The one pot synthesis of 9-chloro-3-cyano-8-fluoro-2-methylthio-4-oxo-4H-pyrimido [2, 1-b] [1, 3] benzothiazole (3) and its 2-substituted derivatives is convenient over traditional route of synthesis of this compound. This has been prepared by the reaction of 2-amino-7chloro-6-fluoro benzothiazole (1) with ethyl-2-cyano-3, 3-bismethyl thioacrylate (2) in the presence of dimethyl formamide and anhydrous potassium carbonate. Susceptibility of compound (3), towards condensation with different reagents like aryl amines, heteryl amines and compounds containing active methylene groups has been investigated. These newly synthesized compounds were evaluated for their in-vitro anticancer activity towards human cancer cell lines derived from various cancer types