Synthèse régiosélective par voie organomagnésienne de 2-(1,1-dialkylprop-2-ényl)-4,5-dihydrothiazoles et oxazoles, précurseurs d'acides β-éthyléniques α,α-disubstitués
摘要:
The synthesis of new 4,5-dihydrothiazoles (or oxazoles) starting from 2-methylthio-4,5-dihydrothiazoles (or oxazoles) and beta,beta-disubstituted allylic Grignard reagents has been described. Acidic hydrolysis of many of these heterocycles leads to the corresponding alpha, alpha-disubstituted beta-ethylenic carboxylic acids.
Alkylation of lithium dienediolates of butenoic acids. Regioselectivity effects of structure and leaving group of the alkylating agent
作者:Maria J. Aurell、Salvador Gil、Ramon Mestres、Margarita Parra、Lilian Parra
DOI:10.1016/s0040-4020(98)00149-5
日期:1998.4
Regioselectivity of alkylation of but-2-enoic acids 1 and 2 by alkyl halides strongly depends on the reactivity of the electrophile. High α selectivity results for saturated alkyl halides, whereas poor α-selectivity is obtained for highly reactive allyl and benzyl halides. For reactive alkylating halides selectivity is partly governed by the ion pairing aggregates of the dienediolates. Lithium bromide