Abstract2‐Aryl‐4‐thioxo‐1,3‐benzothiazines react with thiocarbohydrazide to give the new mesoionic compounds an‐hydro 1‐amino‐5‐aryl‐2‐mercapto‐1,3,4‐triazolo[3,2‐c]quinazolin‐4‐ium hydroxides. These compounds react with methyl iodide, aldehydes and phenacyl bromides to give 1‐amino‐5‐aryl‐2‐methylthio‐1,3,4‐triazolo‐[3,2‐c]quinazolin‐4‐ium iodides, 4‐arylidenamino‐3‐(o‐aroylamino)phenyl‐1H‐1,2,4‐triazolin‐5‐thiones and 3‐(o‐aroylamino)phenyl‐6‐aryl‐7H‐1,2,4‐triazolo[3,4‐b]‐1,3,4‐thiadiazines, respectively. These latter compounds by sequential treatment with methyl trifluoromethanesulphonate and triethylamine le