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

In the title compound, C24H15NO2, the oxazole ring is oriented at dihedral angles of 10.09 (4) and 6.04 (4)° with respect to the mean planes of the naphthalene ring systems, while the two naphthalene ring systems make a dihedral angle of 4.32 (3)°. Intramolecular C—H⋯N hydrogen bonds link the oxazole N atom to the naphthalene ring systems. In the crystal, intermolecular weak C—H⋯O hydrogen bonds link the molecules into centrosymmetric dimers. π–π contacts between the oxazole and naphthalene rings and between the naphthalene ring systems [centroid–centroid distances = 3.5947 (9) and 3.7981 (9) Å] may further stabilize the crystal structure. Three weak C—H⋯π interactions also occur.

In the title compound, C 24 H 15 NO 2 , the oxazole ring is oriented at dihedral angles of 10.09 (4) and 6.04 (4) with respect to the mean planes of the naphthalene ring systems, while the two naphthalene ring systems make a dihedral angle of 4.32 (3) . Intramolecular C-HÁ Á ÁN hydrogen bonds link the oxazole N atom to the naphthalene ring systems. In the crystal, intermolecular weak C-HÁ Á ÁO hydrogen bonds link the molecules into centrosymmetric dimers.contacts between the oxazole and naphthalene rings and between the naphthalene ring systems [centroid-centroid distances = 3.5947 (9) and 3.7981 (9) Å ] may further stabilize the crystal structure. Three weak C-HÁ Á Á interactions also occur.

Comment
Oxazolones that are internal anhydrides of acyl amino acids are important class of five-membered heterocycles. They are highly versatile intermediates used for the syntheses of several organic molecules, including amino acids, peptides (Gottwald & Seebach, 1999;Meiwes et al., 1997), antimicrobial or antitumor compounds (Martinez et al., 1964;Gelmi et al., 1997), immunomodulators, heterocyclic precursors for biosensors coupling (Croce et al., 1994;Cannella et al., 1996) and/or photosensitive composition devices for proteins (Kojima et al., 1998). They can be easily prepared from N-acyl amino acids by dehydration. 5-Oxazolones have also a wide range of applications including their use in semiconductor devices because of their promising photophysical and photochemical activities (Gündoğdu et al., 2010). The present study was undertaken to ascertain the crystal structure of the title compound.
The title compound consists of an oxazol ring and two naphthalene groups ( Fig. 1), where the bond lengths are close to standard values (Allen et al., 1987). 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
) and E (C19-C24) are planar. The naphthalene groups, containing the rings A, B and D, E are also nearly planar [with maximum deviations of 0.022 (2) Å for atom C6 and -0.061 (2) Å for atom C17] with dihedral angles of A/B = 1.62 (3) and D/E = 3.58 (4) °. Ring C is oriented with respect to the planar naphthalene groups at dihedral angles of 10.09 (4) and 6.04 (4) °, respectively, while the two naphthalene groups are oriented at a dihedral angle of 4.32 (3)°.

Experimental
For the preparation of the title compound, (I), α-naphtaldehyde (0.74 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 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; 0.22 g, 30%, m.p. 453 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.