m-Chloroperbenzoic acid → 5-chloro-2-methyl-3-(piperidin-4-yl-sulfinyl)-1H-indole

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Reaction Steps

Metachloroperbenzoic acid (2.79 g) is added in portions to a solution of 5-chloro-2-methyl-3-(piperidin-4-ylthio)-1H-indole (3 g, prepared in Example 18) in dichloromethane (25 ml) at -40° C. After 4 hours at room temperature, the insoluble material is filtered off. The filtrate is washed with sodium hydroxide and then with water. The aqueous phases are extracted with ether and then with ethyl acetate. The organic phases are combined, dried over magnesium sulfate and concentrated. The oily residue obtained is chromatographed on silica gel (eluent: CH2Cl2 /MeOH/NH4OH:90/10/1) to give 5-chloro-2-methyl-3-(piperidin-4-yl-sulfinyl)-1H-indole in the form of an oil, which crystallizes on the addition of ether (0.4 g).

Provenance & Evidence