Water → Diethyl 4-methyl-2oxa-pent-4-enylphosphonate

Diethyl hydroxymethylphosphonate (3 g, 17.8 mmol, 1 eq) is dissolved in 50 ml of THF to which sodium hydride (0.43 g, 17.8 mmol, 1 eq) is added. 1-chloro-2-methylpropene (1.62 g, 17.8 mmol, 1 eq) is then added. After one hour under magnetic stirring, at ambient temperature and in a nitrogen atmosphere, hydrolysis is performed with 100 ml of water. Extraction is performed with ether (3×50 ml). The organic phases are collected, washed with 100 ml of a saturated sodium chloride solution and dried on sodium sulphate. After evaporation of the solvent, the residual oil obtained is purified by silica gel chromatography (Eluent=ethyl acetate).