Asymmetric Hydrogenation of Quinoxalines with Diphosphinite Ligands: A Practical Synthesis of Enantioenriched, Substituted Tetrahydroquinoxalines

An easily accessible chiral Ir/H8-binapo catalyst exhibits unprecedented reactivity and excellent enantioselectivity in the hydrogenation of quinoxalines at a high ratio of substrate to catalyst (from 100 to 20 000). This new method provides a practical synthetic approach to give optically active chiral tetrahydroquinoxaline derivatives (see scheme; cod=1,5-cyclooctadiene).