Rh₂(OAc)₄ and chiral phosphoric acid cocatalyzed highly diastereo- and enantioselective four-component reactions: Facile synthesis of chiral α,β-diamino acid derivatives

A highly diastereo- and enantioselective four-component reaction of a diazo ketone with two molecules of anilines and ethyl glyoxylate was achieved under Rh₂(OAc)₄ and chiral phosphoric acid cocatalyzed conditions. This transformation proceeds through a Mannich-type trapping of the ammonium ylide generated from metal carbene and one molecule of aniline with iminoester derived from another molecule of aniline and ethyl glyoxylate. With this method, a series of chiral α,β-diamino acid derivatives were efficiently constructed in good yields and with good to excellent diastereo- and enantioselectivities.