Facile synthesis of various 4-carboxylic acid derivatives and their amide analogues of benzopyrans

摘要

A series of 4-carboxyalkyl amide derivatives of benzopyrans 6a-d and 7a-d have been prepared in 40-64% overall yields. In the proposed synthetic strategy, the key intermediate 4-methyl substituted chroman 3 is obtained by condensing substituted phenol and mesityl oxide in presence of PPA. The required carboxylic acid function has been introduced at C-4 in benzopyran ring through a novel route.