A Convenient Synthesis of Dibenzyl α,α-Difluoromethyl-β-ketophosphonates

Abstract

The first synthesis of dibenzyl α,α-difluoro-β-ketophosphonates has been accomplished by an original fluorination reaction, namely addition of the F+ ion to the enolate form of the corresponding dibenzyl β-ketophosphonate. After an easy cleavage of the benzyloxy protecting groups on the phosphorus atom, α-fluoro-β-ketophosphonic acids were subsequently obtained as stable carboxyphosphate mimics. This approach enables α,α-difluoro-β-ketophosphonate moieties to be introduced into multiply functionalised molecules, thus making the previously described diethyl phosphonate route no longer relevant. Moreover, study of their stability under neutral and basic conditions showed the importance of the keto-enol equilibrium in the decomposition pathway of these molecules. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)