Enantioselective Protonation Catalyzed by Chiral Br^|^oslash;nsted Bases

Abstract

The proton is the smallest group in synthetic organic chemistry. Moving a proton within a catalytic cycle in an enantioselective manner is a formidable task that has attracted the attention of many chemists. Furthermore, catalytic enantioselective protonation is an atom economical method of generating chiral carbon centers. Variations of this kind of reaction catalyzed by transition metals catalysts have been well investigated. On the other hand, a complementary approach to this reaction, the use of chiral Brønsted base catalysts is relatively less explored. We have developed several protonation reactions using chiral bicyclic guanidine as the Brønsted base catalyst. In this review, we will report these reactions and other related examples recently described by other groups.