The indole moiety is probably the most common heterocycle in natural and pharmaceutical agents.1 Substituted indole derivatives are considered “privileged structures” as they tend to combine with many receptors. Since the development of synthetic chemistry, the functionalization and synthesis of indole derivatives has aroused much interest from synthetic organic chemists, and numerous effective methods for preparing indoles have been developed. However, most of these methods require an equivalent oxidant or an excess of catalyst. In addition, indole derivatives containing sulfonyl groups are widely found in natural products and drug molecules. synthetic 3-arylsulfonyl-1H-indoles have served as valid HIV-1 Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs) and 5-HT6 receptor ligands useful in the treatment of CNS disorders. Unlike azo compounds that are widely used in the dyestuff industry, many marketed drugs, including isoniazid,mildronate, hydralazine, and benserazide, contain hydrazine functional groups. The hydrazine skeleton also displays a variety of bio-activities, such as anti-schistosomal, anti-cancer, anti-bacterial, anti-inflammatory, and anti-oxidant activities. Therefore, introducing this group into the indole ring presents an attractive research direction, but only few chemists have undertaken such activity.

Electrochemical organic synthesis technology is to realize redox reaction by transferring charge between anode and cathode at the interface of electrode/solution, which replaces the role of traditional oxidant or reductant. It can avoid the troubles of by-product post-treatment and environmental pollution caused by a large number of chemical oxidants in traditional organic reactions. It has the characteristics of simplicity, high efficiency, mild conditions and good economy. Under mild electrochemical conditions, we designed and synthesized a series of sulfonyl hydrazinyl indoles which have not been reported in literature. The selective sulfonylation and hydrazination of indole with sulfonyl hydrazide were realized by using constant current instead of exogenous oxidant. The problem of desulfurization or excessive oxidation of sulfonyl group was effectively avoided and a series of sulfonyl hydrazide indole compounds which could not be obtained by traditional methods were obtained. Comparing with this, it is more green and environmental protection.

The in vitro cytotoxicities of all compounds against four cancer cell lines were screened by using the MTT assay. The results showed that most of the compounds had good antitumor activity. The IC₅₀ values of compound 3ae for T-24 and HepG-2 were 12.4 ± 1.4 and 15.3 ± 0.9 μM, respectively. Moreover, the preliminary analysis of the mechanism of action studies revealed that the compound 3ae inhibited cell migration and tubulin polymerization in T-24 cells, thereby leading to cell cycle apoptosis.