Metal-Free Iodine-Catalyzed Synthesis of Fully Substituted Pyrazoles and Its Sulphenylation

A direct and metal-free access toward fully substituted pyrazoles and its sulphenylation has been established through an iodine-mediated three-component [3 + 2] annulation of β-ketonitrile (or pentane-2,4-dione), arylhydrazines, and aryl sulfonyl hydrazides. The reaction allows the formation of one C–S and two C–N bonds by the multiple bond cleavage including sulfur–oxygen, sulfur–nitrogen, and carbon–oxygen bonds. The method features low-cost and readily accessible substrates, bond-forming efficiency, and broad substrate scopes as well as simple one-pot operation, which makes this strategy highly attractive.