AbstractA new synthetic approach to vinylphosphonates is presented. The reaction of diethyl benzoylphosphonate (1) with diethyl methoxycarbonyl‐methyl‐phosphonate (2) gives diethyl 2‐methoxycarbonyl‐l‐styrylphosphonate (3) as a mixture of geometrical isomers (Z‐3) and (E‐3) in the ratio of 83:17. In contrast, reaction of1with the heterocyclic phosphonate reagent, 2‐methoxycarbonyl‐methyl‐2‐oxo‐4,5‐dimethyl [1,3,2] dioxaphospholane (4) leads to a mixture of the isomers (Z‐3) and