1-(5,5-Dioxido-10H-phenothiazin-10-yl)ethanone

In the title compound, C14H11NO3S, the six-membered thiazine ring fused to two benzene rings adopts a distorted boat conformation. The dihedral angle between the mean planes of the two benzene rings is 45.8 (1)°. The crystal packing is stabilized by weak intermolecular C—H⋯O interactions.

In the title compound, C 14 H 11 NO 3 S, the six-membered thiazine ring fused to two benzene rings adopts a distorted boat conformation. The dihedral angle between the mean planes of the two benzene rings is 45.8 (1) . The crystal packing is stabilized by weak intermolecular C-HÁ Á ÁO interactions.
MSS thanks the University of Mysore for the research facilities and R. L. Fine Chem, Bangalore, India, for the gift sample. JPJ acknowledges the NSF-MRI program (grant No. CHE1039027) for funds to purchase the X-ray diffractometer.

Comment
Phenothiazine is a well known heterocycle. The phenothiazine structure occurs in many synthetic dyes, electroluminescent materials (Miller et al., 1999) and drugs, especially various antipsychotic drugs, e.g. chlorpromazine and antihistaminic drugs, e.g. promethazine (Wermuth, 2003). Recently, researchers have found some new applications for phenothiazine derivatives in medicine related to antitubercular (Wang et al., 2008) and antitumor activities (Lam et al., 2001). The title compound has been used in the synthesis of oxomemazine, an antihistamine and anticholinergic drug of the phenothiazine chemical class used for the treatment of coughs. The crystal structures of dioxopromethazinium picrate (Harrison et al., 2007) and 1-(10H-phenothiazin-2-yl)ethanone (Jasinski et al., 2011) have been reported. In view of the importance of phenothiazines, this paper reports the crystal structure of the title compound, C 14 H 11 NO 3 S.

Experimental
The title compound was obtained as a gift sample from RL Fine Chem, Bangalore, India. X-ray quality crystals were obtained by slow evaporation of solution of a 1:1 mixture of acetone:ethanol (m.p.: 495 K).

Refinement
All of the H atoms were placed in their calculated positions and then refined using the riding model with Atom-H lengths of 0.95Å (CH), or 0.98Å (CH 3 ). Isotropic displacement parameters for these atoms were set to 1.19-1.21 (CH) or 1.49 (CH 3 ) times U eq of the parent atom.

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