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A C3-selective sulfenylation of free (N-H) indoles can be achievedunder mild conditions using disulfide or thiols sulfurate coupling of free(N-H) indoles under alkaline conditions.First, sulfenylation of indole was initially examined usingcommercially available2,2’-dithiosalicylic acid(DTSA) and1H-indole.The transformation was further investigated, and finally the optimumconditions were obtained. This simple process is compatible with diversefunctionalized indoles and generally provides the desired products ingood yields. A series of functional groups such as methoxy, bromo, fluoro,hydroxyl, and methyl, at C5or C6position of1H-indole wereinvestigated under this process.10sulfenylation products were obtained,and6of them are new products.Second, the sulfenylation of diverse1H-indole derivatives with thiolswas also investigated. A series of functional groups such as methoxy, bromo, fluoro, hydroxyl, and methyl, at C5or C6position of1H-indolewere studied, which result in18sulfenylation products and10of themare new substances.Finally, based on these experimental results and other similar studiesreported, a general mechanism for a C3-selective sulfenylation of free(N-H) indoles by disulfides was proposed, and an electrophilic additionmechanism was suggested. A similar mechanism was also proposed forthe sulfenylation of (N-H) indole with thiols.The structures of all products were purified by columnchromatography, and characterized by NMR、HRMS、IR、XRD.
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