2-(Naphthalen-1-yl)-4-(thiophen-2-ylmethylidene)-1,3-oxazol-5(4H)-one

The asymmetric unit of the title compound, C18H11NO2S, contains two crystallographically independent molecules. In one molecule, the oxazole and thiophene rings are oriented at dihedral angles of 17.40 (9) and 18.18 (7)° with respect to the naphthalene ring system, while the oxazole and thiophene rings are oriented to each other at a dihedral angle of 0.86 (9)°. In the other molecule, the corresponding angles are 3.05 (8), 9.62 (6) and 7.02 (8)°, respectively. In each molecule, a weak intramolecular C—H⋯N hydrogen bond links the oxazole N atom to the naphthalene group. Weak intermolecular C—H⋯O hydrogen bonding is present in the crystal structure. π–π stacking between the oxazole and thiophene rings, between the thiophene and naphthalene rings, and between the oxaozole and naphthalene rings, [centroid–centroid distances = 3.811 (2), 3.889 (2), 3.697 (2) and 3.525 (2) Å] may further stabilize the crystal structure.

The asymmetric unit of the title compound, C 18 H 11 NO 2 S, contains two crystallographically independent molecules. In one molecule, the oxazole and thiophene rings are oriented at dihedral angles of 17.40 (9) and 18.18 (7) with respect to the naphthalene ring system, while the oxazole and thiophene rings are oriented to each other at a dihedral angle of 0.86 (9) . In the other molecule, the corresponding angles are 3.05 (8), 9.62 (6) and 7.02 (8) , respectively. In each molecule, a weak intramolecular C-HÁ Á ÁN hydrogen bond links the oxazole N atom to the naphthalene group. Weak intermolecular C-HÁ Á ÁO hydrogen bonding is present in the crystal structure.stacking between the oxazole and thiophene rings, between the thiophene and naphthalene rings, and between the oxaozole and naphthalene rings, [centroid-centroid distances = 3.811 (2), 3.889 (2), 3.697 (2) and 3.525 (2) Å ] may further stabilize the crystal structure.

Comment
The design and syntheses of new conjugated polymers are a significant part of the conducting polymers research and have attracted great attention. Various aromatic ring-based conjugated polymers have been developed for use in potential applications, such as organic light-emitting diodes (OLEDs) (Liu et al., 2007;Allard et al., 2008), organic thin-film transistors (OTFTs) (Woudenbergh et al., 2004;Zhang et al., 2007), and organic photovoltaics (OPVs) (Güneş et al., 2007;Soci et al., 2007). Among conducting polymers, polythiophene and its derivatives have become a subject of considerable interest as electrochromic materials, due to their chemical stabilities. Thiophene based molecules are widely used in the sytheses of the charge transporting molecules used in organic field effect transistors, organic solar cells and organic light emitting diodes (Mas-Torrent & Rovira, 2008;Shirota & Kageyama, 2007;Varis et al., 2006). The present study was undertaken to ascertain the crystal structure of the title compound.
The asymmetric unit of the title compound contains two crystallographically independent molecules. Each molecule consists of an oxazol ring, a thiophene ring and a naphthalene group (Fig. 1), where the bond lengths are close to standard values (Allen et al., 1987). In each molecule, the intramolecular C-H···N hydrogen bonds link the oxazol nitrogen atoms to the naphthalene groups (Table 1 and Fig. 1).
An examination of the deviations from the least-squares planes through individual rings shows that rings A ( In the crystal, intermolecular C'-H'···O' hydrogen bonds link the molecules into centrosymmetric dimers, in which they are also linked through C'-H'···O and C-H···O hydrogen bonds to form a three dimensional network (Table 1 and Fig. 2).

Experimental
For the preparation of the title compound, (I), thiophene-2-carbaldehyde (0.46 g, 5 mmol), naphthalen-1-yl glycine (1.14 g, 5 mmol), acetic anhydride (2.49 ml, 12 mmol) and sodium acetate (0.41 g, 5 mmol) were heated until the mixture just supplementary materials sup-2 liquefied, and then heating was continued for a further 2 h at 353 K. After completion of the reaction, ethanol (25 ml) was added and the mixture was kept at room temperature for 18 h. The solid product obtained was purified by washing with cold ethanol, hot water and a small amount of hexane, respectively. It was crystallized from hot ethanol (yield; 0.23 g, 49%, m.p. 460 K).

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
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 > 2sigma(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.