Tetraethyl methylenebisphosphonate (1.44 g, 5.0 mmol) in THF (1 mL) was added to a slurry of 80% sodium hydride (150 mg, 5.0 mmol) in THF (4 mL) at 0° C. The reaction was warmed to room temperature and stirred until all of the hydride was consumed. A solution of N-butyl-2-chloroacetamide (0.75 g, 5.0 mmol) in THF (1 ml) and potassium iodide (100 mg) were then added. The reaction mixture was then heated at 50° C. for 18 hours, during which time sodium chloride precipitated. Additional sodium hydride (20 mg) was added, and the reaction mixture was heated an additional 4 hours. After cooling, the mixture was poured into 1N HCl (10 mL) and diethyl ether (50 mL) was added. The diethyl ether layer was further extracted with water (3×10 mL). The combined aqueous fractions were extracted with dichloromethane (4×25 mL). The combined extracts were dried (Na2SO4) and concentrated to give the title compound (1.40 g, 70%) as an oil.
