ClC1C=CC=C(C(OO)=[O:9])C=1.[CH3:12][O:13][C:14]1[CH:36]=[CH:35][C:17]2[NH:18][C:19]([S:21][CH2:22][C:23]3[N:28]=[C:27]([N:29]4[CH2:34][CH2:33][CH2:32][CH2:31][CH2:30]4)[CH:26]=[CH:25][N:24]=3)=[N:20][C:16]=2[CH:15]=1.N>ClCCl>[CH3:12][O:13][C:14]1[CH:36]=[CH:35][C:17]2[NH:18][C:19]([S:21]([CH2:22][C:23]3[N:28]=[C:27]([N:29]4[CH2:34][CH2:33][CH2:32][CH2:31][CH2:30]4)[CH:26]=[CH:25][N:24]=3)=[O:9])=[N:20][C:16]=2[CH:15]=1A solution of m-chloroperbenzoic acid (1.69 g) in dichloromethane (25 ml) was added to a stirred solution of 5-methoxy-2-[4-piperidino-2-pyrimidinylmethylthio]-(1H) benzimidazole (3.48 g) in dichloromethane (75 ml) cooled to between -30° and -35°. After 1.5 hours at -20° a further quantity of m-chloroperbenzoic acid (0.34 g) was added. After a further 30 minutes ammonia was passed through the reaction mixture and the precipitated solid filtered off. The filtrate was washed with aqueous sodium carbonate, which was back washed with chloroform. The combined organic phases were dried (K2CO3) stripped and the residue purified by column chromatography (silica gel, 2% MeOH-NH3 /CHCl3) to give 5-methoxy-2-(4-piperidino-2-pyrimidinylmethylsulphinyl)-(1H)-benzimidazole (3.28 g) as an oil.
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