Crystal structure of 2,3-diphenyl-2,3-dihydro-4H-1,3-benzothiazin-4-one 1-oxide

In the racemic title compound, C₂₀H₁₅NO₂S, 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 - H⋯O hydrogen-bonding interactions.