The chiralBrønstedacid (1b or 1c) has been shown to initiate the Hosomi−Sakurai reaction of imines with excellent enantioselectivities. The combined Brønstedacid system has been developed to offer a new class of chiralBrønstedacidcatalysis. The present system proceeds through regeneration of the chiralBrønstedacid by proton transfer from additional Brønstedacid to silylated chiral Brønsted