Methyl pyrido[2,3-b]pyrazine-3-carboxylate

The asymmetric unit of the title compound, C9H7N3O2, is composed of two independent molecules. The crystal structure is stabilized by C—H⋯O and C—H⋯N hydrogen bonds, forming a three-dimensional network. The crystal structure also features pyrazine–pyrazine π–π interactions [centroid–centroid distance = 3.6994 (5) Å] and also pyridine–pyrazine π–π interactions [centroid–centroid distance = 3.6374 (5) Å].


Comment
Heterocyclic esters are important compounds in respect of their biological and pharmaceutical characteristics (Listvan et al., 2002;Li et al., 2007). Recently we have developed a mild methodology for the synthesis of heterocyclic esters from their corresponding aldehydes (Goswami & Hazra, 2009;Goswami et al., 2011). Here we report the crystal structure of methyl pyrido[2,3-b]pyrazine-3-carboxylate.
The asymmetric unit of the title compound consists of two crystallographically independent methyl pyrido[2,3b]pyrazine-3-carboxylate molecules, (A & B), as shown in Fig. 1. The bond lengths of molecules A and B agree with each other and are within normal ranges (Allen et al., 1987).

Refinement
All hydrogen atoms were positioned geometrically, with Csp 2 -H = 0.93 Å and C(methyl)-H = 0.96 Å; they were refined using a riding model, with U iso (H) = xU eq (C), where x = 1.5 for methyl H and 1.2 for all other H atoms. A rotating group model was applied to the methyl groups.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The 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 Rfactors(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.