Utilização de enecarbamatos endociclicos contendo auxiliares quirais frente a reação de cicloadição [2+2] com cetenos e a reação de Heck com sais de diazonio

AUTOR(ES)
DATA DE PUBLICAÇÃO

2001

RESUMO

N-Protected five-membered endocyclic enecarbamates bearing carbo-8-phenylmenthoxy, 8-(p-nitrophenyl)menthoxy or 8-[p-(N, N-methyl-methoxycarbonyl)aminophenyl]menthoxy, as chiral auxiliares, were prepared average yields of 40%. The p-nitro and p-(N, N-methyl-methoxycarbonyl)amino substituted enecarbamates were submitted to the [2+2] cycloadittion reaction with dichloroketene yielding (1R, 5S) and (1S, 5R) azadichlorocyclobutanones as a diastereomeric mixture in a ratio of 1: 1,5 and 1,25: 1, in 76% and 70% yields respectively. These results were compared with previously ones obtained in the research group (4:1, (1R, 5S)/(1S, 5R) when 8-phenylmenthol were the chiral auxiliar) and they confirm the relevance of the eletronic effects (p-stacking) associated with the use of 8-arylmenthols as chiral auxilires. As an extension of this study, the enecarbamates containing the chiral auxiliares 8-phenylmenthol or 8-(p-nitrophenyl)menthol were submitted to a Heck arylation protocol with p- methoxyphenyldiazonium tetrafluoroborate. These reactions yielded 8-phenylmenthyl and 8-(p-nitrophenyl)menthyl 2-(p-methoxyphenyl)-3-pirrolinecarboxylates as a 3,5:1 and 7:1 (S:R) diastereomeric mixture in 86% and 70% yield respectively.

ASSUNTO(S)

paladio quimica organica compostos aromaticos fenois

ACESSO AO ARTIGO

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