An efficient ligand-free ferric chloride catalyzed synthesis of annulated 1,4-thiazine-3-one derivatives

A straight forward route for the synthesis of coumarin-, quinolone-annulated 1,4-thiazine-3-one derivatives has been achieved by using sodium sulfide as the sulfur source and ferric chloride as catalyst in a ligand-free condition. The synthetic procedure is simple, inexpensive, and affords the products in good yields. This methodology is also applicable to naphthalene and benzene systems.