Chiral Bronsted Acid Catalysis for Enantioselective Hosomi-Sakurai Reaction of Imines with Allyltrimethylsilane

The chiral Bronsted acid (1b or 1c) has been shown to initiate the Hosomi-Sakurai reaction of imines with excellent enantioselectivities. The combined Bronsted acid system has been developed to offer a new class of chiral Bronsted acid catalysis. The present system proceeds through regeneration of the chiral Bronsted acid by proton transfer from additional Bronsted acid to silylated chiral Bronsted acid, a newly elucidated mechanism for the role of the additional Bronsted acid.