Steric course of cross coupling of organocopper reagents with allylic acetates

Abstract

The trans- and cis-2-methyl-1-vinylcyclohexyl acetates (4b) and (5b) were prepared from 2-methylcyclohexanone (1). The stereochemistry of the reaction of these isomers when treated with lithium dialkylcopper reagents is investigated and the structures are confirmed by ¹³C n.m.r. spectroscopy. The stereoselectivity experienced in the conversion of the cis-compound (5b) into the E-olefins (7a and b) is not observed with the trans-analogue (4b). This is tentatively interpreted in terms of steric hindrance during the attack of the reagent in the case of (5b).