A new series of N-(5-acetyl-4-methyl-3-(substituted phenyl)-thiazol-2-ylidene)-4-methyl (substituted) benzamides 2a-o was synthesized by heterocyclization of the corresponding 1- substituted benzoyl-3-arylthioureas 1a-o with 3-chloropentane-2,4-dione under microwave irradiation in the absence of any solvent or catalyst. All synthesized compounds have been evaluated for their antiviral activity against the replication of HIV-1 and HIV-2 activity in MT-4. However, compounds 2j and 2n showed activity against HIV-2 with EC50 of 2.44 μg ml-1 and 1.89 μg ml-1 (CC50 of 60.68 μg ml-1 and 49.38 μg ml-1), respectively, resulting in a selectivity index of 25 and 26. The results suggest that these compounds can be considered as a new lead in the development of antiviral agents.