The reaction of phosphates 1 and 5 and thiophosphates 3 and 7 gave the olefins 2 and 6 with 0.8–1.6 mol eq of Lawesson's reagent in xylene at reflux. Compounds 1, 3, 8, 5 and 7 gave 2 and 6 in better yields with a small amount of AgOTf (0.1–0.3 mol eq) even in toluene at reflux.