Synthesis of a Novel Chiral Binaphthyl Phospholane and Its Application in the Highly Enantioselective Hydrogenation of Enamides

A new chiral phosphine, (R,R)-1,2-bis{(R)-4,5-dihydro-3H-dinaphtho[2,1-c:1‘,2‘-e]phosphepino}benzene {abbreviated as (R,R)-binaphane] was prepared on the basis of a practical route from a readily accessible enantiomerically pure binaphthanol. This ligand possesses both binaphthyl chirality and phospholane functionality. Excellent enantioselectivities (95−99.6% ee) have been observed in hydrogenation of an isomeric mixture of (E)- and (Z)-β-substituted-α-arylenamides by using a Rh−binaphane catalyst. These enantioselectivities are the highest reported to date for this transformation.