Ethyl 6-methyl-8-phenyl-1,2,4-triazolo[1,5-a]pyridine-7-carboxylate

In title compound, C16H15N3O2, the 1,2,4-triazolo[1,5-a]pyridine ring system is almost planar (r.m.s. deviation = 0.0068 Å) and forms a dihedral angle of 61.4 (3)° with the phenyl ring. In the structure, centrosymmetrically related molecules are linked into dimers by pairs of C—H⋯N hydrogen bonds.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: RZ5092).
In title compound ( Fig. 1) the the [1,2,4]triazolo[1,5-a]pyridine ring system is almost planar, as indicated by its r.m.s. deviation of 0.0068 Å and by the dihedral angle of 0.9 (3)° between the pyridine and triazole rings. The C10-C15 phenyl ring is tilted by 61.4 (3)° with respect to the mean plane through the fused-ring system. All bond lengths (Allen et al., 1987) and angles in the molecule are normal. In the crystal structure, centrosymmetrically related molecules form dimeric units by a pair of C-H···N intermolecular hydrogen bonds (Table 1).

Experimental
Phenyl(1H-1,2,4-triazol-5-yl)methanone (6 mmol), ethyl 4-bromo-3-methylbut-2-enoate (12 mmol), potassium carbonate (1.8 g, 13.2 mmol) and DMF (30 ml) were added to a 100 ml round-bottomed flask and stirred for 8 h. The mixture was then poured into water (200 ml) and extracted with dichloromethane (3 × 50 ml). The organic layers were combined and dried over anhydrous Na 2 SO 4 , then filtered, and the mixture concentrated by rotary evaporation. The crude products were depurated by using column chromatography in 72% isolated yield. Crystals suitable for X-ray diffraction analysis were obtained by slow evaporation of a solution of the title compound in a hexane/ethyl acetate mixture (3:1 v/v) at room temperature over a period of one week.

Refinement
All H atoms were found on a difference Fourier map, with C-H = 0.93-0.97 Å and included in the final cycles of refinement using a riding model, with U iso (H) = 1.2U eq (C) or 1.5U eq (C) for methyl H atoms.

Computing details
Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT (Bruker, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).  The molecular structure of the title compouns, with displacement ellipsoids drawn at the 30% probability level. 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.