Study on the Atherton–Todd reaction mechanism†
A new mechanism of the Atherton–Todd reaction is discussed. The first step of the reaction between diesters of H-phosphonic acid and carbon tetrachloride in the presence of a base, commonly triethylamine, is a salt formation between carbon tetrachloride and the base [amine·Cl]+CCl3−. The trichloromethanide anion [CCl3−] deprotonates dialkyl H-phosphonate to form chloroform and dialkyl phosphonate anion [(RO)2P(O)]−. The latter anion reacts with the chlorine cation to furnish dialkyl chlorophosphate. Based on these findings the reaction has been applied for the oxidation of poly(alkylene H-phosphonate)s to the corresponding poly(alkylene chlorophosphate)s via the Atherton–Todd reaction.