3-Methyl-1H-pyrrolo[2,1-c][1,4]oxazin-1-one

In the title molecule, C8H7NO2, all the non-H atoms lie essentially in the same plane (r.m.s. deviation = 0.019 Å) In the crystal structure, weak intermolecular C—H⋯O interactions link molecules into chains along [100]. In addition, there are π–π stacking interactions between molecules related by the c-glide plane, with alternating centroid–centroid distances of 3.434 (2) and 3.639 (2) Å.

After 24 h, the solid was removed by filtration and washed with acetone. The filtrate was concentrated under reduced pressure by rotary evaporator, the residue was partitioned between water and ethyl acetate (200 ml each) in a separatory funnel (500 ml). The organic layer was separated and the aqueous phase was washed with ethyl acetate (100 ml x 2). The combined organic layers were washed successively with water (100 ml x 3) and brine solution and dried over anhydrous MgSO 4 . After filtration, the solvent was removed by rotary evaporator to obtain the oily brown solid residue (13.0 g) which was purified by flash column chromatography (Petroleum ether: Ethyl acetate; 2:1) to afford the desired compound as pale yellow solid (5.1 g, 57%). The product was recrystallized in a mixture of petroleum ether and ethyl acetate (5:1). The colorless needles of the title compound were obtained by slow evaporation of solvent at room temperature. Melting point and NMR spectral data were consistent with the reported values (Dumas, 1988).

Refinement
H atoms were placed in calculated positions with C-H = 0.95Å or C-H = 0.98Å for methyl H atoms and were included in the refinement in a riding-model approximation with U iso (H) = 1.2U eq (C) or 1.5U eq (C methyl ).
supplementary materials sup-2 Figures   Fig. 1. The molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
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 > σ(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.