摘要:

AbstractIn contrast to the very large number of special methods applicable to syntheses in the heterocyclic series, relatively few general methods are available. The 1,3‐dipolar addition offers a remarkably wide range of utility in the synthesis of five‐membered heterocycles. Here the “1,3‐dipole”, which can only be represented by zwitterionic octet resonance structures, combines in a cycloaddition with a multiple bond system – the “dipolarophile” – to form an uncharged five‐membered ring. Although numerous individual examples of this reaction were known, some even back in the nineteenth century, fruitful development of this synthetic principle has been achieved o

ISSN:0570-0833    

DOI:10.1002/anie.196305651

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractNitrens are molecular fragments with six electrons on the nitrogen which are formed thermally or photochemically from hydrazoic acid or organic azides. Kinetics of the cleavage of azides, spectroscopic data, and electron spin resonance measurements constitute proof for a biradical nature of the nitrens studied. As a result of hydrogen shifts, nitrens are capable of isomerization to mines, of hydrogen abstraction from neighbouring molecules affording primary amines, and of ring formation by internal dehydrogenation (insertion reactions). Isomerization and hydrogen shifts are observed primarily with alkylnitrens; however, under favorable structural conditions, hydrogen shifts in arylnitrenes also lead to immines. Arylinitrens dimirize to azo compounds and undergo intra‐ and intermolecular reactions with nucleophilic reactants. Thus, both stable and unstable acylnitrenes, which are formed thermally or photolytically from acyl azides, add on, for example, to dimethyl sulfide or dimethyl sulfoxide, affording sulfimines or sulfoximines, respectively. Nucleophilic reagents, such as alcohols and amines, also react with nitrenes. Besides azides, anil‐N‐oxides also undergo cleavage to give nitrenes. The reaction of N‐chloramines and hydroxylamine‐O‐sulfonic acids with nucleophilic reagents probably does not proceed via a nitrene intermediate, but rathr by an SNmechanism. A crucial experiment differentiating between these two paths is described, and Rashig's hydrazine synthesis is discusse

ISSN:0570-0833    

DOI:10.1002/anie.196305991

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractFree dimethylketene is difficult to handle because of its tendancy to dimerize even at low temperatures and to from explosive peroxides with atmospheric oxygen. In contrast, the dimethylketenacylal of dimethylmalonic acid is simple and safe to use. This compound affords dimethylketene on thermal or catayltic cleavege, hence, it can replace the free ketene in nearly all reaction. The synthesis and reactions of this acylal are described.

ISSN:0570-0833    

DOI:10.1002/anie.196306081

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractCarbon tetrachloride can be prepared from phosgene at 300–450°C. The catalysts for the reaction are transition metals of Groups V to VIII deposited on activated charcoal as carrier. Carbon monoxide and chlorine may be used as starting materials instead of phosge

ISSN:0570-0833    

DOI:10.1002/anie.196306131

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196306151

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196306161

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196306173

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196306182

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196306193

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196306201

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY