Various methods have been reported for the synthesis of 5-substituted 1H-tetrazole, most of which are based on the addition of sodium azide (NaN 3 ) or trimethylsilyl azide (TMSN 3 ) to nitrile group. The reactions were carried out by using catalysts such as copper triflates 14a , CdCl 2 , 14b Fe(OAc) 2 14c zinc(II) salts, 14d Bronsted acid catalyst, 14e various Lewis acid catalysts such as AlCl 3 15 , BF 3 –OEt 2 , 16 FeCl 3 17 , TBAF, 18 and by using some ...