3-[(4-Oxo-4H-thiochromen-3-yl)methyl]-4H-thiochromen-4-one

The title molecule, C19H12S2O2, lies on a twofold rotation axis. The thiochromonone unit is essentially planar, with a maximum deviation of 0.0491 (14) Å. The dihedral angle between the thiochromenone ring systems is 64.48 (4)°. In the crystal, there are weak π–π stacking interactions, with a centroid–centroid distance of 3.7147 (9) Å.

The molecular structure of (I) is shown in Fig. 1. The molecule lies on a twofold rotation axis. The unique thiochromonone unit is essentially planar with a maximum deviation of 0.0491 (14) Å for atom C6. The planarity of this unit can be attributed to the sp 2 hybridized nature of the aromatic benzene unit and the fused olefinic thiopyranone unit. This is similar to the case of a methylene bridged chromenone example found in the literature (Ambartsumyan et al., 2012).

Experimental
To a stirred solution of 4-chloro-2H-thiochromene-3-carbaldehyde (0.5 g, 0.0025 mol) in freshly dried DMSO (6.0 mL) was added dried potassium fluoride (0.3 g, 0.005 mol) and then heated to 343-353K. After completion of the reaction by TLC, the reaction mass was cooled to 303-308K and then quenched with 50 ml of water. The mixture was extracted with ethyl acetate (2 x 30 ml). The combined organic portion was washed with water (2 x 25 mL), dried over anhydrous sodium sulphate and then concentrated under reduced pressure to yield a brown paste. Purification of the crude product by column chromatography yielded the title bis methylene chromanone. 50 mg of the title compound was dissolved in 2 ml of methanol, and warmed to 323K for complete dissolution, then filtered, and the clear solution was stored at room temperature. After 2 days, pale yellow crystals were formed.

Refinement
H atoms bonded to sp 2 C atoms were placed in calculated positions with C-H = 0.93Å and U iso (H) = 1.2U eq (C). The unique H atom conded to C10 was refined independently with an isotropic displacement factor.

Figure 2
Part of the crystal structure illustrating the π..π stacking interactions.

3-[(4-Oxo-4H-thiochromen-3-yl)methyl]-4H-thiochromen-4-one
Crystal data C 19 H 12 O 2 S 2 M r = 336.41 Monoclinic, C2/c Hall symbol: -C 2yc a = 11.9480 (5) Å b = 11.8649 (5) Å c = 11.1416 (5) Å β = 108.918 (2)°V = 1494.14 (11) Å 3 Z = 4 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.