Synthesis of α-fluorovinylphosphonates

A new general synthesis of α-fluorovinylphosphonates is provided by a Wadsworth-Emmons condensation of tetra-alkyl fluoromethylenebisphosphonates (1) with aldehydes and ketones. The reaction shows useful stereoselectivity favouring the less-hindered alkene product (3). Catalytic reduction of these alkenic products generally leads to α-fluoroalkylphosphonates (5), but hydrogenolysis of the carbon–fluorine bond was observed in the case of β-aryl-α-fluorovinylphosphonates. The free phosphonic acids are readily produced by de-esterification using halogenotrimethylsilanes.