8,15-Dioxa-10,13-diazatetracyclo[14.4.0.02,7.09,14]icosa-1(16),2,4,6,9(14),10,12,17,19-nonaene

The asymmetric unit of the title compound, C16H10N2O2, contains one half-molecule, the complete molecule being generated by twofold rotation symmetry. The plane of the pyrazine ring forms a dihedral angle of 64.87 (6)° with that of the benzene ring, and the planes of the two benzene rings are inclined to one another by 54.20 (6)°. The O atom deviates from the plane of the benzene ring by 0.1549 (8) Å. There are no significant intermolecular interactions in the crystal.

The asymmetric unit of the title compound, C 16 H 10 N 2 O 2 , contains one half-molecule, the complete molecule being generated by twofold rotation symmetry. The plane of the pyrazine ring forms a dihedral angle of 64.87 (6) with that of the benzene ring, and the planes of the two benzene rings are inclined to one another by 54.20 (6) . The O atom deviates from the plane of the benzene ring by 0.1549 (8) Å . There are no significant intermolecular interactions in the crystal.

Experimental
properties (Kawai et al., 2001;Abdullah, 2005). Pyrazine derivatives were shown to display antimycobacterial ( In the crystal, there are no significant intermolecular interactions present.
The reaction mixture was stirred at reflux for 12 h. The reaction mixture was allowed to cool to room temperature and then poured into water (200 mL), and extracted with CH 2 Cl 2 (2X100 mL). The combined organic layers were washed with water (100 mL), brine (50 mL) and dried over Na 2 SO 4 . The solvent was evaporated and the crude product was purified by column chromatography with CHCl 3 as an eluent to give the title compound. Single crystals suitable for X-ray diffraction were obtained by slow evaporation of a solution of the title compound in hexane at room temperature.

Refinement
The hydrogen atoms were placed in calculated positions and refined in the riding model approximation: C-H = 0.93 Å with U iso (H) = 1.2U eq (C).

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 > 2sigma(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq C1 0.53624 (10