α,α-Difluoro-β-iminophosphonates, an alternative strategy towards the synthesis of α,α-difluoro-β-aminophosphonate derivatives

Abstract

α,α-Difluoromethylenephosphonates are generally known as stable natural phosphate mimics with significantly improved biological activities. A number of α,α-difluoroalkylphosphonates have already been found to be important enzyme inhibitors. Herein, we report an alternative strategy towards the synthesis of α,α-difluoromethylene-β-aminophosphonate derivatives. A small library of N-substituted α,α-difluoro-β-aminophosphonates was designed and described via NMR study. The protocol began with the condensation of β-ketophosphonates with a series of primary amines. The key step of the synthesis is an electrophilic fluorination, mediated by Selectfluor®, of the mixture of β-enamino/β-iminophosphonates leading to α,α-difluoro-β-iminophosphonates followed by reduction. The title compounds may behave as convenient building blocks for further more advanced modification.