The First Enantioselective Halo Aldol Reaction of Ethyl Propiolate and Aldehydes

✍ Scribed by Dianjun Chen; Cody Timmons; Junying Liu; Allan Headley; Guigen Li

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 127 KB
• Volume: 2004
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.200400230

✦ Synopsis

Abstract

The first enantioselective halo aldol reaction of ethyl propiolate with aldehydes has been established by using Jacobsen’s chiral cyclohexylsalen ligand. The reaction was conducted at −20 °C in dichloromethane with Et~2~AlI as the source of halogen and Lewis acid promoter. Excellent geometric selectivity (only the Z isomer) has been achieved for all 14 examples examined. The reaction works well with aromatic aldehydes; it also works with aliphatic aldehydes and α,β‐unsaturated aldehydes, albeit with diminished yields and ee. This method provides the first enantioselective synthesis of β‐iodo Morita−Baylis−Hillman (MBH) esters. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)