Iron-Catalyst-Switched Selective Conjugate Addition of Grignard Reagents:alpha,beta,gamma,delta-Unsaturated Amides as Versatile Templates for Asymmetrie Three-Component Coupling Processes

摘要

Conjugate addition of Grignard reagents to alpha,beta-unsaturated carbonyl compounds is one of the most fundamental methods for carbon-carbon bond formation and is usually carried out with copper catalysis.Among the various kinds of carbonyl compounds employed for this procedure,dienic substrates have not been amply investigated,presumably as a result of the accumulated difficulties in controlling both regio-and stereoselections,as shown in Scheme 1.We report herein that alpha,beta,gamma,delta-unsaturated amides work as a simple yet versatile template to circumvent this problem,where the absence or presence of an iron catalyst,rather than the aforementioned copper catalyst,is another key to achieving clear-cut reactions.