8-Chloro-3- cyano – 2 – methylthio - 4-oxo - 4H – pyrimido [2,1-b][1,3]benzothiazole (3) on reaction in presence of dimethyl formamide and catalytic amount of anhydrous potassium with hydrazine hydrate / aryl hydrazine / heteryl hydrazine afforded 3-amino-8-chloro-4-oxo-(2H) / aryl/ heteryl-pyrazolo [3’,4’:4,5] pyrimido [2,1-b] [1,3] benzothiazoles (4a-i) in good yield. These newly synthesized compounds were evaluated for antibacterial activity.