Behavioral differences between the electrophilic reagents diethyltrichloromethylphosphonate and carbon tetrachloride in reactions with triethylphosphite

The reaction of triethylphosphite 1 with diethyltrichloromethylphosphonate 2b in the absence of solvents and catalysts yields mainly diethyl(1,1-dichl oropropyl)phosphonate 4 and diethyldichloromethylphosphonate 7. These main products are accompanied by a variety of by-products which differ considera bly from those obtained in the reaction between triethyl phosphite and CCl4 . Both reactions would begin by a halophilic substitution of triethylphosph ite on the positive halogen. For diethyltrichloromethylphosphonate 2b the f ormed carbanion would then attack preferentially the carbon beta to P+ and the hydrogen gamma to P+ on heterophosphonium cation. In contrast, the less sterically hindered trichloromethyl carbanion formed by the halophilic att ack of triethylphosphite on carbon tetrachloride would rather attack mainly the positive P+ of this cation. The tetraethyl(dichloromethylene)bisphosph onate 8 previously reported by Kukhar and Sagina to be the main product for med in the thermal reaction between triethylphosphite and diethyltrichlorom ethylphosphonate was not found under our conditions. We observed its format ion only under photochemical irradiation.