Diethyl 1-fluoro-1-phenylsulfonylmethanephosphonate (1) in the presence of cesium carbonate undergoes efficient 1,4-addition to Michael acceptors having terminal double bonds such as α,β-unsaturated ketones, esters, sulfones, sulfoxides, and phosphonates to yield the corresponding adducts in good to excellent yields. In the presence of sodium hydride, 1 reacts with α,β-enones to provide γ-fluoro-γ-phenylsulfonylenol phosphates arising from 1,4-addition followed by phosphonate to phosphate rearrangement.