9-chloro-3-cyano-8-fluoro-2-methylthio-4-oxo-4-H-pyrimido[2,1-b] [1,3] benzothiazole(3) on reaction in presence of dimethyl formamide (DMF) and catalytic amount of anhydrous potassium carbonate with hydrazine hydrate / aryl hydrazine/heteryl hydrazine afforded 3- amino -9- chloro-8- fluoro -4- oxo- (2H)/aryl/heteryl- pyrazolo [3’, 4’ : 4, 5] pyrimido [2,1-b] [1,3] benzothiazoles (4a-g) in good yield. These newly synthesized compounds were evaluated for their in-vitro anti-cancer activity towards human cancer cell lines derived from various cancer types.