A sustainable and transition metal-free approach for C3 chalcogenation and chalcogenocyanation of imidazopyridines with KXCN (X = S or Se) has been developed under mild conditions. Importantly, this reaction was performed in the presence of catalytic iodine in aqueous medium, which afforded either chalcogenated or chalcogenocyanated imidazopyridines under temperature control. The current protocol featured a broad substrate scope, transition metal-free and organic solvent-free conditions, operational convenience, and gram-scale production.

A copper-mediated direct C3 amination of imidazopyridines has been disclosed under additive-free conditions in short reaction times. This methodology utilizes commercially available N-fluorobenzenesulfonimide (NFSI) as the amino source, which exhibits broad substrate scope and good functional group tolerance. The obtained C3-aminated imidazopyridines can undergo further desulfonylation transformations. Control experiments suggest that this reaction probably proceeds via a free-radical mechanism. Moreover, NFSI also shows potential application in C–H fluorination of imidazopyridines.

An efficient one pot, three component synthesis of C3 sulfonamidomethylated imidazopyridines has been disclosed utilizing methanol and DTBP as the major and minor methylene source, respectively.

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An iron-catalyzed C–H sulfonylmethylation of indoles in water–PEG400 has been developed using p-toluenesulfonylmethyl isocyanide. This protocol enables direct regioselective construction of Csp2–Csp3 bond at the C3 position of indoles with a broad range of substrate compatibility in moderate to good yields, which is cost-effective and environmentally friendly.