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 (SP)-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.