SYNTHESIS OF PARTIALLY HYDROGENATED 2,2'-BIS(DIPHENYLPHOSPHENYL)-1,1'-BINAPHTHYL (BINAP) LIGANDS AND THEIR APPLICATION TO CATALYTIC ASYMMETRIC HYDROGENATION

Three pairs of new axially dissymmetric bisphosphane ligands, (R)-(-)- and (S)-(+)-2,2'-bis-(dicyclohexylphosphanyl) -1,1'-binaphthyl[(R)-(-)- and (S)-(+)-Cy-BINAP, (R)-(-)- and (S)-(+)-2], (R)-(+)- and (S)-(-)-2,2'-bis(diphenylphosphanyl) -5,5',6,6',7,7',8,8'-octahydro-1,1'-binaphthyl [(R)-(+)- and (S)-(-)-H-8-BINAP, (R)-(+)- and (S)-(-)-3], and (R)-(-)- and (S)-(+)-2,2'-bis(dicyclohexylphosphanyl) -5,5',6,6',7,7',8,8'-octahydro-1,1'-binaphthyl [(R)-(-)- and (S)- (+)-cy-H-8-BINAP, (R)-(-)- and (S)-(+)-4], have been synthesized. The absolute configurations of the isomers 2 were determined by single-crystal X-ray diffraction of the linear 1:1 polymeric complex of (S)-(+) -2,2'-bis(dicyclohexylphosphinoyl)-1,1'-binaphthyl [(S)-(+)-Cy-BINAPO, (S)-(+)-6] and (2R,3R)-(-)-di-O-benzoyltartaric acid [(-)-DBT], and those of the isomers 3 and 4 were established on the basis of CD spectra of the phosphanes and their bisoxides. X-Ray crystallographic studies of two cationic Rh-I complexes, [Rh{(S)-Cy-binap}(cod)]CIO4 [(S)-17]+ and [Rh{(S)-H-8-binap}(cod)]CIO4[(S)-18], revealed that complex (S)-17 possesses a dissymmetric structure, while complex (S)-18 has a pseudo-C-2-symmetry and shows a significantly large dihedral angle between the two phenyl rings [80.3(4)degrees]. The potentiality of ligand 3 for asymmetric catalysis was demonstrated in Ru-II-catalysed stereoselective hydrogenations of methyl 2-(benzamidomethyl)-3-oxobutanoate (21, in up to 92% d.e. and 99% e.e.) and geraniol (22, in 98% optical purity).