Synthesis of α-allyloxy-substituted α,β-unsaturated esters via aldol condensation.: Convenient access to highly substituted allyl vinyl ethers

alpha-Allyloxy-substituted alpha,beta-unsaturated esters 1a-r have been prepared in 5 steps from commercially available starting materials. The key sequence of the synthesis is an aldol addition between an alpha-allyloxy-substituted ester 2a-i and an aldehyde (RCHO)-C-1 followed by mesylation and DBU mediated elimination to afford the 2-alkoxycarbonyl-substituted allyl vinyl ethers 1a-r. The E/Z ratio of the newly generated vinyl ether double bond is apparently determined by the steric bulk of the vinyl ether double bond substituent R-1. Z:E ratios from 3:2-9:1 were obtained.