Scope and limitations of the Pd(II)-catalyzed cycloisomerization of functionalized 1,5-hexadienes have been studied. In situ NMR experiments indicate a challenging competition between various reaction pathways. A careful balance between substrate structure, nature of the precatalyst, and reaction conditions was required to gain access to a useful building block for sesquiterpene total synthesis.
The Catalytic Enantioselective Claisen Rearrangement of an Allyl Vinyl Ether
Gosteli−Claisen Rearrangement: Substrate Synthesis, Simple Diastereoselectivity, and Kinetic Studies
作者:Julia Rehbein、Sabine Leick、Martin Hiersemann
DOI:10.1021/jo802303m
日期:2009.2.20
kinetic studies on the uncatalyzed [3,3]-sigmatropic rearrangement of 2-alkoxycarbonyl-substituted allyl vinyl ethers are reported. Apparently first reported by Gosteli in 1972, this variation of a Claisenrearrangement enjoyed a shadowy existence for three decades until its potential for the development of a catalytic asymmetric Claisenrearrangement was discovered. Inspired by this development, we have
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.