Chemo- and Enantioselective Bronsted Acid-Catalyzed Reduction of α-Imino Esters with Catecholborane

The chemo- and enantioselective reduction of alpha-imino esters with catecholborane has been developed employing 10 mol% of an enantiopure BINOL-based phosphoric acid as organocatalyst. Various differently substituted aromatic alpha-amino acid derivatives can be achieved in almost quantitative yields and very good to excellent enantioselectivities of up to 96% ee under mild reaction conditions.