Methyl 2-oxo-2H-chromene-3-carboxylate

The title compound, C11H8O4, features an almost planar molecule (r.m.s. deviation = 0.033 Å for all non-H atoms). In the crystal, the molecules are linked via C—H⋯O hydrogen bonds, forming two-dimensional networks lying parallel to (1-21).

The title compound, C 11 H 8 O 4 , features an almost planar molecule (r.m.s. deviation = 0.033 Å for all non-H atoms). In the crystal, the molecules are linked via C-HÁ Á ÁO hydrogen bonds, forming two-dimensional networks lying parallel to (121).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SU2501).
The title compound, Fig. 1, features an almost planar molecule (r.m.s. deviation = 0.033 Å for all non-H atoms). The maximum deviation from the mean plane being 0.0734 (12) Å for atom O2.
In the crystal, molecules are linked via C-H···O hydrogen bonds forming two-dimensional networks lying parallel to (121); Table 1

Experimental
Salicylaldehyde (1.22 g, 0.01 mol) and diethylmalonate (1.6 g, 0.01 mol) were dissolved in ethanol to give a clear solution. Piperidine (2 ml) was added and the mixture was refluxed for 5 h. The content was concentrated to a small volume. The product (3) was poured onto crushed ice, filtered out and crystallized from ethanol to give colourless crystals, m.p. 393-395 K; Yield: 90%. Spectroscopic data for the title compound are available in the archived CIF.

Refinement
All the H atoms were included in calculated positions and treated as riding atoms: C aromatic -H = 0.95 Å and C methyl -H = 0.98 Å, with U iso (H) = 1.2U eq (C) or U iso (H) = 1.5U eq (C methyl ). SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL-Plus (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008   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 R-factors(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.