Synthesis of 2-Thioxo-1,3-benzothiazin-4-one by PPh 3 -Promoted Desulfurative [4 + 2] Annulation

An efficient construction of 2-thioxo-1,3-benzothiazin-4-ones has been developed via a PPh₃-promoted desulfurative [4 + 2] annulation between benzo[c][1,2]dithiol-3-ones and isothiocyanates. This strategy is characterized by its mild reaction conditions, operational simplicity, excellent yields, wide functional group tolerance, accessible scalability, and practical transformations.