Studies on the activation pathway of phosphonic acid using acyl chlorides as activators

Abstract

The activation pathway of phosphonic acid with acyl chlorides has been investigated with the aim of evaluating the synthetic utility of the intermediates involved for the preparation of hydrogen-phosphonate (H-phosphonate) monoesters. It is found that, depending on the amount of condensing reagent used, three distinctive intermediates are potentially formed, namely the pyrophosphonate (2), the phosphono-acyl mixed anhydride (3a), and the triacyl phosphite (4a). Their chemical reactivities towards oxygen nucleophiles indicate that the most suitable intermediate for H-phosphonate monoester synthesis is the pyrophosphonate (2).