0.13 g of sodium hydride as an 80% dispersion in oil was added in portions, with stirring, to a solution of 1 g of 5-chloro-3-cyclohexyl-1,3-dihydro-2H-benzimidazol-2-one in 10 ml of DMF at room temperature; 1.1 g of 2-methoxy-4-nitrobenzenesulfonyl chloride were then introduced and the reaction medium was stirred at room temperature for 4 hours. The solvent was then evaporated off under vacuum and the residue obtained was taken up with water. It was then extracted with DCM, washed with water and then dried over sodium sulfate and the solvent was evaporated off to dryness. The residue obtained was chromatographed on silica using a DCM/AcOEt mixture (95/5; v/v) as the eluent to give the expected product in the form of a slightly yellow solid, which crystallized from absolute EtOH. m=1.52 g. M.p.=185° C.
