Iron(iii) chloride-promoted cyclization of α,β-alkynic tosylhydrazones with diselenides: synthesis of 4-(arylselanyl)-1 H -pyrazoles

A highly efficient iron(iii) chloride-promoted cyclization between alpha,beta-alkynic tosylhydrazones and diselenides to form a 4-(arylselanyl)-1H-pyrazole skeleton is studied. This reaction forms C-N and C-Se bonds in one step by utilizing inexpensive iron(iii) chloride instead of expensive transition metal additives. This strategy features easily synthesized substrates, mild reaction conditions and high tolerance to functional groups.