A chelating diphosphine with a single stereogenic phosphorus atom; RP or SP-(2-methoxyphenyl)-P-phenyl-P-(2′-diphenylphosphino)ethylphosphine

Abstract A synthesis of the title diphosphine is described, in which the key step is a Michael addition of lithium diphenylphosphide to a vinylphosphineborane 9 , itself formed by stereospecific ring opening of the ephedrine-derived oxazaphospholidine borane by reaction with vinyl lithium. The resulting phosphinamide 11 can be further elaborated to the desired product R-5 in 96% e.e., superior to that obtained in a parallel synthesis involving the vinylphosphine oxide 1 In the latter case enantiomerically pure S-product can be obtained by recrystallisation of palladium complex 7 and recovery of the diphosphine by displacement with KCN.