Chemoselective Reaction of Benzoylisothiocyanates with Hydroxyl Group of Salicylamide: a New and Convenient Entry Into 2-Aryl-4H-benzo[e][1,3]oxazin-4-ones

Abstract The reactions of benzoylisothiocyanates with salicylamide in pyridine-xylene solution occurs chemoselectively at the hydroxyl group of the salicylamide to afford the corresponding O-benzoyl derivatives. The latter products, on prolonged heating in pyridine-xylene solution, undergo cyclodehydration to give 2-aryl-4H-benzo[e][1,3]oxazin-4-ones in good yields. These compounds could also be synthesized by a direct one-pot reaction of benzoylisothiocyanates with salicylamide by slow addition of benzoylisothiocyanates into a solution of salicylamide in xylene-pyridine solution under reflux. The products have been characterized on the basis of satisfactory analytical and spectral data.