6-Chloro-2-phenyl-3-(2-phenylethynyl)quinoxaline

In the title compound, C22H13ClN2, the quinoxaline ring system is close to planar [maximum deviation = 0.061 (2) Å]. The phenyl ring at the 2-position and the phenyl ring of the phenylethynyl substituent make dihedral angles of 49.32 (7) and 11.99 (7) °, respectively, with the quinoxaline mean plane. The two phenyl rings are inclined to one another by 61.27 (9)°. In the crystal, molecules are linked by C—H⋯π and π–π interactions [centroid–centroid distances = 3.6210 (12) and 3.8091 (12) Å].


Experimental
Cg2 is the centroid of the C17-C22 ring.

Comment
The design of small molecular weight compounds has aroused much interest in the past decades due to the advances in targeted therapeutics coupled with novel techniques in target identification. It is well know that quinoxalines have broad applications in the fields of medicine and pharmaceuticals. It has been shown that many quinoxaline derivatives exhibit good biological activities, such as antituberculous activities (Rodrigo et al., 2002), antioxidative properties (Watkins et al., 2009), andantidyslipidemic (Sashidhara et al., 2009). Recently, a large number of crystal structures of quinoxaline derivatives have been reported (Hegedus et al., 2003;Naraso et al., 2006;Hassan et al., 2010;Ammermann et al., 2008;Daouda et al., 2011;Ramli et al., 2012).
In the title compound ( Fig. 1) the phenyl ring of the phenylethynyl substituent is twisted by 11.99 (7)° out of the mean plane of the quinoxaline fused-ring system [planar to within 0.061 (2) Å]. The phenyl ring of the substituent at the 2position, C7, makes dihedral angles of 49.32 (7)° and 61.27 (9)°, respectively, with the quinoxaline mean plane and the phenylethynyl phenyl ring.
Footnote to Table 1: Cg2 is the centroid of the C17-C22 ring.
Experimental 4-Chloro-1,2-diaminobenzene (2.5 mmol), CuCl (0.1 mmol), chlorobenzene (3 ml) and phenylethynylene(1 mmol) were added to a sealed tube and heated to 343 K by stirring. After the completion of the reaction (as monitored by TLC), the inorganic material salt was filtered and the reaction mixture was extracted with EtOAc. The mixture was separated after washed by saturated NaCl solution, then the oily layer was dried by anhydrous sodium sulfate and the solvent was removed under reduced pressure. The crude product obtained was purified by column chromatography (eluent: 50:1 Petroleum ether-EtOAc) to give the title compound. Block-like yellow crystals were obtained by slow evaporation of the solvents.

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.