Ethyl 3-(3-oxo-3,4-dihydroquinoxalin-2-yl)propanoate

In the title compound, C13H14N2O3, the fused ring system is almost planar (r.m.s. deviation = 0.015 Å). The r.m.s. deviation for all the non-H atoms of the molecule is 0.065Å. In the crystal, N—H⋯O and C—H⋯O hydrogen bonds generate polymeric chains along the b axis containing alternating centrsymmetric R 2 2(8) and R 2 2(20) loops.

In the title compound, C 13 H 14 N 2 O 3 , the fused ring system is almost planar (r.m.s. deviation = 0.015 Å ). The r.m.s. deviation for all the non-H atoms of the molecule is 0.065Å . In the crystal, N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds generate polymeric chains along the b axis containing alternating centrsymmetric R 2 2 (8) and R 2 2 (20) loops.

Comment
Benzopyrazine constitute an important class of nitrogen containing heterocyclic compounds. Literature has shown that these compounds possess a vide variety of applications from pharmaceutical to agricultural fields. Several benzopyrazines have been reported as anti-bacterial (Sona et al., 1998), anti-convulsant (Cai et al., 1997), anti-cancer (Toshima et al., 2003), antidiabetic (Benbow et al., 2007), antidepressant (Sarges et al., 1990), antifungal (Tandon et al., 2006), anti-inflammatory (Smits et al., 2008), etc. The present work is based on the synthesis of pyrazines derivatives which may possess enhanced pharmaceutical activities.
The cyclic carboxamide functional group from the pyrazine rings forms dimers through N-H···O type hydrogen bonding interaction which further connects through weak C-H···O type hydrogen bonding interaction to form the polymeric chain along b axes ( Fig. 2 Table 1).

Experimental
To the suspension of 3-(3-oxo-3,4-dihydroquinoxalin-2-yl)propanoic acid (Taylor et al., 1965) (5 g, 0.023 mol) in absolute ethanol (100 ml) was added 3N H 2 SO 4 (10 ml) and reaction mixture was refluxed for four hours. Solution was then concentrated under reduced pressure and neutralized with sodium bicarbonate solution to dissolve any unreacted acid. The precipitates were filtered under reduced pressure and washed with excess of water. The resulting ester was then recrystallized in absolute ethanol to yield colourless needles of (I). The product melted at 173-175 C (lit mp 160-162 C). (95% yield).

Refinement
All the C-H H-atoms were positioned with idealized geometry with C-H = 0.93 Å , C-H = 0.96 Å and C-H = 0.97 Å and were refined using a riding model with U iso (H) = 1.2 U eq (C) for aromatic and methylene and U iso (H) = 1.5U eq (C) for methyl C atoms. The N-H H atom were located in difference map with C-H = 0.96 Å with U iso (H) = 1.2 U eq (N). The reflection (011) was omitted during refinement as it was obscured by the beam stop.