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Synthesis of Functionalized Carbamates through a Palladium‐Catalyzed Reductive Carbonylation of Substituted Nitrobenzenes

 

作者: Petra Wehman,   Leo Borst,   Paul C. J. Kamer,   Piet W. N. M. Van Leeuwen,  

 

期刊: Chemische Berichte  (WILEY Available online 1997)
卷期: Volume 130, issue 1  

页码: 13-22

 

ISSN:0009-2940

 

年代: 1997

 

DOI:10.1002/cber.19971300104

 

出版商: WILEY‐VCH Verlag

 

关键词: Carbamates;Catalysis;Substituted nitrobenzenes;Palladium;Reductive carbonylation

 

数据来源: WILEY

 

摘要:

AbstractThe palladium‐catalyzed reductive carbonylation oforthoandpara‐substituted nitrobenzenes has proven to be an attractive route for the synthesis of functionalized carbamates. For the Pd(1, 10‐phenanthroline)2(triflate)2catalyst system, the scope of the reaction has been studied. Substrates with electron‐donating substituents at theparaposition were found to decrease the catalytic activity, most probably as a result of their relatively low oxidizing capacity. the selectivity towards the desired carbamate, however, was increased for these substrates. Under the influence of electron‐withdrawing substituents the azoxybenzene and azobenzene derivatives became important side products. Introduction of large steric hindrance at theorthoposition of the nitro substrates gave rise to an interesting side reaction, viz. methoxylation of the aromatic ring. The methoxylation reaction appeared to occur on an intermediate species in the catalytic cycle. Several functionalities have shown to be resistant to the reaction conditions required for the conversion ot the nitro group. Especially with 4‐nitrobenzoic acid, an extremely high activity and selectivity was found, thus yielding a very convenient synthesis forN‐protected amines containing carboxylic

 

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