Ring expansion reactions of P&z.dbd;O-containing molecules

A series of ring expansion reactions of P&z.dbd;O-containing molecules have been developed for the synthesis of medium-sized ring cyclic phosphonate esters and phosphonamidates. The reactivity trends initially appear to be counter-intuitive, compared with more well established ring expansion reactions of lactam derivatives, but are explained by considering the differences in heteroatom bonding to P and C respectively. A series of ring expansion reactions of P&z.dbd;O-containing molecules have been developed for the synthesis of medium-sized ring cyclic phosphonate esters and phosphonamidates.