Structure of the indene-3-acetic acids. Part II. Reformatsky reactions of 6-benzyloxy-, 5,6-dimethoxy-, and 6-methoxy-indan-1-ones

Abstract

Reformatsky reactions of ethyl bromoacetate with indan-1-ones usually gave mixtures of the endo- and exo-unsaturated esters, but the reaction with 5,6-dimethoxyindan-1-one gave solely the exo-isomer. Hydrolysis of the esters from the title indan-1-ones gave mixtures of the isomeric acids, except in the last case, when 5-methoxy-indene-3-acetic acid alone was obtained. It is concluded that the functional role of the aryl substituent in providing an extended conjugated system favours exo-unsaturation.