Synthesis of α-Allyloxy-Substituted α,β-Unsaturated Esters via Aldol Condensation. Convenient Access of Highly Substituted Allyl Vinyl Ethers
作者:Martin Hiersemann
DOI:10.1055/s-2000-6424
日期:——
α-Allyloxy-substituted α,β-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 α-allyloxy-substituted ester 2a - i and an aldehyde R1CHO followed by mesylation and DBU mediated elimination to afford the 2-alkoxycarbonyl-substituted allyl vinyl esters 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 R1. Z:E ratios from 3:2-9:1 were obtained.
Synthesis and Lewis acid catalyzed Claisen rearrangement of 2-(1,3-oxazolin-2-yl)-substituted allyl vinyl ethers
作者:Hannes Helmboldt、Martin Hiersemann
DOI:10.1016/s0040-4020(03)00590-8
日期:2003.6
Allylvinylethers containing an acceptor function in the 2-position are useful substrates for the Lewis acid-catalyzed Claisenrearrangement. The first synthesis of acyclic 2-(1,3-oxazolin-2-yl)-substituted allylvinylethers is reported. The Lewis acid catalyzed Claisenrearrangement of these allylvinylethers afforded the rearrangement products with low to moderate diastereo- and enantioselectivity