Secondary phosphine oxides (SPOs) are important starting materials in organophosphorus syntheses, and may be the ligands in transition metal complexes. SPOs are obtained from phosphorus trichloride via double substitution by a Grignard reagent followed by hydrolysis, or from dialkyl phosphites by reaction with two equivalents of a Grignard reagent. The preparation of SPOs with two different substituents is of special importance. This minireview gives useful hints for the synthesis of a variety of SPOs that are useful intermediates.
Keywords: Dialkyl phosphites, grignard reagents, P(III)-chlorides, secondary phosphine oxides, substitution, ligand.