8-Chloro-4-oxo-4H-chromene-3-carbaldehyde

In the title compound, C10H5ClO3, a chlorinated 3-formylchromone derivative, all atoms are essentially coplanar (r.m.s. deviation = 0.032 Å for the non-H atoms), with the largest deviation from the least-squares plane [0.0598 (14) Å] being for a pyran-ring C atom. In the crystal, molecules are linked through stacking interactions along the b axis [shortest centroid–centroid distance between the pyran and benzene rings = 3.566 (2) Å].

In the title compound, C 10 H 5 ClO 3 , a chlorinated 3-formylchromone derivative, all atoms are essentially coplanar (r.m.s. deviation = 0.032 Å for the non-H atoms), with the largest deviation from the least-squares plane [0.0598 (14) Å ] being for a pyran-ring C atom. In the crystal, molecules are linked through stacking interactions along the b axis [shortest centroid-centroid distance between the pyran and benzene rings = 3.566 (2) Å ].
The University of Shizuoka is acknowledged for instrumental support.
Supporting information for this paper is available from the IUCr electronic archives (Reference: ZL2591).

Comment
Halogen bonds have been found to occur in organic, inorganic, and biological systems, and have recently attracted much attention in medicinal chemistry, chemical biology and supramolecular chemistry (Auffinger et al., 2004, Metrangolo et al., 2005, Wilcken et al., 2013, Sirimulla et al., 2013. We have recently reported the crystal structures of chlorinated 3formylchromone derivatives 6,8-dichloro-4-oxochromene-3-carbaldehyde (Ishikawa & Motohashi, 2013, Fig.2 (top)) and 6-chloro-4-oxo-4H-chromene-3-carbaldehyde (Ishikawa, 2014, Fig.2 (middle)). It was found that a halogen bond is formed for 6,8-dichloro-4-oxochromene-3-carbaldehyde between the formyl oxygen atom and the chlorine atom at the 8position, but none is formed for 6-chloro-4-oxo-4H-chromene-3-carbaldehyde between the formyl oxygen atom and the chlorine atom at the 6-position. As part of our interest in this type of chemical bonding, we herein report the crystal structure of a monochlorinated 3-formylchromone derivative 8-chloro-4-oxo-4H-chromene-3-carbaldehyde. The objective of this study is to reveal whether halogen bond(s) can be formed in the crystal of the title compound with the chlorine atom at 8-position and without a halogen atom at 6-position.
The mean deviation of the least-square planes for the non-hydrogen atoms is 0.0316 Å, and the largest deviation is 0.0598 (14) Å for C1. These mean that these atoms are essentially coplanar. In the crystal, the molecules are stacked with their inversion-symmetry equivalent along the b-axis direction [centroid-centroid distance between the pyran and benzene rings of the 4H-chromene units = 3.566 (2) Å, symmetry operator i: -x + 1, -y + 1, -z + 2], as shown in Fig.1.

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.