Spontaneous resolution and crystal structure of (2S)-2-(3-nitro­phen­yl)-3-phenyl-2,3,5,6-tetra­hydro-4H-1,3-thia­zin-4-one; crystal structure of rac-2-(4-nitro­phen­yl)-3-phenyl-2,3,5,6-tetra­hydro-4H-1,3-thia­zin-4-one

The crystal structures of isomeric rac-2-(4-nitro­phen­yl)-3-phenyl-2,3,5,6-tetra­hydro-4H-1,3-thia­zin-4-one (C(16)H(14)N(2)O(3)S) (1) and (2S)-2-(3-nitro­phen­yl)-3-phenyl-2,3,5,6-tetra­hydro-4H-1,3-thia­zin-4-one (C(16)H(14)N(2)O(3)S) (2) are reported here. While 1 crystallizes in a centrosymmetric space group, the crystal of 2 chosen for data collection has mol­ecules only with (2S) chirality. This is the result of spontaneous resolution during crystallization, as the synthesis produces a racemic mixture. A crystal with (2R) mol­ecules was also found in the same crystallization vial (structure factors available). The six-membered thia­zine ring in both 1 and 2 displays an envelope conformation with the S atom forming the flap. The aryl rings in both structures adopt an approximate V shape with angles between their planes of 46.97 (14)° in 1 and 58.37 (10)° in 2. In both structures, the mol­ecules form layers in the ab plane. Within such a layer in 1, one of the O atoms of the nitro­phenyl group accepts a C—H⋯O hydrogen bond from the CH group at position 5 of the thia­zine ring of a mol­ecule of opposite chirality, forming chains along the a-axis direction. Each of the thia­zine rings also participate in C—H⋯O bonds with the same carbon atom as above, resulting in chains along the b-axis direction, albeit of monochiral type. Adjacent layers are consolidated along the c-axis direction by pairs of parallel hydrogen bonds (C—H⋯O type) between the nitro­phenyl groups of enanti­omers. In 2, the two C—H⋯O hydrogen bonds contribute to chain formation along the b-axis direction. Weak edge-to-face inter­actions between the aryl groups of neighbouring mol­ecules in 1, and C—H⋯π inter­actions between a thia­zine ring CH group and a phenyl group of a neighboring mol­ecule in 2 are also observed.