A series of 11 novel 3‐aryl‐2‐phenyl‐2,3‐dihydro‐4H‐1,3‐benzothiazin‐4‐ones was prepared at room temperature by T3P‐mediated cyclization of N‐aryl‐C‐phenyl imines with thiosalicylic acid. This provides simple and ready access to N‐aryl compounds in this family, which have been generally difficult to prepare.

This review updates an earlier review published in 1996 by Ryabukhin, Korzhavina, and Suzdalev, which covered the literature through 1994. It deals with the synthesis and reactivity of 1,3-thiazin-4-ones and their derivatives. These include reduced compounds, 2-imino or 2-amino compounds, compounds with fused arenes or heterocycles, bridged compounds, and compounds combining various of these attributes.

In the racemic title compound, C 20 H 15 NO 2 S, the planes of the two phenyl substituents form dihedral angles of 48.97 (15) and 69.26 (15) with that of the fused benzene ring of the parent benzothiazine ring, while the heterocyclic thiazine ring exhibits a screw-boat pucker. The O atom on the S atom of the ring is pseudo-axial on the thiazine ring and trans to the 2-phenyl group. In the crystal, molecules are arranged in layers in the ac plane, the layers being linked across b through intermolecular C-HÁ Á ÁO hydrogen-bonding interactions.