2-diphenylphosphino-2'-diphenylphosphinyl-1,1'-binaphthalene (BINAPO), an axially chiral heterobidentate ligand for enantioselective catalysis

Racemic 2-diphenylphosphino-2'-diphenylphosphinyl-1,1'-binaphthalene (BINAPO) 5 has been prepared in four steps from 1,1'-binaphthalene-2,2'-diol (BINOL) 1 and has been resolved with the aid of the C,N-cyclopalladated complex with N,N-dimethyl (S)-1-(1-naphthyl)ethylamine 6. P,O-chelate binding to palladium occurs in solution and this is confirmed in the solid state by X-ray analysis. (S)-BINAPO is an immediate precursor of (S)-BINAP and is itself an effective chiral inducer for the Pd-catalyzed asymmetric hydrosilylation of styrene (over 70% e.e.).