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.