Abstract
Background: While C-S bonds coupling is playing a crucial role in the syntheses of many biologically active substances, the well concerned C-H functionalization reactions have been barely employed yet in construction of such sulfur compounds.
Objective: The primary objective of this study was to expand the application of copper, a cheap metal, to catalyze C-S bond construction reactions of indoles.
Methods: We chose copper compounds of various oxidant states as catalysts. Substituted indoles were picked as substrates, and disulfides as sulfur source. The variants of catalyst, solvent and reaction temperature were screened to optimize the reaction condition. After that, we explored the scope of diversely substituted indoles and disulfides substrates of the reaction.
Results: The reactions were all smoothly performed to provide corresponding products in good yields. The main product is tunable between C3-sulfenylindoles and C2,3-sulfenylindoles according to the amount of disulfides. C3-sulfenylindoles were synthesized in 85 to 99% yields. C2,3-sulfenylindoles were also fruitfully obtained in from 66 to 98% yields.
Conclusion: A facile and efficient method for sulfenylation of indole, which employed CuI as catalyst, to give C3- and C2,3- sulfenylindoles, was presented. Our methodology features easy operation, excellent yields and cheapness of catalyst.
Keywords: C-H activation, copper, cross-coupling, heterocycles, sulfenylation, indoles.
Graphical Abstract
Call for Papers in Thematic Issues
Catalytic C-H bond activation as a tool for functionalization of heterocycles
The major topic is the functionalization of heterocycles through catalyzed C-H bond activation. The strategies based on C-H activation not only provide straightforward formation of C-C or C-X bonds but, more importantly, allow for the avoidance of pre-functionalization of one or two of the cross-coupling partners. The beneficial impact of ...read more
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