Optically active diphosphine compound, method for making the compound, transition metal complex having the compound as ligand and method for making optically active substance by use of the complex

A method for making an optically active diphosphine compound represented by the following formula:

• ##STR20## where Ph is a phenyl group, X is a chlorine or bromine atom, and R.sup.1 and R.sup.2 are each an alkyl group having 1 to 3 carbon atoms said method comprising
• (A) reacting an optically active 2,2'-dihydroxy-5,5'-dihalo-4,4',6,6'-tetraalkyl-1,1'-biphenyl ditriflate represented by the following formula:
• ##STR21## where X, R.sup.1 and R.sup.2 are as defined above and Tf is a trifluoromethanesulfonyl group with a diphenylphosphine oxide, to prepare an optically active monophosphinyl monotriflate derivative represented by the following formula:
• ##STR22## where Ph, X, R.sup.1, R.sup.2 and Tf are as defined above, and reducing the thus obtained compound to prepare an optically active monophosphinomonotriflate derivative represented by the following formula:
• ##STR23## where Ph, X, R.sup.1 , R.sup.2 and Tf are as defined above, and (B) reacting the monophosphinomonotriflate derivative of the formula (4) with a diphenylphosphine oxide to prepare an optically active diphosphine oxide compound represented by the following formula:
• ##STR24## where Ph, X, R.sup.1 and R.sup.2 are as defined above and reducing the thus obtained compound.