Potassium Persulfate Mediated Chemodivergent C-3 Functionalization of 2-Indazoles with DMSO as C Source.

A facile, efficient, and transition-metal-free chemodivergent C-3 functionalization of 2-indazoles was developed under aerobic conditions using carboxylic acid and DMSO as the combined source of the carboxylic acid ester group and DMSO as the formylating agent. A series of formylated indazoles and carboxylic acid esters of indazole derivatives were produced in moderate to excellent yields. The mechanistic studies suggest that the reactions probably proceed through a radical pathway.