Identification of a key intermediate in the asymmetric Appel process: one pot stereoselective synthesis of P-stereogenic phosphines and phosphine boranes from racemic phosphine oxides

Sequential treatment of racemic phosphine oxides with oxalylchloride and chiral non-racemic alcohol generates the sameratios of diastereomeric alkoxyphosphonium salts obtained inthe corresponding asymmetric Appel process, strongly implicatingthe intermediate chlorophosphonium salt in the stereoselectingstep. Subsequent reduction allows a novel synthesis of enantioenriched P-stereogenic phosphines-phosphine boranes.