Preparation of Enantiomerically Pure 2‘-Substituted 2-Diphenylphosphino-1,1‘-binaphthyls by Reductive Cleavage of the Carbon−Phosphorus Bond in a Borane Complex of 2-Diphenylphosphino-2‘-diphenylphosphinyl-1,1‘-binaphthyl

Reaction of (S)-2'-boranatodiphenylphosphino-2-diphenylphosphinyl-1,1'-binaphthyl (3, borane complex of BINAP monoxide) with an excess of n-butyllithium in THF at -78 degrees C brought about a selective cleavage of the carbon-phosphorus bond between the binaphthyl and diphenylphosphinyl groups to generate the binaphthyllithium 14, the treatment of which with electrophiles MeOD, I(2), and ClSnMe(3) gave, after removal of the borane, the corresponding 2'-substituted 2-diphenylphosphino-1,1'-binaphthyls (E-MOP 9: E = D, I, SnMe(3)), without loss of the enantiomeric purity.