An efficient route for synthesis of 5,6-diphenylimidazo-[2,1-b]thiazoles as antibacterial agents^†

The reaction of 4,5-diphenylimidazol-2-thione (1) with aromatic ketones 2a-i using the acidified acetic acid method afforded the 4,5-diphenyl(2-imidazolylthio)acetophenones 3a-h in good yields. While, the cyclized product 4i was obtained directly upon reaction of 1 with α-acetyl naphthalene. Compounds 3a-h were cyclized directly to the corresponding 3-aryl-5,6-diphenylimidazo[2,1-b]thiazoles (4a-c) and (4e-h). In the same manner the reaction of 1 with aliphatic and/or alicyclic ketones gave the 3-(4,5-diphenyl-2-imidazolylthio)acetone derivatives 5a-d, 2-(4,5-diphenylimidazolylthio)cycloalkanones 8a,d and the tricyclic compounds 9b-c respectively. The cyclized compounds 6a-d and 9a,d were obtained by cyclization of 5a-d and 8a,b respectively. Oxidation of 1 gives the corresponding bis(4,5-diphenyl-2-imidazolyl)-disulfide (10) in 90% yield. Some of the synthesized compounds were tested for antifungal and antibacterial activity.