10-(Prop-2-yn-1-yl)-2,7-diazaphenothiazine1

In the title molecule [systematic name: 10-(prop-2-yn-1-yl)dipyrido[3,4-b:3′,4′-e][1,4]thiazine], C13H9N3S, the dihedral angle between the two pyridine rings is 146.33 (7)° and the angle between two halves of the thiazine ring is 138.84 (8)°, resulting in a butterfly shape for the tricyclic system. The central thiazine ring adopts a boat conformation, with the 2-propynyl substituent at the thiazine N atom located in a pseudo-equatorial position and oriented to the concave side of the diazaphenothiazine system. In the crystal, molecules are arranged via π–π interactions between the pyridine rings [centroid–centroid distances = 3.838 (1) and 3.845 (1) Å] into stacks extending along [001]. There are C—H⋯C and C—H⋯N interactions between molecules of neighbouring stacks.

In the title molecule [systematic name: 10-(prop-2-yn-1-yl)dipyrido[3,4-b:3 0 ,4 0 -e] [1,4]thiazine], C 13 H 9 N 3 S, the dihedral angle between the two pyridine rings is 146.33 (7) and the angle between two halves of the thiazine ring is 138.84 (8) , resulting in a butterfly shape for the tricyclic system. The central thiazine ring adopts a boat conformation, with the 2propynyl substituent at the thiazine N atom located in a pseudo-equatorial position and oriented to the concave side of the diazaphenothiazine system. In the crystal, molecules are arranged viainteractions between the pyridine rings [centroid-centroid distances = 3.838 (1) and 3.845 (1) Å ] into stacks extending along [001]. There are C-HÁ Á ÁC and C-HÁ Á ÁN interactions between molecules of neighbouring stacks.
Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Burnett & Johnson, 1996) and Mercury (Macrae et al., 2008); software used to prepare material for publication: publCIF (Westrip, 2010). Phenothiazines exhibit not only recognized neuroleptic, antihistaminic and antitussive activities but recently also anticancer, antibacterial and reversal multidrug resistance [Aaron et al., (2009);Pluta et al., (2011)]. The modifications of the phenothiazine structures are mainly directed into the introduction of new pharmacophoric substituents at the thiazine nitrogen atom and the substitution of the benzene ring with an azine ring (Pluta et al., , 2011. Synthesis of substituted 10-(2-propynyl)phenothiazines and their transformations into various aminobutynyl derivatives of anticancer and multidrug resistance reverting activities was reported by Bisi et al. (2008). We modified the phenothiazine structure via the substitution of the benzene ring with the pyridine ring to form 2,7-diazaphenothiazines ) possessing anticancer and immunosuppressive activities (Zimecki et al., 2009;Pluta et al. 2010). Alkylation of azaphenothiazines proceeds at the thiazine and/or the azine nitrogen atoms, depending on the reaction conditions . N-Alkylation of 10H-2,7-diazaphenothiazine led to both types of the products showing planar and folded 2,7-diazaphenothiazine ring system . 10H-2,7-Diazaphenothiazine was transformed into the title compound, C 13 H 9 N 3 S, a convenient substrate to other 2,7-diazaphenothiazine derivatives using aminomethylation or 1,3-dipolar cycloaddition. The X-ray study showed the propynyl group to be attached to the thiazine nitrogen atom. In the molecule, the butterfly angle between the two pyridine rings is 146.33 (7)° and the angle between two halves of the thiazine ring is 138.84 (8)°. The 2-propynyl substituent is in a pseudo-equatorial position with the angle S5···N10-C11 of 163.8 (2)° and directed to the concave side of the diazaphenothiazine system with the angle between the N10/C11/C12/C13 and C4a/C5a/C9a/C10a planes of 86.3 (1)°. The thiazine nitrogen atom shows pyramidality as the sum of the C-N10-C bond angles is 356.1 (1)°. Hydrogen bond C4-H4···N2 (Table 1) results in one-dimensional polymeric chain parallel to the b axis. Acidic hydrogen atom H13 is in close contact to C11 and C12 atoms of the propynyl substituent (both H···C distances equal to 2.78 Å). This suggests, that H13 is involved in C-H···C interactions to these two carbon atoms rather than in the C-H···π interaction to the π system of the triple C12≡C13 bond (H13···center C12≡C13 distance of 2.96 Å ). Additionally, the C12≡ C13 bond π electrons interact with two aromatic H atoms (H3 and H8) of two other adjacent molecules with short C-H···C intermolecular contacts (less than the sum of van der Waals radii) between H3 and H8, and C13 (see Table 1). On the basis of these interactions a three-dimensional network is formed.

Experimental
To a suspension of 10H-2,7-diazaphenothiazine (100 mg, 0.5 mmol) in 5 ml DMF potassium tert-butoxide (80 mg, 0.72 mmol) was added. The mixture was stirred at room temperature for 1 h. Then a solution of propargyl bromide (80 mg, 0.64 mmol) in toluene was added dropwise. The solution was stirred at room temperature for 24 h and poured into water

Refinement
All H atoms in the were treated as riding atoms in geometrically idealized positions, with C-H distances of 0.95 (aromatic and acetylene) or 0.99 Å (methylene), and with U iso (H) = 1.2U 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 > 2σ(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.