2,3-Diphenyl-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-one

The six-membered thiazine ring in the title compound, C16H15NOS, adopts a half-chair conformation, with the S atom forming the back of the chair. The base of the chair has a slight twist reflected in the r.m.s. deviation (0.0756 Å) of those five atoms from the plane defined by them. The phenyl substituents are almost perpendicular to each other [dihedral angle 87.06 (9)°]. In the crystal, molecules are linked into chains parallel to the c axis through C—H⋯O interactions.

The six-membered thiazine ring in the title compound, C 16 H 15 NOS, adopts a half-chair conformation, with the S atom forming the back of the chair. The base of the chair has a slight twist reflected in the r.m.s. deviation (0.0756 Å ) of those five atoms from the plane defined by them. The phenyl substituents are almost perpendicular to each other [dihedral angle 87. 06 (9) ]. In the crystal, molecules are linked into chains parallel to the c axis through C-HÁ Á ÁO interactions.

Experimental
A two-necked 25 ml roundbottom flask was oven-dried, cooled under N 2 , and charged with a stir bar and N-benzylideneaniline (1.087 g, 6 mmol). Tetrahydrofuran (2.3 ml) was added, the solid dissolved, and the solution was stirred.
The product eluted with 60-100% EtOAc/hexanes and was concentrated in vacuo to pale yellow viscous oil (1.3720 g).
Crystals for X-ray crystallography were grown by dissolving the solid in ethanol, adding some water, and then allowing slow evaporation to occur. After crystals grew, the supernatant was decanted off, and the crystals were rinsed twice with 95% ethanol.

Refinement
The C-bound H atoms were geometrically placed with C-H = 0.93-0.97 Å, and refined as riding with U iso (H) = 1.2U eq (C).

Figure 1
ORTEP view of the title comound. Displacement ellipsoids were drawn at the 50% probability level.   Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.