Highly enantioselective intermolecular alkylation of aldehydes with alcohols by cooperative catalysis of diarylprolinol silyl ether with Brønsted acid

Two cooperative systems: I/2,3,4-trihydroxybenzoic acid and I/TfOH effect highly enantioselective intermolecular α-alkylation of aldehydes. These systems afford functionalized aldehydes in high yields, and with excellent ee and de values with broad substrate scope (see scheme; R¹=alkyl, R²,R³=aryl, or R²=ferrocenyl, R ³=phenyl, or R²=indolyl, R³=phenyl).