Dialkyl phosphonates and tetraalkyl bis(phosphonate)s from the decomposition of quasi-phosphonium ylidic phosphonates in aqueous conditions

Abstract

The reaction of dimethyl benzoylphosphonates 1 (X = 2-halogen or 2-CF₃O) with trialkyl phosphite leads to the formation of carbene intermediates 3 which are trapped by trialkyl phosphite to give the corresponding ylidic phosphonates 4. In acidic conditions these ylidic phosphonates decompose to give tetraalkyl phenylmethylene-1,1-bis(phosphonate)s 6 but in neutral or basic conditions they give mainly dimethyl benzylphosphonates and trialkyl phosphate. Factors influencing the mode of decomposition have been investigated.