromatic units (e.g. benzene) for aliphatic/alicyclic building blocks (e.g. adamantane) in cyclophanes leads to new molecules of the “araliphane” type. In the framework of this concept the araliphanes 3(a), 5-7a, 10(a), and 11 are synthesized. Their stereochemical behaviour differs significantly from that of their aromatic counterparts as shown by NMR studies and X-ray crystallographic analyses. Extremely upfield-shifted signals of the intraanular adamantane hydrogen atoms are found as well as a planar chiral adamantanophane. A Diels-Alder addition of 8 to the benzene ring of 6 yields 9. Complete replacement of benzene units by adamantane leads to the fully aliphatic/alicyclic “aliphanes”. The crystal structure of 15 is described.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270628
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    Tin for Organic Synthesis, 11. A Mild and Effective Synthesis of α,β-unsaturated Carboxamides and Sulfonamides by Electrophilic Substitution of Alkenylstannanes with Isocyanates (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1131-1136 
    Details
    ISSN: 0009-2940
    Keywords: Electrophilic vinylic substitution ; Isocyanates ; α,β-Unsaturated amides, synthesis of ; Carbodestannylation ; Alkenylstannanes, applications of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new and effective method for the preparation of a variety of olefinic carboxamides 6a-k and N-(4-methylphenyl-sulfonyl) carboxamides 7a-d is described. The reaction of aryl and alkyl isocyanates 4a-c or 4-methylphenylsulfonyl isocyanate 5 with 1-alkenyltrialkylstannanes 1a-e and di-1-alkenyldibutylstannanes 2a-c in the presence of aluminium trichloride provides the corresponding N-aryl-substituted olefinic carboxamides 6a-k or the N-(4-methylphenyl-sulfonyl)-substituted olefinic carboxamides 7a-d in good yields. The stannyl moiety is superior to hydrogen as a leaving group and enables electrophilic ipso substitution at the vinylic system. In the case of di-1-alkenyldibutylstannanes the substitutions are also stereospecific, whereas the reactions of 1-alkenyltrialkylstannanes with isocyanates proceed with partial isomerisation.
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    URL: http://dx.doi.org/10.1002/cber.19941270625
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    A Convenient Synthesis of New Macrocyclic NaphthalenophanesDedicated to Professor E. V. Dehmlow on the occasion of his 60th birthday. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1157-1162 
    Details
    ISSN: 0009-2940
    Keywords: Cyclophanes ; Naphthalenophanes ; McMurry reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The (1,4)naphthalenophanes 6a, 6b, 7a, and 7b were synthesized regiospecifically in two steps from the appropriate α,β-di-1-naphthylalkanes by a Friedel-Crafts acetylation of the two naphthalene groups followed by cyclization/dimerization of the resulting diketones by a McMurray reaction. The macrocyclic naphthalenophanes 6a and 6b exist in solution as a mixture of conformers while 7a and 7b were identified as the anti isomers.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270629
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    Dibenzo[18]annulenes Incorporating Two Diphenylhexatriene Units (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1167-1170 
    Details
    ISSN: 0009-2940
    Keywords: Annulenes ; Chromophores ; Hexatrienes ; Hydrocarbons ; Macrocyclic compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [6.6]cyclophanehexaene hydrocarbon 6a and the dimethoxy[6.6]cyclophanehexaene 6b are prepared starting with the unsaturated diacid 1. An X-ray analysis of 6a exhibits a planar molecular skeleton. NMR and optical data prove a not fully conjugated macrocyclic π system and its division into two largely separate chromophores.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270631
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    A Convenient Synthesis of Macrocyclic[2.1.2.1]Paracyclophanes (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1163-1166 
    Details
    ISSN: 0009-2940
    Keywords: Cyclophanes ; Coupling reaction ; McMurry reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [2.1.2.1]paracyclophanedienes 9-11 were prepared in good yields by a McMurry cyclization of the bis(4-acylphenyl)methanes 5 and 6 and of bis(4-acetylphenyl) ether (7), respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270630
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    Characterization of Neutral and Ionic Sulfur - Nitrogen Cluster Molecules NS2 and NS3 in the Gas Phase (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1171-1173 
    Details
    ISSN: 0009-2940
    Keywords: Tandem mass spectrometry ; Collision experiments ; Sulfur-nitrogen clusters ; Electron transfer ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Collision experiments on NS-x (x = 2, 3) clusters are reported. Evidence is presented for the gas-phase existence of the corresponding NS.x and NS+x species. For x = 3, the mass spectra are very much in keeping with a connectivity SS-NS (5) for all three charge states. For x = 2, the experimental data favor the presence of NSS (2); however, the cyclic C2v-symmetric form 3 cannot be ruled out.
    Additional Material: 4 Ill.
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    Masthead (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270701
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    Graphical Abstract (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. A65 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270633
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    α-Mercurio-Substituted Phosphorus Ylides: A Simple Route to Vinylmercury CompoundsDedicated to Prof. H. J. Bestmann (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1177-1183 
    Details
    ISSN: 0009-2940
    Keywords: Phosphorus ylides ; Olefination reactions ; Mercury compounds ; Vinyl compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of novel α-mercurio-substituted phosphorus ylides, Ph3P=CR[HgN(SiMe3)2] 3a-d (R = Me, Et, iPr, Ph) is easily accomplished by mixing equivalent amounts of a phosphorus ylide 1a-d with Hg[N(SiMe3)2]2 in an inert solvent. These organometallic compound are completely characterized including an X-ray analysis of 3a. Their reaction with benzaldehyde yields vinylmercury amides (E)/(Z)-PhHC=CR[HgN(SiMe3)2] 4a-d. In reactions involving 3a-c the stereochemistry [favored formation of (E)-4a (≍;72 - 83%) and (Z)-4b, c (≍60 - 73%)] in the absence of a lithium salt is contrary to the stereochemistry of the established Wittig olefination reaction with non-stabilized phosphorus ylides like 1a-d. From the reported results, the preliminary conclusion is drawn that the stereochemistry is mainly controlled by steric interactions. Only in one case a remarkable salt effect is observed. When 3c reacts with benzaldehyde in the presence of LiBr and THF as solvent up to 95% of (E)-4c is formed. The semistabilized ylide 3d gives under all conditions studied a 50:50 mixture of (E)/(Z)-4d. The vinylmercury amides 4a, c are cleaved by hydrous NaOH to yield divinyl-mercury compounds (E,E)-(PhHC=CR)2Hg and (Z,Z)-(PhHC=CR)2Hg (R = Me: 7a; R = iPr: 7c). The compound 4d is cleanly cleaved by NaBH4 in hydrous 3 M NaOH to yield a 50:50 mixture of cis- and trans-stilbene (8).
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    URL: http://dx.doi.org/10.1002/cber.19941270702
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    Konstitution und Farbe von Alizarin- und Purpurin-Farblacken (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1185-1190 
    Details
    ISSN: 0009-2940
    Keywords: Dyes ; Colour and constitution ; Halochromism ; Alizarin ; Purpurin ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Constitution and Colour of Alizarin and Purpurin DyesThe colour of madder dyes used as pigment in antiquity and in the last centuries is produced mainly by metal complexes of alizarin (1) and purpurin (2). Single crystals of aluminium calcium alizarinate and purpurinate are obtained by two-phase crystallization. X-ray structure determinations show tetranuclear complex molecules with four alizarins which are different from formerly proposed structures. Solutions of 17 metal complexes of alizarin in DMF/Water exhibit UV-Vis spectra the maxima of absorption of which strongly depend on the electronegativity of the metals. A classical explanation for this is given.
    Additional Material: 6 Ill.
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    Chelat-stabilisierte 1,3-Bis(acyloxy)-1,3-diethyldiboroxane aus Triethylboroxin und Carbonsäureanhydriden115. Mitteilung über Borverbindungen.  -  114. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1191-1199 
    Details
    ISSN: 0009-2940
    Keywords: Ethylboronic carboxylic acid anhydrides, comproportionation of ; Bicyclo[3.3.1]nonadienes, heteroatom-containing ; Bicyclo[3.3.3]undecadienes, heteroatom-containing ; 1,3,2-Diboroxanes ; Oxygen atom exchange ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chelate-Stabilized 1,3-Bis(acyloxy)-1,3-diethyldiboroxanes from Triethylboroxin and Carboxylic Acid AnhydridesTriethylboroxin (A) reacts with carboxylic acid anhydrides (RCO)2O [R = Me: 1a; Et: 1b; tBu: 1d; Ph: 1e] with various rates to give high yields of the 3,7-dialkyl-1,5-diethyl-4,8,9-trioxa-2,6-dioxonia-1,5-diboratabicyclo[3.3.1]nona-2,6-dienes OB(Et)OC(R)OB(Et)OC(R)O (2) [R = Me: 2a (X-ray crystal structure analysis); Et: 2b; tBu: 2d; Ph: 2e], presumably via the unstable compounds OB(Et)OB(Et)OC(R)OB(Et)OC(R)O (3a,b, d, e). Compound 1c (R = CF3) reacts with A to form a mixture of 1,3-diethyl-1,3-bis(trifluoroacetoxy)diboroxane O=C(CF3)OB(Et)OB(Et)O(CF3)C=O (2c′) and 2c (R = CF3) at room temperature. Whereas two compounds of the type 2 do not comproportionate, 1a-e spontaneously form the mixed substituted carboxylic acid anhydrides 1ab etc. on mixing at room temperature (GC, 13C NMR). - From the 17O-enriched A* and 1a-e the 17O-enriched compounds 2a*-e* with BO*B and YYBO*OCR groups are obtained. A* exchanges O atoms up to 200°C with succinic anhydride (1f) forming 1f* or with phthalic acid anhydride (1g) forming 1g* and 3g*. - The mixed carboxylic acid anhydrides 1xy are cleaved, and the mixtures of 1 are separated with A to yield the uniform 3,7-dialkyl-substituted compounds 2.
    Additional Material: 2 Ill.
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    Ein einfacher Weg zu Silicium in oktaedrischer Sauerstoffkoordination (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1213-1218 
    Details
    ISSN: 0009-2940
    Keywords: Silicon ; Octahedral oxygen coordination ; Phosphorus ; NMR, 1H MAS ; NMR, 29Si MAS ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Simple Route to Silicon in Octahedral Oxygen CoordinationSyntheses and crystal structures of three new compounds Rb2SiP4O13 (1), Cs2H2Si(P2O7)2 (2), and BaH2Si(P2O7)2 (3) containing silicon in an octahedral oxygen coordination are reported. The structures have been determined by X-ray structure analyses. All three compounds are constituted of silicophosphate polyanions. The NMR chemical shifts of silicon and hydrogen are measured.
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    URL: http://dx.doi.org/10.1002/cber.19941270706
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    1,3-Diaza-2λ2-phosphonia-4λ4-gallatacyclobutane (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2397-2401 
    Details
    ISSN: 0009-2940
    Keywords: [Amino(imino)phosphane]gallium trichloride adduct ; 1,3-Diaza-2λ2-phosphonia-4λ4-gallatacyclobutanes ; Nickel tricarbonyl complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,3-Diaza-2λ2-phosphonia-4λ4-gallatacyclobutanesReaction of amino(imino)phosphanes 1a-c with gallium trichloride results in the formation of 1,3-diaza-2λ2-phosphonia-4λ4-gallatacyclobutanes 3a, b with elimination of chlorotrimethylsilane (1a) or tert-butyl chloride (1b, c). The intermediately formed amino(imino)phosphane/Lewis acid adducts R(Me3Si)NPN(GaCl3)R′ (2, R,R′ = tBu, Me3Si) can be isolated in the case of compound 2a (R = R′ = SiMe3). A diazaphosphasilacyclobutane - gallium trichloride adduct 4 is formed in a side reaction by isomerization of 2a. Reaction of compound 3b with Ni(CO)4 gives the corresponding transition metal complex 5. The NMR data and X-ray structures of compounds 2a, 4, and 5 are reported.
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    URL: http://dx.doi.org/10.1002/cber.19941271210
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    Komplexierung von 1,4-Dihydro-1,4-diborafulvenen mit Ni(cod)- und Pt(cod)-FragmentenHerrn Professor Hubert Schmidbaur zum 60. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2393-2396 
    Details
    ISSN: 0009-2940
    Keywords: 1,4-Diborafulvenes, 1,4-dihydro- ; Slipped triple-decker ; Nickel complexes ; platinum complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complexation of 1,4-Dihydro-1,4-diborafulvenes with Ni(cod) and Pt(cod) Fragments*Reactions of the 1,4-diborapentafulvene derivatives 1 and 2a, b with M(cod)2 (M = Ni, Pt) yield the complexes [(η5-1)Ni-(cod)] (8), [(μ,η2η5-2a){Ni(cod)}2] (9a), [(μ,η2,η5-2b){Ni(cod)}2] (9b), and [(μ,η2,η5-2a){Pt(cod)}2] (10). Compounds 9 and 10 are the first examples of complexes with 2a, b as a μ,η2,η5-ligand. The X-ray structure analyses of 9b and 10 are described.
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    URL: http://dx.doi.org/10.1002/cber.19941271209
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    One-Electron Oxidation of Aryltriazenes to Radical Cations (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2423-2429 
    Details
    ISSN: 0009-2940
    Keywords: Triazenes, aryl ; Radical cations ; Cyclic voltammetry ; ESR spectroscopy ; UV-Vis spectroelectrochemistry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3,3-Dimethyl-1-(4-R-phenyl)- [R = (CH3)2N, C2H5O, CH3O, CH3; 3] and 3-Methyl-1-(4-R1-phenyl)-3-(4-R2-phenyl)triazenes [R1 = (CH3)2N, CH3O, NO2, R2 = CH3O, H, 4] are oxidized electrochemically and chemically to their one-electron oxidation products. Cyclic voltammograms of the triazenes are discussed, and ESR as well as UV/Vis spectra of the radical cations are presented. The stability of the triazene radical cations generated depends on the substituents on the aryl rings. 4-R-Benzenediazonium ions are identified as one of the decay products of the radical cations by means of cyclic voltammetry and UV/Vis spectroelectrochemistry.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941271213
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    Propellane, 10[1] Bis- und Tris(propellane) aus Methylbenzolen: 1,2;3,4;5,6-Tris{8′,11′-dioxa[4.3.3]propella(3′,4′)}benzol (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2471-2474 
    Details
    ISSN: 0009-2940
    Keywords: Propellanes, bis- and tris- ; Polycyclic compounds ; Hexamethylbenzene ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Propellanes, 10[1]. - Bis- and Tris(propellanes) from Methylbenzenes: 1,2;3,4;5,6-Tris{8′,11′-dioxa[4.3.3]propella(3′,4′)}benzeneThe synthesis of the title tris(propellane) 17, derived from hexamethylbenzene, and bis(propellane) 12 is reported. Some aspects of the conformation of the compounds 12 and 17 are studied by 1H-NMR spectroscopy. Compound 17 exists as an equilibrium of two conformers with C3 and C1 symmetry. In the case of propellane 10, the formation of an isomeric bispirane compound is discussed.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19941271217
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    Face-Selective and endo-Selective Cycloadditions with Enantiomerically Pure Cyclopentadienes (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2505-2509 
    Details
    ISSN: 0009-2940
    Keywords: Cyclopentadienes, bicyclic ; Face selectivity ; endo selectivity ; Chiral discrimination ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general synthetic route to the enantiopure bicyclic cyclopentadienes (S)-3 and (R)-3 of the hydrindane series, starting from the Hajos-Wiechert ketone 4 or its enantiomer is described. Reasons for the excellent face and endo selectivity of cycloadditions and the resulting consequences for chiral recognition are discussed.
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    URL: http://dx.doi.org/10.1002/cber.19941271223
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    Stereoselective Synthesis of Alcohols, XLVIII[1] Linear Synthesis of (9S)-Dihydro-Erythronolide A (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2519-2526 
    Details
    ISSN: 0009-2940
    Keywords: Erythronolide A ; Allylboration, stereoselective ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Starting from building block 3 comprising the C-7 to C-15 segment of erythronolide A, a linear synthesis of erythronolide A has been achieved. Key steps were a Sharpless-epoxidation to set up the sterocenter at C-6, and two stereoselective allylboration reactions to generate the stereocenters at C-2, C-3, C-4, and C-5.
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    URL: http://dx.doi.org/10.1002/cber.19941271225
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    Palladium-Catalysed Multiple Coupling Reactions of β-Bromostyrene with Norbornene and Dicyclopentadiene (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2539-2541 
    Details
    ISSN: 0009-2940
    Keywords: Palladium catalysis ; Heck reactions ; Domino coupling reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (E)-β-Bromostyrene [(E)-2] reacts with norbornene (1a) or dicyclopentadiene (1b) in the presence of Pd(OAc)2, K2CO3, and nBu4NBr in DMF to yield a mixture of the 2:1 coupling products 4 and 5, while (Z)-β-bromostyrene [(Z)-2] gives exclusively 5. Under analogous conditions, (Z)-3-iodoacrylic acid (6) reacts with norbornene (1a) to give the diene 11 with an exo, exo-2,3-disubstituted norbornane skeleton.
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    URL: http://dx.doi.org/10.1002/cber.19941271229
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    Structure of the cis and trans Isomers of 2,4-Bis(diethylamino)-1,5-dimethyl-1,5,2,4-diazadiphosphorinan-6-one 2,4-Disulfide (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1247-1249 
    Details
    ISSN: 0009-2940
    Keywords: 1,5,2,4-Diazadiphosphorinane-6-one, cis-trans isomerism of ; 1,5,2,4-Diazadiphosphorinan-6-one, 2,4-disulfides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 2,4-bis(dialkylamino)-1,5-dimethyl-1,5,2,4-diazadiphos-phorinan-6-ones 1a and 1b (R = CH3, a; C2H5, b) are thermally unstable and are transformed into the bicyclic species 2 when heated to 150°C (2 Torr). The reactions of 1a and 1b with elemental sulfur lead to the P,P′-disulfides 4a and 4b as a mixture of cis and trans isomers which are separated by column chromatography. Single-crystal X-ray structure determinations were conducted on compound 2 and on the cis and trans isomers of 4b. The bicyclic compound 2 is found to display crystallographic twofold symmetry. Its structure is closely similar to that of the diphenyl analogue. For the cis and trans isomers of 4 almost ideal S-P…P-S torsion angles are observed. The isomers adopt different ring conformations.
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    URL: http://dx.doi.org/10.1002/cber.19941270711
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    Synthese mittlerer und großer Ringe, XXXVI. Synthese eines überbrückten, in-konfigurierten Bicyclo[2.1.0]pentan-Derivates (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1263-1267 
    Details
    ISSN: 0009-2940
    Keywords: Photochemistry ; Stereoselective bromination ; Deoxygenation ; Allyl-Cyclopropyl ring closure ; 2D-NMR ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Medium and Large Rings, XXXVI.  -  Synthesis of a Bridged Bicyclo[2.1.0]pentane Derivative with inside ConfigurationDihydrocyclobutafurans 4 (H instead of Br) are reactive intermediates in the photochemical rearrangement of 3,6-hexanooxepine-4,5-dicarboxylic esters. The synthesis of the bromo derivative 4 was achieved by irradiation of the epoxyoxepine 1 followed by a regio- and stereoselective NBS bromination of 2 and deoxygenation of 3 with tungsten hexachloride/n-butyllithium. Treatment of the allylic bromide 4 with sodium methoxide gave surprisingly the title compound 5. The structure of 5 was established by thorough NMR analysis.
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    URL: http://dx.doi.org/10.1002/cber.19941270714
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    Selected Transformations of 6-Cyclopropylidene-5-oxaspiro[2.3]hexan-4-one, a Highly Strained Tricyclic β-Lactone (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1275-1281 
    Details
    ISSN: 0009-2940
    Keywords: Ketenes (dimeric) ; reactions with nucleophiles and electrophiles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title lactone 2 acylates a variety of amines including phenylalanine, sterically hindered alcohols, and phenols. With activated non-enolizable carbonyl compounds, bis-spiro 6-membered β-keto lactones are formed. Oxidative rearrangement of 2 affords bis-spiro lactones 12 and 13.
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    URL: http://dx.doi.org/10.1002/cber.19941270716
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    Acid-Induced Stereoselective Formation of 3,5-Cycloheptadien-1-ones from Ketenes and DienesDedicated to Prof. C. Rüchardt on the occasion of his 65th birthday. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1269-1274 
    Details
    ISSN: 0009-2940
    Keywords: Ketene cycloadditions ; Cycloheptadienones ; Carbocations ; Rearrangements ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of ketenes 1a or 1b with diene 2 in the presence of trifluoromethanesulfonic acid providing the cycloheptadienones 5a and 5b constitutes the first example of an acid-induced ketene/diene «cycloaddition». The thermal [2 + 2] cycloadducts, bicyclo[3.2.0]hept-2-en-6-ones 9, are not intermediates in the acid-catalyzed reaction since they rearrange under acidic conditions to the tetralinone derivatives 10. The acid-catalyzed «cycloaddition» was mechanistically investigated and the scope of the reaction explored.
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    URL: http://dx.doi.org/10.1002/cber.19941270715
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    Coordination Polymers, VI. Neutral 1D-Coordination Polymers from Ethyl (Aminomethylene)cyanoacetate Derivatives and Copper(II) Acetate by Spontaneous Self-Organization (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1283-1286 
    Details
    ISSN: 0009-2940
    Keywords: (Aminomethylene)cyanoacetate, ethyl, derivatives ; Coordination polymers, 1D ; Self-organization, spontaneous ; Copper complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of a solution of copper(II) acetate in methanol with ethyl (aminomethylene)cyanoacetate derivatives 10 (H2L4) or 13 (H2L5) yields the corresponding 1D-coordination polymers 11 ([CuL4]∞ and 14 ([CuL5]∞, respectively. The products are insoluble in non-coordinating solvents and thermally highly stable. The structures of 11 and 14 have been established by X-ray diffraction. The one-dimensional coordination polymers 11 and 14 have different geometries, depending on the lateral group of the ligands.
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    Reactivity of Imines Towards 3-Trifloxypropeniminium and Propyniminium Triflates (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1295-1303 
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    ISSN: 0009-2940
    Keywords: Imines ; Iminium salts ; 3-Trifloxypropeniminium salts ; Propyniminium salts ; Cyclization reactions ; Azacyclobutadiene ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The imines 5 and 11 react with 3-trifloxypropeniminium triflates 1a-d to afford the heterocyclic iminium salts 8, 9, 13, 15, and 17, respectively, or the propeniminium salt 21. Propyniminium triflates 22, 24 react with imines by initial conjugated addition, followed by a reaction sequence analogous to the one observed for the reactions of 1a-d with imines. Thus, salt 22 and aldimine 5b yield the propeniminium salt 21, while 24 reacts with tri-tert-butylazete 25 to afford the semicyclic vinamidinium salt 28. A crystal structure analysis of 28 is performed.
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    URL: http://dx.doi.org/10.1002/cber.19941270719
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    N,N-Bis(trimethylsilyl)ynamines: Cycloaddition Reactions with Dimethyl Acetylenedicarboxylate and Ketenes (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1287-1293 
    Details
    ISSN: 0009-2940
    Keywords: Ynamines, N,N-bis(trimethylsilyl)- ; Cycloaddition reactions ; Cyclopropenes ; Furans ; Ketenes ; Cyclobutenones ; Allenylcarboxamides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N,N-Bis(trimethylsilyl)ynamines 1 react with dimethyl acetylenedicarboxylate (2) in a molar ratio of 1:2 to afford 3-cyclopropenylfurans 3. Configuration and conformation of 3a are confirmed by X-ray crystallography. Addition of a further mol of 1 furnishes the fumarates 4. With ketenes 5 (5c, d are prepared in situ) a competition between the formation of cyclic butenone derivatives 6 and allenic imidates 7 is observed, depending on the substitution pattern of 1. After hydrolytic workup, the corresponding amides 10 or the vinylogous amides 9 are obtained in good yield. These experiments indicate that the silylated ynamines 1 show a completely different, more selective reactivity towards dimethyl acetylenedicarboxylate compared to N,N-dialkyl-substituted ynamines, yielding furan derivatives instead of anilines. Towards ketenes, however, a similar cycloaddition reactivity as for N,N-dialkylynamines is observed.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270718
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    Radikalische Cyclisierung von Dienen, IX. Über die Stereoselektivität der radikalischen 4-exo-trig-Cyclisierung von optisch aktiven (2E)-6-Oxohex-2-ensäureestern mit Samarium(II)-iodid (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1305-1309 
    Details
    ISSN: 0009-2940
    Keywords: Radicals ; Cyclobutanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical-Type Cyclization of Dienes, IX. - On the Stereoselectivity of the Radical 4-exo-trig-Cyclization of Optically Active Ethyl (2E)-6-Oxohex-2-enoates with Samarium(II) IodideEthyl (5R, 2E)-5-(benzyloxy)-4,4-dimethyl-6-oxohex-2-enoate (9) was prepared from (R)-(-)-pantolactone (3) by a series of straightforward reactions. The reaction of 9 with samarium(II) iodide produces enantiomerically pure ethyl (1S,3R,4R)-(-)-[3-(benzyloxy)-4-hydroxy-2,2-dimethylcyclo-butyl]acetate (10) in 60% yield. The absolute configuration at C-1 and C-3 was confirmed by the conversion of 10 to the crystalline 15a, whose absolute configuration is known from its synthesis from (1S,5S)-( + )-α-pinene (12). The configuration of the hydroxy group at C-4 in 10 was determined from NOE studies on the epimiric 17. The radical 4-exo-trig-cyclization of optically active (2E)-6-oxohex-2-enoates with samarium(II) iodide opens a new pathway to enantiomerically pure cyclobutanol and cyclobutanone derivatives, which are of interest as building blocks in natural products synthesis.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19941270720
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    Chiral Organometallic Reagents, XI. Stereoselective Exchange of Diastereotopic Iodine Atoms by Magnesium in 3-Alkoxy-1,1-diiodoalkanes (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1311-1316 
    Details
    ISSN: 0009-2940
    Keywords: 1-Iodoalkylmagnesium reagents ; Stability, configurational ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: α-Iodoalkylmagnesium species were generated by reaction of 3-oxygenated 1,1-diiodoalkanes with isopropylmagnesium halides at -78%C. The resulting magnesium carbenoids were found to be configurationally stable at temperatures up to -20%C and were trapped by benzaldehyde or allyl iodide at low temperatures. Stereoselectivity on exchange of the diastereotopic iodine atoms in 3 was found to be low.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19941270721
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    Stereoselective Synthesis of Alcohols, XLVI. Synthesis of a Hydroxytrioxaadamantane, a Model for the Trioxaadamantane Moiety of Muamvatin (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1317-1322 
    Details
    ISSN: 0009-2940
    Keywords: Cyclization of a hydroxy triketone ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A protected hydroxy triketone 22 has been generated by direct Swern oxidation of a δ-trimethylsilyloxy alcohol 11, avoiding the formation of a δ-hydroxy ketone as an intermediate. Conditions have been worked out, which allow the deprotection of a tert-butyldimethylsilyl group and the spontaneous tricyclization of the resulting hydroxy triketone 4 to an acid-sensitive hydroxytrioxaadamantane 5.
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    URL: http://dx.doi.org/10.1002/cber.19941270722
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    Synthesis and X-Ray Structures of New Macrocyclic Thioethers (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1327-1329 
    Details
    ISSN: 0009-2940
    Keywords: Macrocyclic thioethers ; Adamantane as a building block ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4,6:12,14-Di(1,3-adamantano)-1,9-dithiacyclohexadecane (1), 4,6:12,14:20,22-tri(1,3-adamantano)-1,9,17-trithiacyclotetracosane (2), and 5,7:14,16-di(1,3-adamantano)-1,2,10,11-tetrathiacyclooctadecane (3) have been obtained by intermolecular cyclization of 1,3-bis(2-bromoethyl)adamantane (4) with thioacetamide using a high-dilution technique. The reaction is concentration-dependent. The crystal structures of 1, 2, and 3 have been determined by single-crystal X-ray diffraction.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270724
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    Masthead (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270801
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    (5aS,10aS)-Octahydro-1H,5H-dipyrrolo[1,2-a:1′,2Prime;-d]pyrazin «DPP» als Hilfsreagenz bei der enantioselektiven 1,2-Addition von Grignard-Reagenzien an prochirale Carbonylverbindungen (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1323-1326 
    Details
    ISSN: 0009-2940
    Keywords: Dipyrrolo[1,2a:1′,2′-d]pyrazine, (5aS,10aS)-octahydro-1H,5H- ; 1,2-Addition, enantioselective ; Grignard reagents ; Chiral solvent ; Cryoscopic measurements ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (5aS,10aS)-Octahydro-1H,5H-dipyrrolo[1,2-a:1′,2′-d]pyrazine «DPP» as Auxiliary Reagent for Enantioselective Alkylations of Prochiral Carbonyl CompoundsIn the presence of one equivalent of the title compound «DPP» (1) prochiral carbonyl compounds 2 react with Grignard reagents 3 in THF to form enantioselectively alcohols 4 with up to 98% ee, whereas the addition of one equivalent of triethylamine yields the opposite enantiomers with up to 97% ee. The optimal molar ratio of 1 and magnesium reagent 3 was determined by cryoscopic measurements. Asymmetric induction is supposed to arise from transition states involving monomeric octahedral complexes of Grignard reagent, chiral solvent, and carbonyl compound. DPP (1) also catalyses Grignard alkylations, because a tenth of its stochiometric amount gives an enantiomeric eccess four times more than as expected. Prepared from (S)-proline, only the boat conformation of 1 induces the observed selectivity as detected by 13C-NMR spectroscopy.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270723
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    Borylation of a Stable Primary Enamine (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1331-1332 
    Details
    ISSN: 0009-2940
    Keywords: Primary enamines ; Borylation ; 9-BBN ; Amino-polyene ; Enamines, borylation of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stable conjugated primary enamine 1,6-diamino-1,6-diphenyl-1,3,5-hexatriene (2a) was treated with 9-borabicyclo-[3.3.1]nonane. At 40°C in dichloromethane solution (18 h) only borylation at nitrogen was observed. With loss of dihydrogen a 9-BBN substituent became attached to each enamine nitrogen. The N,N′-diborylated diaminohexatriene product 3 was characterized by X-ray diffraction.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270725
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    Preparation, Properties, and Reactions of Metal-Containing Hetercycles, XC. Reactivity of Differently Activated Alkynes toward Ruthenium and Osmium Complexes of the Type (η2-C2H4)M(CO)4Dedicated to Professor Reinhard Schmutzler on the occasion of his 60th birthday. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1343-1347 
    Details
    ISSN: 0009-2940
    Keywords: Ruthenium compounds ; Osmium compounds ; Alkynes, activated ; Cyclotrimerization ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Depending on the substituents, the reaction of the activated alkynes ZC≡CZ (2a-g) [Z = CO2R: R = Me (a), Et (b); Z = R1: R1 = CF3 (c), CH2Cl (d), CH2Br (e); Z = CH2OC(O)R2: R2 = Me (f), CCl3 (g)] with the labile ruthenium complex (η2-C2H4)Ru(CO)4 (1) results in the formation of three different types of heterocycles. While the reactions of the dialkyl acet-ylenedicarboxylates 2a, b lead to the dimeric tricarbonylru-thenacyclopentadienes 3a, b, being catalytically active in the cyclotrimerization of alkynes like 2a, b, the application of the 1,4-halogeno-2-butynes 2c-e yields the bicyclic heterocycles 4c-e. The esters of 2-butyne-1,4-diol 2f, g are converted into the tetracarbonylruthenacyclopentadienes 5f, g. Investigation of the primary attack of the alkynes 2a-g at complex 1 leads to the conclusion, that an ionic mechanism is preferred in the ruthenium-catalyzed cyclotrimerization of electron-poor alkynes. If, instead of 1, (η2-C2H4)Os(CO)4 (6) is allowed to react with the acetylenes 2a, b the osmium complexes (η4-C6Z6)Os(CO)3 (7a, b) are isolated. In the presence of CO at 2 bar 7a, b release the benzene derivatives C6Z6 (8a, b) with the formation of Os3(CO)12.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270803
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    Wismutverbindungen mit voluminösen, mehrfach alkylierten Cyclopentadienyl-LigandenHerrn Professor Helmut Werner zum 60. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1335-1342 
    Details
    ISSN: 0009-2940
    Keywords: Fulvalenes ; Bismuth complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bismuth Compounds with Crowded Multiply Alkylated Cyclopentadienyl LigandsHerrn Professor Helmut Werner zum 60. Geburtstag gewidmet.Bismuth complexes of alkylated cyclopentadienyl ligands are obtained in good yield on treating bismuth(III) halides with tetraisopropylcyclopentadienylsodium or 1,2,4-tri-tert-butyl-cyclopentadienyllithium. A 1:1 stoichiometric ratio gives the complexes [Cp4iBiCl2] (1), [Cp3tBiCl2] (2), and [Cp4iBiI2] (3) (Cp4i = C5iPr4H, Cp3t = C5H2tBu3-1,2,4). According to X-ray crystal structure analyses, 1 and 3 display dimeric structures with two bridging and two terminal halogeno ligands and η3-coordination of the cyclopentadienyl rings. With half an equivalent of tetraisopropylcyclopentadienylsodium BiCl3 forms [Cp4iBi2Cl5] (4). An X-ray crystal structure analysis of 3 reveals a central Bi2Cl10 core of two edge-sharing BiCl6 octahedra coordinated to two Bi(η5-Cp4i) fragments generating a framework of two face-sharing cubes. Reaction of two equivalents of 1,2,4-tri-tert-butylcyclopentadienyllithium with BiCl3 yields deep purple [Cp3t2BiCl] (5), a bent sandwich complex with an η3,η2-bonding mode of the cyclopentadienyl ligands. Attempted formation of the octaisopropyl analogue of 5 from BiCl3 and two equivalents of tetraisopropylcyclo-pentadienylsodium with elimination of propene gives [Cp4iCp3iBiCl] (6) (Cp3i = C5H2iPr3). Use of monodeuterated tetraisopropylcyclopentadienylsodium in the second substitution step gave pure [Cp4i([D1]Cp3i)BiCl] ([D1]6) proving the absence of ring exchange reactions under the reaction conditions employed and elimination of propene from the second incoming sterically crowded tetraisopropylcyclopentadienyl ring system. The importance of proper choice of solvent and reaction conditions on the formation of alkylated cyclopentadienyl bismuth derivatives is demonstrated by extensive formation of 1,1′,3,3′,5,5′-hexa-tert-butyldihydrofulvalene (7) from 1,2,4-tri-tert-butylcyclopentadienylsodium and BiCl3.
    Additional Material: 8 Ill.
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    Synthesis and Stereochemistry of Chiral Macrocycles Including a 1,2-Bis(phenylphosphanyl)benzene Unit (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1411-1426 
    Details
    ISSN: 0009-2940
    Keywords: 1,1′-Binaphthyls ; Nickel complexes ; Palladium complexes ; Circular dichroism ; Macrocycles, chiral ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the four 1,1′-binaphthyl-based macrocyclic bisphosphane ligands 6b-e (racemic and optically active) and their square-planar cis-P2-MCl2 complexes (M = Ni, Pd) is reported. In three cases isomers could be isolated and identified. The absolute and relative stereochemistry of all ligands and complexes was established on the basis of their NMR and CD spectra and finally confirmed by X-ray structural determinations of selected ligands and complexes.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270815
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    Festkörper-13C-NMR-Spektroskopie, 1. Titantetrachlorid-Komplexe von Diketonen: Ihre Bedeutung für Hydrid-Reduktionen und ihre Festkörper-NMR-SpektrenHerrn Prof. Christoph Rüchardt zum 65. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1427-1436 
    Details
    ISSN: 0009-2940
    Keywords: Asymmetric induction ; TiCl4 complexes ; Solid-state 13C-NMR spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solid-state 13C-NMR Spectroscopy, 1.  -  Titanium Tetrachloride Complexes of Diketones: Their Importance for Hydride Reductions and Their Solid-State NMR SpectraHerrn Prof. Christoph Rüchardt zum 65. Geburtstag gewidmet.The influence of titanium tetrachloride on the diastereoselectivity of hydride reductions of 1,2-, 1,3-, 1,4- and 1,5-diketones has been studied. The effect is especially pronounced in the case of 1,3-diketones, where the addition of titanium tetrachloride reverses the stereoselectivity. The assumption of a chelate of type 32 or 33 can be confirmed by several observations: β-hydroxy ketone 7 and β-benzyloxy ketone 9 show the same dependence on the stereochemical course as diketone 5a. This compound forms complex 34, whose conformation is known by X-ray structure determination. From the solid-state 13C-NMR spectra of the TiCl4 adducts it can be deduced that 7 forms chelate 42, which is close to the assumed intermediate 32. In the case of phenyl-substituted substrates solid-state 13C-NMR spectroscopy can also be used to differentiate between real chelates (coordination of TiCl4 at the oxygen atoms of the carbonyl groups) and π complexes.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270816
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    2,6-Disubstituted 4-Aminopyridines from 1,3-Dialkoxy-2-azapropenylium Salts and N-Methyl-4-piperidone EnaminesDedicated to Prof. D. Dr. Ernst Würthwein on the occasion of his 85th birthday. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1437-1440 
    Details
    ISSN: 0009-2940
    Keywords: 2-Azapropenylium salts, 1,3-dialkoxy- and 1,1,3,3-tetraalkoxy- ; Enamines of N-methyl-4-piperidone ; 4-Aminopyridines ; 3,7-Diazabicyclo[3.3.1]non-2-en-9-ones ; Retro-Mannich reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,3-Dialkoxy-2-azapropenylium salts 1 react with enamines 2 of N-methyl-4-piperidone at room temperature to give 2,6-disubstituted 4-aminopyridines 4, 5 in low to moderate yield after hydrolysis. Intermediates of the reaction of 1a with 2 are the bicyclic iminium salts 6 and 7, which may be detected 1H-NMR spectroscopically prior to hydrolysis. Hydrolysis of the mixture obtained from the reaction of 1a with 2a under basic conditions furnishes the bicyclic ketone 3 as the major product. A “retro-Mannich”-type reaction is suggested to explain the degradation of the bicyclic intermediates 6, 7 with the formation of the pyridines 4, 5.
    Additional Material: 1 Tab.
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    Regio- and Diastereoselective Synthesis of Stannyl Epoxy Alcohols by Direct Hydroxy Epoxidation of Vinylstannanes (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1441-1445 
    Details
    ISSN: 0009-2940
    Keywords: Vinylstannanes ; Photooxygenation ; Schenck reaction ; Hydroxy epoxidation ; Stannyl epoxy alcohols ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The direct synthesis of stannyl epoxy alcohols 3 from vinylstannanes 1 is described. The procedure involves the photooxygenation of Vinylstannanes 1, which proceeds in a highly regioselective manner with predominant hydrogen abstraction geminal to the stannyl group. Subsequent reaction of the resulting hydroperoxides 2 with Ti(OiPr)4 afforded in a one-pot procedure the epoxy alcohols 3 in high diastereomeric excess, which ranged from 81:19 to greater than 95:5. This convenient and effective method was applied to acyclic and cyclic vinylstannanes as well as to γ-trydroxyvinylstannane 1e, which was converted into the stannyl epoxy diol 3e. In this novel hydroxy epoxidation of vinylstannanes the regioselectivity of the singlet oxygen ene reaction (Schenck reaction) is controlled by the stannyl group.
    Additional Material: 1 Tab.
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    Stereoselective Additions of Chiral, Functionalized Organozinc Reagents to Achiral and Chiral Aldehydes: a Matched-Mismatched Case in Organozinc Chemistry (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1447-1457 
    Details
    ISSN: 0009-2940
    Keywords: Addition Stereoselective, nonchelation-controlled ; Reagent, organozinc ; Stereodifferentiation, double ; Oligo(tetrahydrofuran) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The additions of the enantiomerically pure organozinc reagents 17 and 33 to the THF-aldehyde 1 in the presence of the monodentate Lewis acid boron trifluoride - ether give the nonchelation-controlled addition products 7 and 36, respectively (stereoselectivity 95:5, 86:14). These results provide a route to oligo(tetrahydrofuran)s with the relative stereochemistry trans-syn-cis. A stereodirecting effect of the chiral center in the organozinc reagent 17 is found, leading to simple diastereoselectivies in the reaction with achiral aldehydes and to a matched-mismatched case in the reaction with the chiral aldehyde 1.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19941270819
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    Highly Substituted 1,3-Dienes, V. A Theoretical Study of the Stereochemical Effects of tert-Butyl Substituents in 1,3-Butadiene (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1469-1478 
    Details
    ISSN: 0009-2940
    Keywords: Dienes, conjugated ; Conformation ; Butadienes, orthogonal, gauche ; Calculations, ab initio, molecular mechanics ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For 1,3-butadiene and for all mono- and di-tert-butyl derivatives potential energy curves, as function of the C=C-C=C dihedral angle, have been calculated by molecular mechanics methods (MM3). The stereochemical implication of these results are discussed for each of the compounds. The minimum-energy conformer of each derivative has been optimized by ab initio HF calculations, using GAUSSIAN 90 and a 3-21G basis set.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270821
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    Highly Substituted 1,3-Dienes, IV. An Experimental and Theoretical Study of the Stereochemical Properties of 2-tert-Butyl-1,3-butadiene and 2,3-Di-tert-butyl-1,3-butadiene (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1459-1467 
    Details
    ISSN: 0009-2940
    Keywords: Dienes, conjugated ; Conformation ; Butadienes, orthogonal, gauche ; Gas electron diffraction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular structure and conformation of 2-tert-butyl-1,3-butadiene (1) and of 2,3-di-tert-butyl-1,3-butadiene (2) have been studied by the gas electron diffraction method. The monosubstituted compound is observed to have a gauche orientation (ϕ = 32°) of the conjugated C=C bonds. The forces determining the preferred conformation of this molecule (syn or gauche) appear to be similar to those operative in the case of the high-energy conformer of unsubstituted 1,3-butadiene. The disubstituted compound has an approximately perpendicular orientation of the C=C-C=C system (ϕ = 101.5°), and in this case the preferred orientation is described as a result of minimalization of the nonbonded interactions. - Theoretical calculations of the structure and conformation of the two molecules have been carried out by molecular mechanics (MM3) and by ab initio (HF/3-21G) methods. The results from both sets of calculations are in good agreement with the observed structures of the two compounds.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941270820
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    Electronic Structure of Mono- and Bis(carbonyliron) as well as Bis(cyclopentadienyliron) Complexes of 1,4-Dihydro-1,4-diboranaphthalene (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1557-1561 
    Details
    ISSN: 0009-2940
    Keywords: MO calculations, EH ; Iron, tricarbonyl(η6-1,4-dihydro-1,4-diboranaphthalene)- ; Bis(tricarbonyliron) ; Dicarbonyliron-tricarbonyliron ; Bis(cyclopentadienyliron) complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure and bonding of four iron complexes involving the 1,4-dihydro-1,4-diboranaphthalene ligand C8B2H8 (1), namely of the complexes (CO)3Fe(η6-C8B2H8) (2), (μ, η4,η6-C8B2H8)[Fe(CO)3]2 (3), (CO)3Fe(μ,η4,η6-C8B2H8)Fe(CO)2 (4), and of the triple-decker (μ,η6-C8B2H8)[Fe(η5-C5H5)]2 (5), have been investigated by means of the perturbational molecular orbital theory on the basis of the Extended Hückel calculations. Compounds 2 and 3 are 18-VE complexes, whereas 5 is a 30-VE species. The structure of 4 can be best described in terms of a 16-VE complex “Fe(CO)3 heterocycle” and a 18-VE “Fe(CO)2 carbocycle” unit with its iron centers being not directly bond.
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    Chelating Coordination of Di- and Triallylamines: Syntheses and NMR Studies of Trimethylphosphane Nickel and Cobalt ComplexesDedicated to Professor Wolfgang Luettke on the occasion of his 75th birthday. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1563-1568 
    Details
    ISSN: 0009-2940
    Keywords: Allylamine nickel complexes ; Allylamine cobalt complexes ; 2D NMR, TOCSY ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 16-Electron complexes of zerovalent nickel with diallylamines, Ni[(C3H5)2NR]L [1, 2: L = P(CH3)3, R = CH3, C6H5; 3: L = P(C6H5)3, R = CH3] and [NiP(CH3)3]2CH2[N(C3H5)2]2 (4), were synthesized by reduction of NiCl2L2 with magnesium in tetrahydrofuran. NiCl(η3-C3H5)[P(CH3)3]2 (5), a low-yield byproduct, was also obtained in high yield from NiL4 and C3H5Cl. With triallylamine as starting material complexes Ni[(C3H5)3N]L [6: L = P(CH3)3; 7: L = P(C6H5)3] were generated exhibiting η6- and η4-olefin coordination, respectively. 17-electron cobalt(O) compounds Co[(C3H5)2NR](PMe3)2 (8, 9: R = CH3, C6H5) were obtained by reaction of Co(cyclo-C5H8)(PMe3)3 with the corresponding diallylamine, while CoR(PMe3)4 (R = CH3, C6H5) reacted with N,N-diallylaniline to give diagmagnetic Co[(η3-C3H4)(η2-C3H5)NC6H5](PMe3)2, (10). The coordination mode of allylic functions was deduced from IR, ESR and especially 1H- and 13C-NMR spectra including 2D-NMR experiments.
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    URL: http://dx.doi.org/10.1002/cber.19941270903
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    Thermisch kontrollierte oxidative Lineartrimerisierung von Alkinylgruppen in (Trimethylphosphan)nickel-Komplexen: Strukturen und die Rolle ligandreicher Vorstufen NiX(C≡CR)PMe3)n (n = 2-4) (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1569-1578 
    Details
    ISSN: 0009-2940
    Keywords: Alkynylnickel halides ; Nickel complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidative Linear Trimerization of Alkynyl Groups in (Trimethylphosphane)nickel Complexes: Structures and the Role of Ligand-Rich Precursors NiX(C≡CR)(PMe3)n (n = 2-4)Oxidative additions of 1-halogenoalkynes XC≡CR; to Ni(PMe3)4 afford high yields of pentacoordinate ionic alkynylnickel compounds [Ni(C≡CR)(PMe3)4]+X- [R = SiMe3, X = I (1); R = CMe3, X = I (2), Br (3); R = SiEt3, X = I (6), Br (7); R = SiiPr3, X = I (10), Br (11), R = Ph, X = I (21), Br (22)] or complex molecules Ni(C≡CR)X(PMe3)3 [R = SiPh3, X = I (14), Br (15); R = Ph, X = I (19), Br (20)]. Dissociation of trimethylphosphane gives square planar trans-Ni(C≡CR)X-(PMe3)2 [R = CMe3, X = Br (4), Cl (5); R = SiEt3, X = Br (8), Cl (9); R = SiiPr3, X = Br (12), Cl (13); R = SiPh3, X = I (16), Br (17), Cl (18); R = Ph, X = I (23), Br (24), Cl (25)] but with R = SiR'3, X = I the title reaction dominates with formation of trans-Ni[C(C≡CR)=CR(C≡CR)]I(PMe3)2 [R = CMe3 (26), SiEt3 (29), SiiPr3 (32)]. Thermal activation is necessary in order to obtain trans-Ni[C≡CR)=CR(C≡CR)]X(PMe3)2 [R = CMe3, X = Br (27), Cl (28); R = SiEt3, X = Br (30), Cl (31); R = SiiPr3, X = Br (33), Cl (34)], while only thermal decomposition is observed with trans-Ni(C≡CR)X(PMe3)2 (R = Ph, SiPh3). Examples for both types of reactivity including structural data are given: trans-Ni(C≡CRSiMe3)Br(PMe3)2 and 25 crystallize in the space group P1. Pentacoordinate 19 (space group P21) adopts a trigonal pipyramid of ligand donor atoms with equatorial phenylethynyl and iodo ligands.
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    Umsetzung einiger Dihydrobenzoxazaphosphorinone mit Nucleophilen; ungewöhnliche Oxidations-, Insertions- und Umlagerungsprodukte und deren Charakterisierung durch Einkristall-Röntgenstrukturanalyse (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1579-1586 
    Details
    ISSN: 0009-2940
    Keywords: Benzoxazaphosphorinones ; Rearrangements ; Ring-expansion reaction ; Insertion reaction ; Gold complex ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of some Dihydrobenzoxazaphosphorinones with Nucleophiles; Unusual Oxidation, Insertion, and Rearrangement Products and their Characterisation by Single-Crystal X-Ray AnalysisThe reaction of 2-chloro-1,2-dihydro-1-methyl-4H-3,1,2-oxazaphosphorin-4-one (2) and its 2-diethylamino-substituted derivative 3 with various nucleophiles yielded novel and sometimes unexpected products. Hydrolysis of 2 furnished the 2-hydroxybenzoxazaphosphorinone 4. In the presence of small amounts of water, two molecules of 4 were transformed into 5, accompanied by cleavage of one of the heterocyclic rings. The reaction of 2 with sodium chlorodifluoroacetate led, possibly in an Arbuzov-type reaction, to compound 6. The 1,5-diaza-4,8-cyclooctanedione system 7 was formed by reaction of 2 with 1,2,4,5-tetrakis(trimethylsilyloxy)benzene with concomitant loss of the phosphorus-containing group. 2,2′-Bis(trimethylsiloxy)biphenyl reacted with 2 in the expected fashion to form the diphosphorus compound 8. From 8 the chlorogold(I) complex 9 was obtained. The reaction of 3 with tetrachloro- and tetrabromo-o-benzoquinone did not lead to the expected spirocyclic products by oxidative addition of the quinone system to λ3P. Instead, cleavage and expansion of the heterocyclic ring system with formation of the tricyclic derivatives 10 and 11 took place. Compounds 5-10 were subjected to X-ray structure analysis. Compound 5 exists as two modifications 5a and 5b, which differ mainly in the relative orientation of the phenyl rings; intramolecular N-H…O hydrogen bonds are observed. Bond lengths at the halo-substituted carbon atom in 6 indicate steric crowding. The central 8-membered ring of 7 displays a “tub” conformation. Compound 8 undergoes a conformational change on complexation to the two gold(I) centres; one of the torsion angles C-O(exocyc.)-P-N is -163° in 8, but 95° in 9. The structure determination of 10 served only to confirm the (unexpected) connectivity; the crystal quality was too poor to allow quantitative conclusions.
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    Umsetzung von Isothiocyanaten und Isonitrilen mit R2Al-AlR2 [R = CH(SiMe3)2]; ein- und zweifache Insertion von Isonitril in die Aluminium-Aluminium-Bindung (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1587-1592 
    Details
    ISSN: 0009-2940
    Keywords: Al-Al bond ; insertion of isonitriles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of Isothiocyanates and Isonitriles with R2Al-AlR2 [R = CH(SiMe3)2]; Single and Double Insertion of Isonitrile into the Al-Al BondTetrakis[bis(trimethylsilyl)methyl]dialuminium(4) 1 reacts with phenyl or tert-butyl isothiocyanate with cleavage of the C = S double bond. Two compounds are formed: R2Al-S-AlR2 [R = CH(SiMe3)2] 3 and R2Al-C(NR')-AlR2 (4 R' = C6H5; 5 R'= CMe3) with a sulfur atom or an isonitrile group inserted between the aluminium atoms. Compounds 4 and 5 were isolated in high yield by the reaction of 1 with the appropriate isonitriles. By using an excess of phenyl isonitrile a dark red compound 6 is obtained with two isonitrile units inserted into the Al-Al bond and formation of a C-C single bond. According to crystal structure determinations of 4 and 6 a three-membered heterocycle is formed by the interaction of the nitrogen lone-pair to one of the Al atoms in 4, while in 6 both Al atoms are four-coordinated by bonding to a nitrogen and a carbon atom with formation of two across the C-C bond anellated four-membered heterocycles. As shown by NMR spectroscopy the molecular structure of 4 with one stereochemically saturated and one unsaturated Al atom is unchanged in solution even upon heating to 100°C.
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    URL: http://dx.doi.org/10.1002/cber.19941270906
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    Phosphonium Ylides with Functionalized Silyl Substituents (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1599-1603 
    Details
    ISSN: 0009-2940
    Keywords: Silicon compounds ; Ylides ; NMR, 13C, 17O, 29Si ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two series of aminophosphonium ylides with reactive alkoxychlorosilyl substituents (R2N)3P=CHSi(OR')2Cl (1-8, R = Me, Et/R' = Me, Et, iPr, tBu) have been prepared by reaction of the aminophosphonium ylides (R2N)3P = CH2 with the corresponding dialkoxydichlorosilanes Cl2Si(OR')2. Substituent effects have been investigated by heteronuclear solution NMR studies of the nuclei 1H, 13C, 15N, 17O, 29Si, and 31P. These studies show an alternating shielding effect along the C-O-Si-C backbone. Further reactions of the chlorosilylated ylides with the aminomethylenephosphorane (Me2N)3P=CH2 lead to the formation of the bis-ylidic compounds [(Me2N)3P=CH]2Si(OR')2 (9, 10), which are also available in one-pot syntheses. The molecular structure of [(Me2N)3P=CH]2Si(OiPr)2 (9) has been confirmed by single-crystal X-ray diffraction. In the crystal the molecules have two ylidic carbon centers with planar configuration, which are bridged by a nearly tetrahedral silicon atom. Short P-C and Si-C distances indicate a stabilizing effect of the carbanionic centers.
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    Pyridinio-isoalloxazinophanes as Model Systems for Active-Site Complexes in Flavoenzymes: Syntheses, X-Ray Structure Analyses and Spectroscopic Properties (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1667-1680 
    Details
    ISSN: 0009-2940
    Keywords: Isoalloxazinocyclophanes ; Pyridinio-isoalloxazinophanes ; Nicotinic ester and nicotinic acid isoalloxazinophanes, intramolecular interactions of, X-ray structure analyses of ; Flavin-nicotinamide models ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As model systems for active site complexes in flavoenzymes, flavin and nicotinamide analogues were linked together in cyclophane skeletons of specific sterical structures. Elaborating this concept, we prepared [4]metacyclo[3](10,6)isoalloxazinophane (3), [4](3,1)pyridino[3](10,6)isoalloxazinophane (4), as well as the 16-methoxycarbonyl and the 16-carboxylato derivatives (2 and 34, resp.), of 4 by multistep syntheses. For the isoalloxazinophanes 2, 3, 4, and 34 X-ray structure analyses were performed and are discussed with regard to intramolecular interactions. Preliminary UV/Vis-spectroscopic results related to π…π interactions in these isoalloxazinophanes are reported.
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    URL: http://dx.doi.org/10.1002/cber.19941270918
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    Synthesis and Characterization of Nitrido(tetra-tert-butylphthalocyaninato)- rhenium(V) and Nitrido(phthalocyaninato)rhenium(V) (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1681-1685 
    Details
    ISSN: 0009-2940
    Keywords: Rhenium(V), nitrido(tetra-tert-butylphthalocyaninato)- ; Rhenium(V), nitrido(phthalocyaninato)- ; Phthalocyaninato complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4-tert-Butylphthalodinitrile (1) reacts with ammonium perrhenate, NH4ReO4, to yield nitrido(tetra-tert-butylphthalocyaninato)rhenium(V), (tBu)4PcReN (2), which is characterized by IR, UV/Vis, CV, MS, 1H and 13C NMR, and elemental analysis. It shows good solubility in common organic solvents. In solution 2 is assumed to be monomeric whereas in the solid state also dimers or higher aggregates are present. From the NMR spectra it is concluded that different constitutional isomers of 2 are formed but not in the expected ratio of a statistical distribution. By analogy with 2, the already known nitrido(phthalocyaninato)rhenium(V), PcReN (3), is prepared for comparison.
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    Aminoglycoside Antibiotics  -  Modified, Enantiopure Sannamine- and Sporamine-Type Glycosyl Acceptors (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1687-1697 
    Details
    ISSN: 0009-2940
    Keywords: Sannamines ; Sporamines ; Glycosyl acceptors, 4-epimers, fluorinated, enantiopure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Along an established scheme, 1,2:3,4-dianhydrodeoxy-epi-inositol (3)  -  readily available from benzene  -  has been applied to expeditious syntheses of suitably protected, fluorinated, and epimerized aminoglycoside building blocks related to sannamine (rac-14a, rac-16a, rac-18a, rac-31a) and sporamine (rac-21a, rac-23a, rac-26a, rac-34a). By separation of diastereomers formed with (+)-(1-phenylethyl)amine (14c/ 14′c; 16c/16'c) or with (-)-camphanic acid (14e/14'e) and by enzymatic hydrolysis (rac-14b) access is gained to enantiopure glycosyl acceptors.
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    Enantioselective Synthesis of Polyfunctional Small Building Blocks with a Quaternary Stereogenic Center (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1707-1721 
    Details
    ISSN: 0009-2940
    Keywords: Asymmetric synthesis ; SAMP,RAMP-Hydrazones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Application of the SAMP-/RAMP-hydrazone method offers an efficient and flexible access to compounds with a quaternary stereogenic center. Examples bearing silyl, thio, phenyl, aldo, keto, ester, and alkyl functionalities are described. The 2-phenylaldehydes and -ketones and the β-keto esters 4 were obtained in good overall yields and with variable enantiomeric excesses. The synthesis of the thiolated 2-formyl and 3-formyl carboxylic esters 12 was achieved in high overall yields and with high enantiomeric excesses. The silylated carboxylic ester and acids 16 were produced in moderate to high overall yields and with moderate to excellent enantiomeric excesses, depending on the electrophile used for the quaternization. The absolute configurations of the compounds 12 and 16 were determined by X-ray structure analyses, and the mechanism of the quaternization is postulated.
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    Synthese von N-acylierten 5,10-Dihydrophenazin-Verbindungen (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1723-1728 
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    ISSN: 0009-2940
    Keywords: Phenazines, 5,10-dihydro- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of N-Acylated Derivatives of 5,10-DihydrophenazineA family of N-mono- and N, N'-diacylated 5,10-dihydrophenazines (4-26) was prepared by reaction of 5, 10-dihydrophenazine (1) or the corresponding 5,10-bis(trimethylsilyl) derivative (3) with acyl chlorides. 5,10-Bis(4-nitrobenzoyl)-5,10-di-hydrophenazine (11) was hydrogenated to the new aromatic diamine 21 which is an interesting starting material for polymer syntheses.
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    URL: http://dx.doi.org/10.1002/cber.19941270923
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    Dimere Bis(trialkylphosphan)rhodiumchloride: Darstellung und Charakterisierung (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1927-1929 
    Details
    ISSN: 0009-2940
    Keywords: Rhodium(I) complexes ; Trialkylphosphane complexes ; Dimerization equilibrium ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dimeric Bis(trialkylphosphane)rhodium Chlorides: Preparation and CharacterizationHigh-yield methods for the preparation of (PMe3)3RhCl (2) and [(R3P)2RhCl]2 [R = Me (3a); iPr (3b), and cyclohexyl (3c)] are described. The dimeric nature of 3b in the solid state has been established by an X-ray analysis.
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    Hetero-ansa-Bridged Main Group Metallocenes  -  a Structural and NMR Study (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1901-1908 
    Details
    ISSN: 0009-2940
    Keywords: Diborane(4) dianion, 1,2-bis(dimethylamino)-1,2-di-9-fluorenyl- ; Li, Na, K, Cs salts ; Ca, Ba salts ; Main group metallocenes ; Hetero-ansa-bridged metallocenes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,2-Bis(dimethylamino)-1,2-di-9-fluorenyldiborane(4) (1) is doubly metallated with group 1 and 2 metals to yield metal 1,2-bis(dimethylamino)-1,2-di-9-fluorenyldiborate(4) 2-Li to 2-Ba. The conformations of these compounds in solution are investigated by NMR spectroscopy, and the solid-state structures of 2-Li · 5 THF, 2-K · 4 THF, 2-K · 2 DME, and 2-Ca · 2 THF are determined by X-ray diffraction. All four structures can be described as main group metallocenes. The potassium derivatives form contact ion pairs, leading to polymeric chain-like structures. In contrast, 2-Li · 5 THF exhibits the rare combination of a contact ion pair with a solventseparated ion pair, giving the monomeric structure [Li(THF)4][(fl2B2(NMe2)2)Li · THF]. 2-Ca · 2 THF, which is also monomeric, adapts a severely distorted geometry.
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    Reactions of Monomeric Phosphanylboranes with Acyl Chlorides: 1-Oxa-3-oxonia-5-phospha-2-borata-3,5-cyclohexadienes (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1923-1926 
    Details
    ISSN: 0009-2940
    Keywords: 1-Oxa-3-oxonia-5λD3-phospha-2-boratacyclohexadiene derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monomeric B-[bis(trimethylsilyl)phosphanyl]-9-borabicyclo-[3.3.1]nonane (1) reacts with acyl chlorides 2 in a 1:2 ratio to afford deep red derivatives of six-membered oxaoxonia-s̰2,λD3-phosphaboratacyclohexadienes 3. In contrast, the (di-tert-butylboryloxy)phosphaethene 5 is obtained from tBu2BP-(SiMe3)2 (4) and PhC(O)Cl. It is assumed that both reactions proceed via a common intermediate, an (acylphosphanyl)bo-rane 6. The color of compounds 3, which feature a flat boat conformation, is due to a π-π* transition.
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    Reactions and Structure of Electron-Precise Triborane(5) and Tetraborane(6) Derivatives (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1909-1922 
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    ISSN: 0009-2940
    Keywords: Triboranes(5), 1,ω-disubstituted ; Tetraboranes(6), 1,ω-disubstituted ; Hexaborane(8), octakis(dimethylamino)- ; Electron-precise polyboranes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An improved synthesis of B3(NMe2)5 (2), B4(NMe2)6 (1), and B6(NMe2)8 (4) is reported. From each compound two of the four terminal dimethylamino groups are readily replaced by halogen atoms yielding α,ω-dihalides Bn(NMe2)nX2 (n = 3, 4; X = Cl, Br, I). These are used in turn to replace the substitu-ent X by groups like RO, RS, RHN, R2P, and R. Crystal structure determinations on several of these compounds reveal as a common feature planar (C2N)BB2 and (C2N)B(B)X groups which are arranged in an approximately orthogonal manner to one-another with NBBN dihedral angles ranging from 69 to 104.6°. Consequently, there is no significant π bonding between the boron atoms.
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    URL: http://dx.doi.org/10.1002/cber.19941271015
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    [2,3]-Thia-Wittig Rearrangements of α-Lithiated Sulfides Via De-aromatized Cyclohexadiene Intermediates Proceed with Inversion of Configuration at the Carbanionic Center (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1949-1957 
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    ISSN: 0009-2940
    Keywords: Stannanes, α-(alkylthio) ; Wittig rearrangement ; Configurational stability ; α-Lithio sulfides ; [2,3] Rearrangement ; Stereoselectivity ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nBuLi-induced tin/lithium exchange reactions of the di-astereomeric γ-[(methoxyethoxy)methoxy]-]α-(tributylstannyl) sulfides anti- and syn-8 delivered the α-(lithioalkyl) benzyl sulfides anti- and syn-11, respectively. Within 1 h at -78°C, these species underwent [2,3]-thia-Wittig rearrangements in THF via the de-aromatized cyclohexadiene intermediates syn- and anti-12. Tautomerization and protonation yielded 81:19 (85%) and 19:81 mixtures (96%) of the ortho-functionalized toluenes syn- and anti-13. Probably, both Wittig rearrangements proceeded with 100% inversion of configuration at the carbanionic stereocenter, and the overall loss of stereoselectivity is due to an epimerization anti-11 ⇌ syn-11 of the lithio sulfide intermediates at a rate which is 3.3 times slower than the rearrangement.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941271019
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    (R)-1,2,2-Triphenyl-2-(trimethylsiloxy)ethyl Propionate: anti-Selective and Diastereofacially Selective Aldol Addition; Diastereoselective Silylation and Alkylation (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1959-1968 
    Details
    ISSN: 0009-2940
    Keywords: Aldol reaction ; Chiral etiolate ; Mandelic acid ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The propionates (R)-5 and (R)-6 which are derived from the readily available chiral auxiliary reagent (R)-triphenylglycol (4) have been applied in stereoselective aldol reactions. Whereas the enolate 7 and the silyl ketene acetal 12, both generated from the ester (R)-6, display only moderate diastereoselectivity when treated with benzaldehyde, ß-hydroxyesters 8b and 16a, b are formed in diastereomeric ratios up to 95:5 (ratio of the main product to the sum of all other stereoisomers) when the propionate (R)-5 is subsequently deprotonated, transmetalated into the zirconium enolate and allowed to react with aldehydes. Alkaline hydrolysis or reduction with LiAlH4 enables the conversion of the adducts 8a and 16a
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941271020
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    Synthesis and Reactions of 7-Oxonorbornane-2,3-dicarboximides (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1933-1947 
    Details
    ISSN: 0009-2940
    Keywords: 7-Oxonorbornane-2,3-dicarboximides ; Reductive amination ; 4,7-Methanoisoindoles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ozonizations of several 7-isopropylidenenorbornane-2,3-dicarboximides (2, 10) yield 7,7-dihydroxynorbornane-2,3-dicarboximides (3, 11) and/or 7-oxonorbornane-2,3-dicarboxi-mides (4, 12). Dehydration of the dihydroxy derivatives to the corresponding carbonyl compounds can be carried out by reaction with P2O5 in an aprotic solvent. Reaction of hydrates 3 with methanol gives mixtures of the stereoisomeric hemiacetals 13 and 14, whereas reaction with other nucleophiles give only the stereoisomer derived from attack by the less hindered carbonyl face. Thus NaBH4 or Al(iPRO)3 reduction of 3 or 4 yields alcohols 15 and LiAlH4 reduction of 3 or 4 amino alcohols 16. Reaction of 4b with phenylmagnesium bromide gives alcohol 22 and a direaction product (rac-26) that easily dehydrates to a tetracyclic compound (rac-30). Reductive aminations of 3 or 4 lead to amines 19 directly or via imines rac-20 and amines 23. LiAIH4 reduction of amine 23b affords tricyclic compounds (rac-27) and (rac-28). The last one was converted to diamine 24 by reduction with NaBH3CN. Similarly, amine 21 was converted into diamine 25, partially via aminal 29 as intermediate. The structures of compounds 3b, 19a, rac-27, and rac-30 have been established by X-ray diffraction analysis.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941271018
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    Enantioselektive Protonierung von Lacton-EnolatenHerrn Professor Helmut Werner zum 60. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1969-1980 
    Details
    ISSN: 0009-2940
    Keywords: Protonation ; Enantioselectivity ; Lactone enolates ; Chiral proton sources ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoselective Protonation of Carbanions, 4[1].  -  Enantioselective Protonation of Lactone Enolates[2]The prochiral lithium enolates derived from the five-membered lactones rac-1 and rac-2 were protonated by 37 OH-and 21 NH-chiral proton sources in THF at  -  78°C. The enantioselectivities, determined directly from the reaction mixture by chiral HPLC, are always higher for system 1, probably due to restricted rotation of the phenyl group in 1Li at low temperature (NMR) and range from 0-54% ee. The strongest stereodifferentiation is observed if the OH or NH acids carry an adjacent O- or N-containing group (structures G-J) which allows complexation with the lithium ion. A plausible transition state involving the dimeric lithium enolate is proposed.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941271021
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    Hexakis(alkylthio)-Substituted Unsymmetrical Phthalocyanines (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2009-2012 
    Details
    ISSN: 0009-2940
    Keywords: Phthalocyanines, unsymmetrical, soluble ; Boron complex ; Phthalonitrile derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclotrimerization of 4,5-bis(hexylthio)phthalodinitrile (1) in 1-chloronaphthalene in the presence of BCl3 leads to the subphthalocyanine 4. Unsymmetrical phthalocyanines (5, 6) with six alkylthio substituents on three of the benzenoid units are synthesized by the reaction of 4 with an diiminoisoindoline derivative (R′ = H or NO2). These extremely soluble compounds are characterized by IR, 1H- and 13C-NMR as well as UV/Vis spectra.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941271025
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    Enantioselektive Protonierung von γ-Butyrolacton-EnolatenHerrn Professor Wolfgang Lüttke zum 75. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1989-1992 
    Details
    ISSN: 0009-2940
    Keywords: Enantioselectivity ; Protonation ; Ester enolates ; Lactones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoselective Protonation of Carbanions, 6[1].  -  Enantioselective Protonation of γ-Butyrolactone Enolates*The lithium enolates 3Li-7Li, produced from 3-7 by LDA or LiHMDS in THF, are protonated with eleven chiral proton sources at -78°C in THF which produced high enantioselectivities with 1Li and 2Li[5]. Although the enolates (3Li, 6Li, 7Li) are not deuterated quantitatively[1], 1H- and 13C-NMR spectra in THF at -78°C reveal not only quantitative deprotonation (3Li, 6Li) but also aggregation (dimerisation) and hindered rotation of the phenyl group in 3Li. From comparison of the enantioselectivities produced by five chiral proton sources with 1Li-6Li (Tab. 4) definite structure/selectivity correlations can not be derived both for the enolates and the proton sources.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941271023
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    Einfluß der Reaktionsbedingungen auf die enantioselektive Protonierung von Lacton-EnolatenProfessor Helmut Quast zum 60. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1981-1988 
    Details
    ISSN: 0009-2940
    Keywords: Enantioselectivity ; Protonation ; Solvent effects ; Lewis acids ; Lithium salts ; Deuteration ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoselective Protonation of Carbanions, 5[1].  -  Effects of Reaction Conditions on the Enantioselective Protonation of Lactone Enolates[2]Protonation of the enolates 1Li and 2Li by using standard conditions yields enantioselectivities up to 54 and 50% ee, respectively, depending on the chiral proton source[1]. These values may change dramatically by the following variations (standard ee's in parenthesis): (i) In Et2O/THF (90:10) (S)-2 with 72% ee (44%) is formed with (R)-pantolactone (3) but only 48% ee (39%) with (R,R)-tartaric ester 4 (Figure 1). (ii) Lewis acids may produce rac-2 (SnCl2, MgBr2) or definitely increase the enantioselectivity: With lactone 3: 46% ee (44%); with esters 4: 48% ee (39%); with bissulfonamide 7: 67% ee (47%) (Table 1, 2). (iii) Lithium chloride (2-4 equiv.) in THF yields (S)-1 with 68% ee (47%) and (S)-2 with 77% ee (39%) but only if ester 4 ist employed as chiral proton source (Figure 2). (iv) Chiral Lewis bases create (S)-2 with up to 30% ee on protonation with achiral acids (Table 3, 4). (v) Deuteration of 2Li ranges from 16 to 95% depending on the nature of the base as well as the deuteron source. The degrees of deuteration and enantioselectivity are not correlated. All results demonstrate the complexity of enantioselective protonation of enolates which still needs empirical optimization.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941271022
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    Oligooxa[3n.3]paracyclophane Quinhydrones  -  Cation-Induced Charge-Transfer Absorptions and Structures of the Metal Complexes (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1993-2008 
    Details
    ISSN: 0009-2940
    Keywords: Electron donor-acceptor cyclophanes ; Charge-transfer compounds ; Crown ethers ; Oligooxaparacyclophane metal complexes, charge-transfer absorption of, crystal structures of ; Cyclophanes, electron donor-acceptor ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The intramolecular oligooxa[3n.3]paracyclophane quinhy-drones 2-5 (with n = 3 to 6) were synthesized and their interactions with alkali and alkaline earth metal and mercury(II) ions were studied by electron absorption and NMR spectroscopy. Remarkable enhancements of the CT absorptions were observed by complexation with metal ions of the pentaoxa[15.3]paracyclophane quinhydrone 4 and the hexaoxa[18.3]paracyclophane quinhydrone 5 to the corresponding complexes 6a-e and 7, respectively. The various donor-acceptor orientations and the crown ether-like complexation in the calcium complex 6d, the mercury complex 6e and the barium complex 7 were determined by X-ray analysis. Moreover, the X-ray structures of the tetramethoxy-2,5,8-trioxa[9.3]paracyclophane 8a, a precursor of the quinhydrone 2, and of the pentaoxa[15.3](2,5)-p-benzoquinonophane 20, the product of oxidative demethylation of the quinhydrone 4, are given. For comparison with the cyclic quinhydrones acyclic analogs are also described.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941271024
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    Neue Synthesen von Methyleniminium-Salzen aus Carbonylverbindungen und aus α-Chlorethern; ein Zugang zu vinylogen Viehe-Salzen* (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2013-2022 
    Details
    ISSN: 0009-2940
    Keywords: Methyleniminium salts, preparation, mechanisms of formation ; (Dialkylamino)trimethylsilanes ; Ethers, α-chloro ; Viehe salts, vinylogous ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Syntheses of Methyleniminium Salts from Carbonyl Compounds and from α-Chloro Ethers; an Access to Vinylogous Viehe Salts*Two methods for the synthesis of isolable methyleniminium salts and amidinium salts are presented. In the first case carbonyl compounds A are treated with a mixture of (dialkyl-amino)trimethylsilane (12) and chlorotrimethylsilane (13) or 12 and trimethylsilyl triflate (14) leading to the iminium chlorides F or iminium triflates G, respectively. With 12/13 the preparation of F is limited to non-enolizable aldehydes and dimethylformamide (10), while 12/14 enables the preparation of G, e.g. 23a-25a, 27a, also with ketones and with substituted amides. The second procedure is based on the treatment of α-chloro ethers L with 12. Both methods afford the Mannich reagent 16a in high yields. By reaction of the α-chloro ether 35 with 12 in diethyl ether the vinylogous Viehe salts 36a-c, e become available for the first time. The reaction pathways are discussed.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941271026
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    Dithiacyclooctine (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2035-2041 
    Details
    ISSN: 0009-2940
    Keywords: Alkynes ; Cycloalkynes ; Strain, steric ; Cycloaddition reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enthalpies of formation ΔHf and the ring strain energies Eg were calculated for the nine isomeric dithiacyclooctynes 1--9 by applying the MNDO method. Reaction Scheme 2 shows the synthesis of 1,4-dithia-2-cyclooctyne (1), which was the highest Eg value in this series. It dimerizes to 13 in the absence of reaction partners. Scheme 4 summarizes the preparation of 1,5-dithia-2-cyclooctyne (2) and its homologue 1,5-dithia-2-cyclononyne (23) and Scheme 6 the preparation of 1,4-dithia-6-cyclooctyne (6) and its homologue 1,5-dithia-7-cyclononyne (29). Depending on the position of the sulfur atoms, all three reaction sequences contain different steps for the introduction of the triple bonds.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19941271028
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    Diastereoselective Synthesis of α-Hydroxy- and α-Aminoindolizidines and -quinolizidines. Evidence for a Novel Cyclization/Hydride Migration Mechanism in the TiCl4-Induced Reaction of Prolinal Benzylimines by Deuterium Labeling Studies (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2023-2034 
    Details
    ISSN: 0009-2940
    Keywords: Imines ; Indolizidines ; Quinolizidines ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lewis acid-catalyzed cyclization of prolinal and 2-piperidine-carbaldehyde benzylimines 11, 12 results in the diastereoselective formation of α-amino-β-alkyl-substituted indolizidines 15, 17, 19, 21 and -quinolizidines 16, 18, 20, respectively. Both diastereoselectivity and constitution depend on the Lewis acid. FeCl3 yields α,β-trans-α-(benzylamino)-β-isopropenyl derivatives 15 and 16, probably by a cationic cyclization via carbenium ions 32a, b. In contrast, TiCl4 yields α,β-cis-α-(benzylideneamino)-β-isopropyl derivatives 19 and 20 by a novel cyclization/intermolecular hydride transfer mechanism, which was supported by deuterium labeling studies. Compounds 15, 16, 19, and 20 were converted to the diastereomeric acetamides 24, 25 and 28, 29. By an analogous cyclization of the aldehydes 8 and 9 only α,β-cis-α-hydroxy-β-isopropenylindolizidines 51 and -quinolizidines 52 were obtained irrespective of the Lewis acid used. The structures of 30 and 52 were elucidated by X-ray analysis.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941271027
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    Graphical Abstract (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. A-121 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941271036
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    A Chiral Adamantanophane: Preparation, Enantiomer Separation, Theoretical and Experimental Circular Dichroism and Absolute Configuration (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2081-2088 
    Details
    ISSN: 0009-2940
    Keywords: Adamantanophanes ; Calculations, CI ; Circular dichroism ; Cyclophanes ; Strain energy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Exchange of aromatic units (e.g. benzene) for aliphatic/ali-cyclic building blocks (e.g. adamantane) in cyclophanes leads to molecules of the “araliphane” type. The synthesis of the highly strained [2.2](1,3)adamantanometacyclophanes 5a-c is described. The cyclophane skeletons of these molecules are conformationally rigid and therefore 5a-c are planar-chiral. The circular dichroism of 5c has been calculated theoretically with NDDO/MRD-CI methods and was measured. Agreement of theory and experiment is good, a comparison of both allows the assignment of the absolute configuration of the two enantiomers of 5c with high probability. Furthermore, analysis of the nπ* band in the CD spectrum yields a, simple general rule to determine the conformation of the carboxyl group in phenyl ester substructures. Theoretical calculations of the strain energy (Es) of 5c reveal the distribution of strain within the molecule.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941271034
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    Masthead (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941271201
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    Ein neues, Deltaphan und bandförmige Cyclophane (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2089-2096 
    Details
    ISSN: 0009-2940
    Keywords: Aza-phanes ; Cyclophanes ; Molecular belts ; Macrocycles ; CH-π interaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A New Deltaphane and Ribbon-Shaped CyclophanesThe reaction of the fourfold functionalized [3.3][3.3]metacyclophane 8 with tosylamide monosodium salt leads to a new deltaphane in quantitative yield. An X-ray analysis confirms the belt-shaped structure of 3. Moreover, a series 10-15 of well-soluble belt-shaped macrocycles with up to 21 interconnected benzene rings were detected. The intermediate [3.3][3.3]metacyclophane 4 shows remarkably short distances to enclosed toluene, one toluene molecule acting twice as a π acceptor and once as a π donor. Competition experiments with benzene demonstrate the dependence of conformational behaviour on the solvent.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19941271035
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    Chelat-kontrollierte diastereoselektive Addition an α,ß-Epoxy-Aldehyde (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 905-909 
    Details
    ISSN: 0009-2940
    Keywords: Allyltributylstannane ; Trimethylsilyl cyanide ; α,β-Epoxy aldehydes ; Chelation-controlled addition ; Diastereoselectivity ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chelate-Controlled Diastereoselective Addition to α,β-Epoxy AldehydesLiClO4-mediated reaction of trans-substituted α,β-epoxy aldehydes 1 with allyltributyltin (2) or trimethylsilyl cyanide provides a general method for the synthesis of the corresponding syn-alcohols 3 with high selectivity. In the case of cis-substituted α,β-epoxy aldehydes the selectivity depends on the size of the substituents.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19941270519
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