Crystal structures of 2-(4-nitrophenyl)-3-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-one and 2-(2-nitrophenyl)-3-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-one

The crystal structures are reported of the isomeric compounds 2-(4-nitrophen-y1)-3-pheny1-2,3-dihydro-4H-1,3-benzothiazin-4-one, (I), and 2-(2-nitrophenyl)-3-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-one, (II), both C₂₀H₁₄N₂O₃S, being the para-nitro and ortho-nitro forms, respectively, the meta-form of which is known [Yennawar et al (2013). Acta Cryst. E69, o1679]. The six-membered thiazone ring fused with a benzene ring displays a screw-boat conformation with a total puckering amplitude of 0.627 (1) Å in (I), and a near screw-boat conformation with a total puckering amplitude of 0.600 (1) Å in (II). The dihedral angles between the planes of the substituent nitrophenyl and phenyl and rings with the benzene ring of the parent benzothiazone moiety are 75.93 (5) and 82.61 (5)° [in (I)], and 76.79 (6) and 71.66 (6)° [in (II)]. Weak intermolecular C - H⋯O hydrogen-bonding interactions between aromatic H-atom donors and both a nitro-O atom and a thiazone O-atom acceptor in (I) and a thiazone O atom in (II) are present, forming in (I) a centrosymmetric 22-membered cyclic dimer which is extended through a similar inversion-related 14-membered cyclic hydrogen-bonding association into a zigzag chain structure extending along c. In (II), a single intermolecular C - H⋯O hydrogen bond gives a chain structure extending along b. In addition, weak C - H⋯π interactions are present in both structures [minimum C⋯ring-centroid separations = 3.630 (2) and 3.581 (2) Å, respectively].