N-Heterocyclic Carbene-Catalyzed Reaction of Chalcones and Enals via Homoenolate: an Efficient Synthesis of 1,3,4-Trisubstituted Cyclopentenes

摘要

The concept of homoenolate anions was introduced by Nickon and Lambert in their seminal paper in 1962.Their application in organic synthesis during the last four decades,however,was limited,presumably due to the difficulty in generating homoenolates directly.Helquist et al.were the first to circumvent this problem by using beta-propionaldehyde anion equivalent as a homoenolate equivalent.Subsequent efforts to generate homoenolate equivalents include the use of beta-propionate anion equivalent,cyclopropanone silyl hemiketal,and alpha-heteroatom-substituted allyl anion by a number of investigators.