A series of new 2-(2-chloro-substitutedquinilino-3-yl)-4-(2’-phenylthiazol-5’-yl)-2,3-dihydro-1,5-benzothiazepines (4a-f) have been prepared by carrying cyclocondensation of new 3-(2-chloro-substitutedquinolin-3-yl)-1-(4-metyl-2- phenylthiazol-5-yl)prop-2-en-1-ones (3a-f) and 2-aminothio phenol in DMF. Intermediate chalcones were obtained from the interaction of 2-chloro-substitutedquinoline-3-carbaldehyde (1) and 1-(4-methyl-2-phenylthiazol-5- yl)ethanone (2) in ethanol, using claisen condensation. The synthesized 1,5-benzothiazepines 4a, 4c, 4d and 4f have been screened for their antibacterial activity against Staphylococcus aureus, Bacillus subtilis and Escherichia coli