Crystal structure of 3-amino-2-ethylquinazolin-4(3H)-one

The molecule of the title compound, C10H11N3O, is planar, including the ethyl group, as indicated by the N—C—C—C torsion angle of 1.5 (2)°. In the crystal, inversion-related molecules are stacked along the a axis. Molecules are oriented head-to-tail and display π–π interactions with a centroid-to-centroid distance of 3.6664 (8) Å. N—H⋯O hydrogen bonds between molecules generate a ‘step’ structure through formation of an R 2 2(10) ring.

Supporting information for this paper is available from the IUCr electronic archives (Reference: HG5454).

S2.1. Synthesis and crystallization
A mixture of methyl 2-aminobenzoate and propionic anhydride (1.4 mole equivalents) was heated for 30 minutes at 105 °C. The mixture was cooled to 75 °C and diluted with ethanol (50 mL). Hydrazine monohydrate (10 mole equivalents) was added in a dropwise manner over 10 minutes and the mixture was refluxed for 1 h. The mixture was cooled to room temperature and the solvent was removed under reduced pressure. The residue obtained was purified by column chromatography (silica gel hexane/diethyl ether in 4:1 by volume) to give 3-amino-2-ethylquinazolin-4(3H)-one in 82% yield (Davies et al., 2010). Crystallization from a mixture of ethyl acetate and diethyl ether (1:2 by volume) gave colourless crystals of the title compound. The spectroscopic data for the title compound were identical with those reported (Davies et al., 2010).

S2.2. Refinement
H atoms were positioned geometrically and refined using a riding model with U iso (H) constrained to be 1.2 times U eq for the atom it is bonded to except for methyl groups where it was 1.5 times with free rotation about the C-C bond. The amide hydrogen atoms were located in the difference Fourier map and refined freely.

Figure 1
The asymmetric unit of C 10 H 11 N 3 O, with atom labels and 50% probability displacement ellipsoids for non-hydrogen atoms.

Figure 2
Crystal packing with hydrogen-bonding contacts shown as dotted lines.