Chiral Brønsted Acid Catalysis for Enantioselective Hosomi−Sakurai Reaction of Imines with Allyltrimethylsilane

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