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

Abstract

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.