The dienolate aldol reaction of (E)-N-crotonoyl C(4)-isopropyl SuperQuat: asymmetric synthesis of alpha-vinyl-beta-hydroxycarboxylic acid derivatives and conversion to alpha-ethylidene-beta-hydroxyesters (beta-substituted Baylis-Hillman products)

Journal article

The synthesis of α-vinyl-β-hydroxyesters and α-ethylidene-β-hydroxyesters (β-substituted Baylis-Hillman products) via the dienolate aldol reaction of (E)-N-crotonoyl C(4)-isopropyl SuperQuat is described. High levels of syn-diastereoselectivity (up to >98% de) are observed for the dienolate aldol reaction with boron enolates, generated either directly with Bu2BOTf or by transmetalation of the potassium enolate with B-bromocatecholborane. Cleavage of the resultant syn-aldol products from the auxiliary gives α-vinyl-β-hydroxyesters in >98% de and >98% ee. Subsequent isomerisation of the double bond into conjugation provides α-ethylidene-β-hydroxyesters (β-substituted Baylis-Hillman products) in high diastereo- and enantiopurity (≥91:9 [(E):(Z)] and >98% ee). © 2009 Elsevier Ltd. All rights reserved.

Authors: Davies, S; Elend, D; Jones, S; Roberts, P; Savory, E

• Publication status: Published
• Journal: TETRAHEDRON
• Volume: 65
• Issue: 37
• Pages: 7837-7851
• Publication date: 2009-09-12
• DOI: 10.1016/j.tet.2009.07.004
• ISSN: 0040-4020
• Language: English
• Keywords: Asymmetric synthesis; Baylis-Hillman; SuperQuat; Dienolate aldol