Electrochemical Sulfenylation of Indoles with Disulfides Mediated by Potassium Iodide

Abstract

A novel electrochemical system for sulfenylation of indoles with disulfides to generate 3-sulfenylindoles via C-S bond formation mediated by potassium iodide at a low potential was developed. Iodine was electrogenerated from iodide ions at a graphite anode and showed a high catalytic activity for the electrochemical sulfenylation reactions. A variety of aromatic, heteroaromatic and aliphatic disulfides could react with 2-methlyindole to synthesize the corresponding 3-sulfenylindoles in good to excellent yields. In addition, protected and unprotected indoles with various groups, especially electron-donating groups, also performed well in the sulfenylation reactions. The transformation, which proceeded through the redox of iodine and the generation of intermediate 3-iodoindole, provided an efficient and environmentally benign protocol for the synthesis of 3-sulfenylindoles under mild conditions.

Recent Advances in the Electrochemical Synthesis and Functionalization of Indole Derivatives

“…The heterolysis of RSeI then generates the strong electrophile RSe + which is prone to selenate indole. Other electrochemical indole functionalizations including halogenation, thio‐ and selenocyanation, sulfenylation and sulfonylation have also been developed recently.…”

Versatile Electrochemical Oxidative C(sp2)−H Bond Selenylation of Resveratrol

“…Recently, a broad study of the mechanism involved in iodine catalysis was carried out by von der Heiden and Breugst, [53] and it is known that the use of acetonitrile in iodinemediated reactions is successful, being the target of several electrosynthetic reactions. [54][55][56][57] In order to investigate the role of NaI, and considering that iodine (I 2 ) can be obtained from iodide ions (I -) by anodic oxidation and act as a redox mediator in electrosynthesis, the reactions illustrated in Scheme 4B -E were performed. Experiment 4B provided the product 3 a in 70 % conversion, suggesting a possible mechanistic route via the phenylselenyl halide intermediate.…”

Recent Advances in Electrochemical Oxidative Cross-Coupling for the Construction of C–S Bonds

“…In 2018, Li et al developed a potassium iodide mediated electrochemical sulfenylation of indoles with disulfides (Scheme 21). 34 A series of 3-sulfenylated indole adducts could be obtained in good to excellent yields.…”