AgNO3 facilitated the intramolecular ring closure of o-(1-alkynyl)benzenesulfonamides via a regioselective C-N bond forming reaction leading to the formation of 3-substituted benzothiazine derivatives. A number of compounds were prepared in good yields by using this inexpensive and safe methodology. All the compounds synthesized were evaluated for their cyclooxygenase (COX) inhibiting properties in vitro. A number of compounds that do not contain an enolic hydroxyl group showed selectivities toward COX-2 over COX-1 inhibition. This was further supported by the predictive binding mode of two compounds with COX-1 and -2 proteins through molecular docking studies.