Synthesis of racemic P-chiral phosphine oxides and phosphonium salts by stepwise reaction of phosphacoumarins with organomagnesium compounds

Abstract A new effective synthetic route to the racemic phosphine oxides and phosphonium salts with a P-asymmetric center was developed based on the stepwise reaction of phosphacoumarins with organomagnesium compounds. A selective P–C bond formation was achieved on each step owing to the differences in reactivity of the exocyclic P–Cl or P–O bonds and endocyclic P–O bond of phosphacoumarins. It was found that the P(O)OMgX fragment of the phosphocoumarin salt does not hinder in the substitution reaction at the phosphorus atom accompanied by ring-opening and P–C bond formation.