Convergent asymmetric disproportionation reactions: metal/Brønsted acid relay catalysis for enantioselective reduction of quinoxalines

J Am Chem Soc. 2011 Apr 27;133(16):6126-9. doi: 10.1021/ja200723n. Epub 2011 Apr 5.

Abstract

A convergent asymmetric disproportionation of dihydroquinoxalines for the synthesis of chiral tetrahydroquinoxalines using a metal/Brønsted acid relay catalysis system has been developed. The use of hydrogen gas as the reductant makes the convergent disproportionation an ideal atom-economical process. A dramatic reversal of enantioselectivity was observed in the reduction of quinoxalines because of the different steric demands in the 1,2- and 1,4-hydride transfer pathways.