6-Chloro-7-methyl-4-oxo-4H-chromene-3-carbaldehyde

In the title compound, C11H7ClO3, a chlorinated and methylated 3-formylchromone derivative, the non-H atoms are essentially coplanar (r.m.s. deviation = 0.0670 Å), with the largest deviation from the least-squares plane [0.2349 (17) Å] being for the pyran carbonyl O atom. In the crystal, molecules are linked through π–π stacking interactions along the a axis [centroid–centroid distance between the pyran rings = 3.824 (6) Å] and two stacks are connected by type I halogen–halogen interactions between the Cl atoms [Cl⋯Cl = 3.397 (3) Å].

In the title compound, C 11 H 7 ClO 3 , a chlorinated and methylated 3-formylchromone derivative, the non-H atoms are essentially coplanar (r.m.s. deviation = 0.0670 Å ), with the largest deviation from the least-squares plane [0.2349 (17) Å ] being for the pyran carbonyl O atom. In the crystal, molecules are linked throughstacking interactions along the a axis [centroid-centroid distance between the pyran rings = 3.824 (6) Å ] and two stacks are connected by type I halogen-halogen interactions between the Cl atoms [ClÁ Á ÁCl = 3.397 (3) Å ].
The University of Shizuoka is acknowledged for instrumental support.
The mean deviation of the least-square plane for the non-hydrogen atoms is 0.0670 Å, and the largest deviation is 0.2349 (17) Å for O3 ( Fig. 1).
In the crystal, the molecules are stacked with the translation-symmetry equivalent i [centroid-centroid distance between the pyran rings = 3.824 (6) Å, i: x + 1, y, z], as shown in Fig. 2. In addition, a type I halogen···halogen interaction is observed between the chlorine atoms at 6-position [Cl1···Cl1 ii = 3.397 (3) Å, C5-Cl1-Cl1 ii = 148.41 (7)°, ii: -x, -y, -z], as shown in Fig. 3 (bottom). Thus, a contact between the formyl oxygen atom and the chlorine atom at 6-position is not observed in the title compound. The chemical nature of the chlorine atom at 6-position in the title compound should be similar to that of the chlorine one at 6-position in 6,8-dichloro-4-oxochromene-3-carbaldehyde.

Synthesis and crystallization
Single crystals suitable for X-ray diffraction were obtained by slow evaporation of an acetonitrile solution of the commercially available title compound at room temperature.

Refinement
The C(sp 2 )-bound hydrogen atoms were placed in geometrical positions [C-H 0.95 Å, U iso (H) = 1.2U eq (C)], and refined using a riding model. One reflection (0 0 20) was omitted because of systematic error.  The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level.
Hydrogen atoms are shown as small spheres of arbitrary radius.

Figure 2
A packing view of the title compound.  Sphere models of the crystal structures of 6,8-dichloro-4-oxochromene-3-carbaldehyde (top), 6-chloro-4-oxo-4Hchromene-3-carbaldehyde (middle), and the title compound (bottom). Special details Refinement. Refinement was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F 2 . R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 σ(F 2 ) is used only for calculating R-factor (gt).