Solvent-free preparation of arylaminotetrazole derivatives using aluminum(III) hydrogensulfate as an effective catalyst

An efficient and simple method for the preparation of 5-arylamino-1H-tetrazole and 1-aryl-5-amino-1H-tetrazole derivatives is reported using aluminum(III) hydrogensulfate (Al(HSO4)3) as an effective heterogeneous catalyst from secondary arylcyanamides. Generally, when the substitution in arylcyanamide is strongly electron-withdrawing the position of equilibrium would shift toward the isomer of 1-aryl-5-amino-1H-tetrazole (B) and as the electron-donating of substituent increased, the position of equilibrium is shifted toward the isomer of 5-arylamino-1H-tetrazole (A). The present methodology offers several advantages, such as excellent yields, short reaction times, easy work-up and greener conditions.