A 1.53 N butyllithium solution (0.3 ml; 0.46 mmol) in hexane is added dropwise to a stirred solution of the ethyl phosphinate 3 (200 mg; 0.42 mmol) in THF (10 ml) at -78° C. under an atmosphere of argon. After 5 minutes benzyl bromide (0.06 ml; 0.51 mmol) is added dropwise to the deep-red reaction solution. After 2 hours the reaction solution is warmed to room temperature and after 15 hours diluted with ether. The solution is extracted with saturated aqueous ammonium chloride solution (2×20 ml). The organic phase is dried over Na2SO4 and evaporated under reduced pressure. The monoalkylated phosphinate 4 (187 mg, 79% of theory) is obtained after purification on silica gel using column chromatography (ethyl acetate/heptane=2/3).
