摘要:

AbstractNovel lipophilic γ‐amino acids8and9analogous to GABA containing cyclopropane rings are synthesized by Rh(II)‐catalyzed reaction of diazo compounds2and3withN,N‐bis(trimethylsilyl)allylamine(1)and subsequent hydrolysis. In addition, routes are described leading to the vinylogous GABA analogue15and to the unusual tricyclic γ‐ami

ISSN:0941-1216    

DOI:10.1002/prac.19953370112

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

AbstractRelative autoxidation rates were determined for the cycloalkanes C7to C12, the methyl cycloalkanes C6to C9and the ethyl cycloalkanes C5to C9(ring size in each case) by competitive oxidation of the cycloparaffins with cumene. In the case of the methyl and ethyl cycloalkanes the reactivities of the tertiary CH bonds could be calculated from the amounts of tertiary alcohols formed after LiAlH4reduction of the oxidates. As expected, the CH reactivities are especially low in six‐membered cycloparaffins and especially high in five‐, seven‐ and eight‐membered cycloparaffins. The CH reactivity of cyclododecane lies in the same order of magnitude as the reactivities of secondary CH bonds of n

ISSN:0941-1216    

DOI:10.1002/prac.19953370113

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

Acyloin Condensation of 1,2‐Diacyloxyethanes; Directed Synthesis of Unsymmetrically Substituted 1,2‐Bis‐(trimethylsiloxy)ethenesA synthesis specifically directed to unsymmetrically substituted 1,2‐bis‐(trimethylsiloxy)ethenes (2a–d), precursors of the corresponding acyloins, was accomplished by intramolecular acyloin condensation of the unsymmetrical 1,2‐diacyloxyethanes (1a–d) with sodium in toluene/chloro

ISSN:0941-1216    

DOI:10.1002/prac.19953370114

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

ISSN:0941-1216    

DOI:10.1002/prac.19953370115

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

ISSN:0941-1216    

DOI:10.1002/prac.19953370116

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

ISSN:0941-1216    

DOI:10.1002/prac.19953370117

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

ISSN:0941-1216    

DOI:10.1002/prac.19953370118

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

ISSN:0941-1216    

DOI:10.1002/prac.19953370120

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

Organosilicon Chemistry: From Molecules to MaterialsThe transition from basic to applied organosilicon chemistry is described for the research fields that are studied by the author's group: silaethene chemistry, organosilicon polymer chemistry with silacycles and the chemistry of higher coordinated silicon species.Early investigations started with the study of the pyrolysis of silacyclobutanes that yielded silaethenes in the gas phase. However, these investigations are tedious and are of little use for a widespread study of silaethene chemistry. Therefore the generation of silaethenes in solution (from vinylchlorosilanes andtert‐butyllithium) is the preferred method. Numerous differently substituted silaethenes have been generatedin situand their reactivity, especially in cycloaddition reactions, has been studied. Silaethenes that have two chlorine substituents at the silicon atom (especially Cl2SiCHCH2But) show an unusual cycloaddition reactivity and yield unexpected products with dienes and trienes (e. g. from [2+2] and [6+2]reactions); some of the silenes with donorfunctional groups at the α‐C‐atom undergo interesting intramolecular rearrangements. The cycloadducts of Si‐dichlorofunctional silenes also show rearrangements when thermolyzed (e. g. [2+2] → [4+2]adducts). The reactivity of these silaethenes and their cyclo‐adducts is due to the two chlorine atoms at the silicon atom and their influence can be explained by theoretical models.Silacycles synthesized from silaethenes have been incorporated or have been transformed into silicon containing polymers. Model compounds for nucleophilic substitution reactions at silicon centers and for the hydrolysis of chlorosilanes are higher coordinated silicon species up to coordination number „seven”︁. Some structures that describe such reactions have been characterized by X

ISSN:0941-1216    

DOI:10.1002/prac.19953370121

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY

摘要:

Geminal Substituent Effects. VIII. Enthalpies of Formation of AcetalsThe standard enthalpies of combustion ΔHc° (1 or c) of the α‐phenyl‐substituted acetals (1) and diacetals (2) were measured calorimetrically. The enthalpies of vaporisation or sublimation ΔHvapor ΔHsubof1–2were obtained from the temperature function of the vapor pressure measured in a flow system, and the standard enthalpies of formation are obtained thereof: ΔH°f(1 or c) and ΔHf° (g) (in kJ mol−1) for1a= −308.40 ± 0.52(1), −248.94 ± 0.88;1b= −343.48 ± 0.72 (1), −288.5 ± 1.5;1c= −267.4 ± 1.3 (1), −205.3 ± 1.3;1d= −343.8 ± 2.1 (c), −261.9 ± 2.2;1e= −397.02 ± 0.86 (c), −311.3 ± 1.2;1f= −414.52 ± 0.80 (1), −350.68 ± 0.86;2a= −564.8 ± 2.4 (c), −467.1 ± 2.5;2b= −547.6 ± 1.6 (c), −414.9 ± 2.7;2c= −717.1 ± 7.5 (c), −587.0 ± 8.0. The results are combined into values of two strain free group increments CH[20, CPh] = −59.7 and C[20, C

ISSN:0941-1216    

DOI:10.1002/prac.19953370122

出版商:WILEY‐VCH Verlag GmbH    

年代:1995

数据来源: WILEY