Tirapazamine can be obtained by several related ways: 1) By condensation of benzofurazan (I) with cyanamide disodium salt (II) in hot methanol/water. 2) The condensation of 2-nitroaniline (III) with cyanamide (IV) by heating at 100 C gives 3-amino-1,2,4-bezotriazine 1-oxide (V), which is then oxidized with 30% aqueous H2O2 in hot acetic acid. 3) The reaction of 3-hydroxy-1,2,4-benzotriazine 1-oxide (VI) with refluxing POCl3 and dimethylaniline gives 3-chloro-1,2,4-benzotriazine 1-oxide (VII), which by reaction with dry ammonia in ethanol is converted into the corresponding amino derivative (V), already obtained.