4-[(4-Ethoxyphenyl)aminoacetyl]-1,2,3,4-tetrahydro- quinoxalin-2-one

All interatomic distances in the title compound, C20H21N3O4, are normal. The heteroatom ring of the quinoxalinone system exists in a conformation intermediate between half-chair and sofa. The (4-ethoxyphenyl)amino moiety is nearly planar. The aminooxoethyl part can also be considered planar. There is one weak intramolecular C-H...O hydrogen bond in the structure. The structure is assembled by intermolecular N-H...O hydrogen bonds, to form a two-dimensional framework. One further C-H...O short intermolecular interaction is present in the structure.