3-Bromochroman-4-one

The heterocyclic ring of the title compound, C9H7BrO2, obtained by bromination of 4-chromanone with copper bromide, adopts a half-chair conformation. The supramolecular structure is governed by a weak C—H⋯O hydrogen bond. There is also π–π stacking between symmetry-related benzene rings; the centroid–centroid distance is 3.9464 (18), the perpendicular distance between the rings is 3.4703 (11) and the offset is 1.879 Å.

The heterocyclic ring of the title compound, C 9 H 7 BrO 2 , obtained by bromination of 4-chromanone with copper bromide, adopts a half-chair conformation. The supramolecular structure is governed by a weak C-HÁ Á ÁO hydrogen bond. There is alsostacking between symmetry-related benzene rings; the centroid-centroid distance is 3.9464 (18), the perpendicular distance between the rings is 3.4703 (11) and the offset is 1.879 Å .
In the title compound, the pyranone moiety is fused with the benzene ring and adopts a half chair conformation. The dihedral angle between the benzene ring and the (C 3 -C 2 -O 1 ) of the pyranone moiety is 43.03 (17)° and C2 flips out of the plane of the benzene ring by 0.5734 (31) Å (Fig. 1).

Experimental
To a mixture of copper bromide (II) (11.351 g, 50.673 mmol) in ethyl acetate, chloroform (20:20 ml) was stirred under inert atmosphere at room temperature. Into this mixture, chroman-4-one (5 g, 33.783 mmol) in chloroform (20 ml) was added and the reaction mixture refluxed vigorously under inert atmosphere at 70 °C for 6 h. Completion of the reaction was monitored by thin layer chromatography. Upon completion, the reaction mixture was cooled, filtered and washed with chloroform (20 ml). The filtrate solution was evaporated under reduced pressure to get the pure title compound with a yield of 86%.

Refinement
All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed in idealized positions and refined with geometrical constraints. The structure was refined to a R factor of 0.0251. program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figure 1
The molecular structure of the title compound, with atom labels and anisotropic displacement ellipsoids (drawn at 50% probability level). 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.