A method for the synthesis of O, O-diethyl (N-benzoyl)trichloroacetimidoylphosphonate (1) by successive reaction of N-(1-diethoxyphosphoryl-2,2-dichlorovinyl)benzamide with Me3SiCl and Cl-2 was proposed. The reaction of phosphonate 1 with R3P follows the [4+1] cycloaddition mechanism to give phosphoranes, whose stability and further transformations are controlled by the nature of R.