Chiral Proton-Transfer Shuttle Catalysts Promoted Enantio­selective Nazarov Cyclization

Abstract

AbstractThe Nazarov cyclization reaction is a convenient, widely used method for the synthesis of cyclopentenones. In this account, we reviewed our recent efforts on the chiral proton-transfer shuttle catalysts promoted enantioselective Nazarov cyclization. We have synthesized various chiral cyclopenta[b]indoles and chiral α,α′-disubstituted cyclopentenones by means of cooperative catalysis of a Lewis acid and a chiral spiro phosphoric acid. The mechanistic studies revealed that the chiral spiro phosphoric acid acts as a multifunctional catalyst: it co-catalyzes the cyclization of the dienone and enantioselectively catalyzes a proton-transfer reaction of the enol intermediate via a hydrogen-­bonding network.1 Introduction2 Enantioselective Nazarov Cyclization of Indole Enones3 Enantioselective Silicon-Directed Nazarov Cyclization4 Conclusion