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.
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.