Solvent‐Free Dehydrogenative C‒H Chalcogenations of Pyrazolones Using Mechanochemistry

A mechanochemical cross‐dehydrogenative coupling reaction of pyrazolones with thiols using ball milling is described. Benzeneselenol and dichalcogenide substrates are also compatible under mild reaction conditions, yielding up to 99%. Notable features of this reaction include its metal‐ and solvent‐free, wide substrate scope and good functional group tolerance. Preliminary mechanistic investigations suggest that a radical pathway is likely involved in this C‒H chalcogenation reaction