Ethyl 2-(2-oxo-3-phenyl-1,2-di­hydro­quinoxalin-1-yl)acetate

In the title compound, C18H16N2O3, the di­hydro­quinoxaline moiety is planar (r.m.s. deviation = 0.0115 A) and the majority of the ester substituent is nearly perpendicular to its mean plane. In the crystal, the mol­ecules form oblique stacks along the b-axis direction through slipped π–π stacking inter­actions between adjacent di­hydro­quinoxaline units. C—H⋯O hydrogen bonds between the ester substituents on adjacent stacks form thick layers with the stacks on their outside surfaces. These layers extend along the c-axis direction and are coupled through C—H⋯π(ring) inter­actions. The structure was refined as a two-component twin.