1,1-P-OP Ligands with P-Stereogenic Phosphino Groups in Asymmetric Hydrogenations and Hydroformylations

A new series of narrow-bite-angle phosphine–phosphite (1,1-P–OP) ligands (3a–d) has been efficiently prepared from the enantiopure (S_P)-tert-butyl(hydroxymethyl)methylphosphino borane complex 1, a crucial intermediate. The catalytic performance of the ligands in Rh-mediated asymmetric hydrogenations and hydroformylations is described. The corresponding rhodium complexes provided excellent efficiencies (full conversion in all cases) and high enantioselectivities (up to 98% ee) for the asymmetric hydrogenation of structurally diverse functionalized alkenes. Furthermore, rhodium catalysts derived from these 1,1-P–OP ligands were highly active and gave excellent regioselectivities (branched/linear product ratios of up to 97/3) and moderate enantioselectivities in the hydroformylation of different terminal olefins.