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A series of novel optically active diphosphine ligands, (4,4′‐bi‐1,3‐benzodioxole)‐5,5′‐diylbis(diarylphosphine)s (6), which are called SEGPHOS, has been designed and synthesized with dihedral angles in the Ru complexes being less than that in the corresponding BINAP‐Ru complex. The stereorecognition abilities of SEGPHOS‐Ru complex catalysts in the asymmetric catalytic hydrogenation of a wide variety of carbonyl compounds are superior to those observed with BINAP‐Ru complex catalysts.

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Practical methods for the synthesis of (R)or (S)-2,2'-bis(diarylphosphino)-l,l'-binaphthyls (BINAPs), useful ligands for transition-metal-catalyzed asymmetric reactions, have been developed. (±)-2,2'-Bis(diphenylphosphinyl)-l,l'-binaphthyl [(±)-BINAPO], prepared from 2,2'-dibromo-l,l'-binaphthyl and diphenylphosphinyl chloride, can be resolved into optical antipodes by the use of camphorsulfonic acid or 2,3-di-O-benzoyltartaric acid. Reduction of resolved BINAPO with trichlorosilane in the presence of triethylamine affords optically pure 2,2'-bis(diphenylphosphino)-l,l'-binaphthyl (BINAP). In a similar manner, several BINAP analogues have been prepared in optically pure form. The present procedures are suitable for obtaining these axially dissymmetric diphosphines in a large scale. The molecular structure of the 1:1:1 complex of (S)-(-)-BINAPO, (lR)-(-)-camphorsulfonic acid, and acetic acid has been studied by single-crystal X-ray analysis.Recently numerous chiral di-terf-phosphines have been devised as ligands for transition-metal-catalyzed asym-metric syntheses in the homogeneous phase.1 Some years ago, we reported (R)or (S)-2,2'-bis(diphenyl-