Unexpected rapid P -stereomutation of phosphine oxides catalysed by chlorophosphonium salts.

P -Stereomutation of phosphine oxides is extremely slow. We show that it is catalysed by chlorophosphonium salts (CPS) which can directly be formed in the system in situ . The racemization of phosphine oxides at ambient conditions catalysed by 1 mol% of CPS takes 1-2 hours and can be arrested by additon of a primary alcohol. The process probably proceeds via the development of oxodiphosphonium P-O-P species.