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.