3 g (8.62 mmol) of tetrabutylammonium iodide, 3.02 g (20.4 mmol) of potassium carbonate and then 2.36 ml (20.4 mmol) of 2-chloromethyl-3-chloro-1-propene are successively introduced into a solution of 2.5 g (8.16 mmol) of readily accessible 1-{4-hydroxy-3-[(phenylsulfonyl)methyl]phenyl}ethanone in 150 ml of N,N-dimethylformamide. The solution is stirred at ambient temperature for 20 hours and then water, ether and 1N hydrochloric acid are added, the reaction medium being cooled to 0° C. using a water bath and ice. The solid obtained by filtration is discarded, the phases are separated by settling and then the aqueous phase is extracted several times with ether. The combined organic phases are washed several times with an aqueous solution and then with brine. After drying and concentration under vacuum, the crude reaction product is purified by chromatography on silica gel (ethyl acetate/heptane 40/60) to provide 1.63 g (50%) of methyl 4-{[2-(chloromethyl)-2-propenyl]oxy}-3-[(phenyl-sulfonyl)methyl]benzoate in the form of a white solid; M.p.=92–93° C. (M.p. denotes the melting point of the compounds).
