Abstract
A series of 1,2,4-triazolopyridines have been prepared by oxidative intramolecular cyclization of heterocyclic hydrazones with [bis(trifluroacetoxy)iodo]benzene. General applicability of this simple transformation was confirmed by synthesis of 1,2,4-triazolo[4,3-a]pyridine. The advantages of this protocol are the nontoxicity of catalyst and shorter reaction time to obtain good preparative yield.
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ACKNOWLEDGMENT
The author is thankful to Indian Institute of Technology Mumbai, for providing the 1H NMR facility.
Notes
a Reagents and reaction conditions: 2-hydrazinopyridine (10 mmol), aldehydes (10 mmol); solvent: ethanol; temperature: reflux temperature; time: 20 min.
b Starting compound 2-hydrazinopyridine prepared by the standard reported procedure.
c Isolated yield.
d Compounds were confirmed by physical constants.
a Isolated yield after crystallization in benzene.
Note. Catalyst: [bis(trifluroacetoxy)iodo]benzene (11 mmol equivalent); time: 10 min.
a Reagents and reaction conditions: Hydrazones (10 mmol), [bis-(trifluroacetoxy)iodo]benzene (11 mmol); solvent: anhydrous dichloromethane; temperature: room temperature; time: 10 min.
b Isolated yield after crystallization and structure were confirmed by 1H NMR spectra and physical constants.