Synthesis of <i>P</i>,<i>P</i>-heterotopic binaphthyldiphosphanes (BINAPP') devoid of <i>C</i>₂ symmetry from 2,2'-binaphthol

Abstract

The introduction of two nonequivalent diarylphosphanyl substituents into the 2- and 2'-positions of 1,1'-binaphthalene has been successfully accomplished in four steps from 1,1'-binaphthalene-2,2'-diol (BINOL) through conversion into the ditriflate followed by sequential substitution of triflate groups mediated by palladium or nickel catalysts. The selective monosubstitution of the triflate has been achieved by introducing the first phosphorated substituent in the form of phosphane oxide through a Pd-catalyzed reaction. The otolyl- substituted diphosphane 4c is a chiral inducer that is more efficient than BINAP both in the Rh-catalyzed asymmetric hydrogenation of acetamido acrylic acid derivatives and in the Pd-catalyzed allylic alkylation of 1,3-diphenylprop- 2-enyl acetate (85% ee)