Nano CoFe2O4 is found to be efficient catalyst for synthesis of 1-substituted 1H-1, 2, 3, 4- tetrazoles under solvent-free conditions. The significant advantages of this methodology are high yields, elimination of dangerous and harmful hydrazoic acid and simple work-up
[El-Ahl, Abdel-Aziz S.; Amer, Fatty A.; Elbeheery, Akram H. Phosphorus, Sulfur and Silicon and the Related Elements, 2011 , vol. 186, # 11 p. 2226 - 2235]