Asymmetric conjugate addition

Abstract

Abstract The conjugate addition, the most popular reaction in organocopper chemistry, is very well suited for the formation of new stereogenic centres. Several examples of very high levels of diastereoselectivity show that organocopper reagents are very sensitive to the steric and electronic environment of the prochiral sp2 carbon β to the carbonyl. Owing to the importance of this synthetic transformation it is not surprising that the asymmetric version of this reaction was attempted at the very early stages of the organocopper era. There are several ways to attain this goal. The most obvious one is to attach covalently a chiral auxiliary, do a diastereoselective conjugate addition, and then remove this chiral auxiliary, the overall result being an enantioselective transformation. This chiral auxiliary may be placed either on the electrophile or on the R group of the organocopper reagent itself.