Highly Enantioselective Iridium-Catalyzed Hydrogenation of Cyclic Enamides

Abstract

The MaxPHOX-Ir catalyst system provided the highest selectivity ever reported for the redn. of cyclic enamides derived from α- and β-tetralones. This result indicates that iridium catalysts are also proficient in reducing alkenes bearing metal-coordinating groups. In the present system, selectivity was pressure-dependent: in most cases, a decrease in the H2 pressure to 3 bar resulted in an increase in enantioselectivity. Moreover, the process can be carried out in environmentally friendly solvents, such as methanol and Et acetate, with no loss of selectivity.