Hydrophosphination
of bicyclo[1.1.0]butyl nitriles with phosphine
boranes and phosphites provided novel cyclobutyl-P derivatives. The
reaction generally favors the <i>syn</i>-diastereomer, and
the nitrile can be reduced and converted to other functional groups,
thus enabling the preparation of bidentate ligands that access new
conformational space by virtue of their attachment to the torsionally
malleable but sterically restrictive cyclobutane scaffold. The enantioselective
hydrogenation of dehydrophenylalanine using a bidentate phosphine–phosphite
ligand illustrates the synthetic utility of the newly prepared scaffold