Environmentally benign electrochemically enabled chemoselective sulfonylation and hydrazination of C2,C3-unsubstituted indoles with arylsulfonyl hydrazide in the presence of ammonium bromide as a redox catalyst and electrolyte have been demonstrated in this work. Under mild electro-oxidation conditions, a series of indole hydrazination products with pharmacological activity were obtained. In vitro, the hydrazination products exhibited a better anti-cancer activity compared with the diazotization products. Further mechanistic studies showed that compound 3ae inhibits cell migration and tubulin aggregation in T-24 cells, thereby leading to cell apoptosis.

Herein, a transition metal-free and efficient cascade reaction of ynones with 2-methylbenzimidazoles under mild conditions has been revealed. This cascade reaction involved a Michael addition/intramolecular cycloaddition/dehydration and provided the desired benzo[4,5]imidazo[1,2-a]pyridines in moderate to good yield. Furthermore, three benzo[4,5]imidazo[1,2-a]pyridines (3d, 3i, and 3q) exhibited good activities against Hep-G2 (human liver cancer), T-24 (human bladder cancer cell), and SK-OV-3 (human ovarian cancer) cell lines with IC₅₀ values in the range of 8.05–10.67 μmol L⁻¹. To investigate the mechanism of the effective inhibition of cell growth, further studies, including cell cycle analysis, apoptosis ratio detection, measurement of Ca²⁺ generation, ROS, mitochondrial membrane potential assay, and caspase-3/9 activation, were carried out on compound 3i.