A series of 2,1,3-and 1,2,4-benzothiadiazine derivatives were synthesized by alkylation via Mitsunobu reaction and evaluated for their antiviral activity against ADV, HHV-6, Cox-B5 and H-CMV. Most of them were active at micromolar level against one or more viral strains. All the molecules studied are poorly cytotoxic (maximum non toxic concentrations were >25µM), except one compound that presents a higher cytotoxicity (maximum non toxic concentration was 6 µM).