2,3-Diphenyl-2,3-dihydro-4H-1,3-benzothiazin-4-one

In the title compound, C20H15NOS, the dihedral angle between the phenyl rings is 74.25 (6)°. The six-membered 1,3-thiazine ring has an envelope conformation with the C atom at the 2-position forming the flap. The crystal structure features weak C—H⋯O interactions, which lead to the formation of a tape motif along [110].

We acknowledge NSF funding (CHEM-0131112) for the X-ray diffractometer, and are thankful to Dr John Tierney for intellectual contributions and to Euticals Inc. for the gift of T3P in 2-methyltetrahydrofuran. RVB, DJC, and ASC acknowledge summer internship support from SP Controls Inc.

Experimental
A two-necked 25 ml roundbottom flask was oven-dried, cooled under N 2 , and charged with a stir bar and N-benzylideneaniline (1.02 g, 6 mmol). Tetrahydrofuran (2.3 ml) was added, the solid dissolved, and the solution was stirred.

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) = 1.2 U eq (C).

Figure 1
ORTEP view of the title comound. Thermal ellipsoids are drawn at 50% probability.  Crystal packing. C-H···O interactions are shown as dashed lines.

2,3-Diphenyl-2,3-dihydro-4H-1,3-benzothiazin-4-one
Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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.

Experimental
A two-necked 25 ml roundbottom flask was oven-dried, cooled under N 2 , and charged with a stir bar and N-benzylideneaniline (1.02 g, 6 mmol). Tetrahydrofuran (2.3 ml) was added, the solid dissolved, and the solution was stirred.

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) = 1.2 U eq (C).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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.