10-Acetyl-10H-phenothiazine 5-oxide

In the title compound, C14H11NO2S, the sulfoxide O atom is disordered over two sites with occupancies of 0.886 (4) and 0.114 (4), reflecting a partial inversion of the lone pair at the tetrahedral S-atom site. In the crystal, a supramolecular arrangement arises from weak intermolecular C—H⋯O hydrogen bonds. π–π contacts between the aromatic rings of symmetry-related molecules [centroid–centroid distances = 3.7547 (15) and 3.9577 (15) Å] in parallel accumulation further stabilize the crystal structure.

In the title compound, C 14 H 11 NO 2 S, the sulfoxide O atom is disordered over two sites with occupancies of 0.886 (4) and 0.114 (4), reflecting a partial inversion of the lone pair at the tetrahedral S-atom site. In the crystal, a supramolecular arrangement arises from weak intermolecular C-HÁ Á ÁO hydrogen bonds.contacts between the aromatic rings of symmetry-related molecules [centroid-centroid distances = 3.7547 (15) and 3.9577 (15) Å ] in parallel accumulation further stabilize the crystal structure.

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 find some new applications for phenothiazine derivatives in medicine, such as antitubercular (Wang et al., 2008) and antitumor (Lam et al., 2001). As a part of our program devoted to the new applications of phenothiazine derivatives in medicine, we report herein the crystal structure of the title compound, The molecular structure is shown in fig. 1, with the labeling scheme. The sulfoxide O atom is disordered over two sites (O1A and O1B) with occupancies of 0.88 and 0.12, respectively, corresponding to an inversion of the lone pair at tetrahedral S1 site.
The crystal structure of (I) consists of the self-assembly of the molecules through weak hydrogen bonding interactions of the kind C-H···O. The crystal packing (Fig. 2) consists of a wavy-like arrangement in the ab plane generated by intermolecular interactions of hydrogen bond between the O1A atom of sulfoxide and H atom H5 of the aromatic ring. On the other hand, π-π contacts between the aromatic rings [centroid to centroid distances = 3.7547 (15) and 3.9577 (15) Å ] in parallel accumulation may further stabilize the crystal structure.

Experimental
All reagents were of analytical grade. The title sample was prepared according to a literature method (Gilman & Nelson, 1953;Chan et al., 1998) from the N-benzylphenothiazine. The purity of the compound was checked by determining its melting point. It was characterized by recording its infrared spectra and elemental analyses. Single crystals of the title compound were obtained by slow evaporation of an ethanol solution. The X-ray diffraction studies were made at room temperature.

Refinement
H atoms bonded to C atoms were positioned geometrically (C-H = 0.93 and 0.96Å for benzene and methyl H atoms, respectively) and included in the refinement in the riding-model approximation, with U iso (H) = 1.2 or 1.5 U eq (C). The sulfoxide O atom is disordered over two positions with partial site-occupancies of 0.88 and 0.12, respectively, which were fixed in the last least-squares cycles.