4-Hydroxy-6-methyl-3-[3-(thiophen-2-yl)acryloyl]-2H-pyran-2-one

The title compound, C13H10O4S, crystallizes with two molecules in the asymmetric unit in which the rings make dihedral angles of 3.9 (1) and 6.0 (1)°; this planarity is due in part to the presence of an intramolecular O—H⋯O hydrogen bond, which generates an S(6) ring in each molecule. Both molecules represent E isomers with respect to the central C=C bond. In the crystal, molecules are linked by C—H⋯O interactions into a three-dimensional network.

The title compound, C 13 H 10 O 4 S, crystallizes with two molecules in the asymmetric unit in which the rings make dihedral angles of 3.9 (1) and 6.0 (1) ; this planarity is due in part to the presence of an intramolecular O-HÁ Á ÁO hydrogen bond, which generates an S(6) ring in each molecule. Both molecules represent E isomers with respect to the central C C bond. In the crystal, molecules are linked by C-HÁ Á ÁO interactions into a three-dimensional network.
Chalcones also serve as precursors in the syntheses of different classes of flavonoids (Drexler, et al., 2003). Chalcone derivatives are also a class of organic compounds with excellent NLO properties (Fichou, et al., 1988), much better than those observed in inorganic crystals. Furthermore, several α,β-unsaturated ketones have been found to exhibit biological activity. In this paper, we report a structure containing both thiazole and α,β-unsaturated ketone moieties in one molecule.
The crystals do not exhibit second-order nonlinear optical properties as they crystallize in a centrosymmetric space group.
The title compound ( Fig. 1) exists in an E configuration with respect to the C7-C8 and C20-C21 double bonds. 6membered rings adopt a planar conformation. In the cyclic moiety with O2 atom, the r.m.s. deviation for the non-H atoms is 0.0154 Å, with the maximum deviation of C4 from the mean plane being 0.0222 (14) Å. In the moiety with O5 atom, the r.m.s. deviation for the non-H atoms is 0.0063 Å, with the maximum deviation of C17 from the mean plane -0.0105 (13) Å. The thiazole rings are also planar with a r.m.s deviation for non-H atoms of 0.0076 Å (ring with S1) & 0.0020 Å (ring with S2) with a maximum deviation of C9 from the mean plane being (-0.0107 (13)) Å and a maximum deviation of C24 from the mean plane of 0.0029 (15) Å respectively. With respect to the C7-C8 and C20-C21 bonds, the atom pairs C6/C9, H7/H8 and C19/C20, H20/H21 are all trans, shown by the value of (-0.05 (14)°) for O8-C21-C20-C19 and 0.42 (15)°) for C6-C7-C8-O4 -0.42 (15)° torsion angle. The double-bond character of the bond between C7 and C8 is deduced from the short bond distance [1.339 (3) Å]. The value in the other molecule is 1.339 (3) Å for C20/C21].
All bond lengths and angles in (I) have normal values (Allen, et al. 1987).

Experimental
Dehydroacetic acid (0.168 g, 1 mmol) in 1 ml of piperidine was added to thiofene-2-carboxaldehyde (0.112 g, 1 mmol) of in 25 ml of chloroform and then refluxed with stirring under nitrogen atmosphere for 3 days. After that, 5-7 ml of the chloroform-water azeotrope mixture were removed by simple distillation. The product were obtained by slow evaporation of the remaining chloroform and washed with ethyl acetate (2x5ml), then it was recrystalized from dichlromethane and The methyl H atoms were constrained to an ideal geometry (C-H = 0.96 Å) with U iso (H) = 1.2Ueq(C), but were allowed to rotate freely about the C-C bonds.

Figure 1
The structure of the title compound in 50% probability ellipsoids.