1,8-Dibenzoyl-2,7-dimethoxynaphthalene

The molecule of the title compound, C26H20O4, is located on a twofold rotation axis. The two benzoyl groups are situated in an anti orientation. The dihedral angle between the mean planes of the phenyl ring and the naphthalene ring system is 80.25 (6)°. The phenyl and carbonyl groups in each benzoyl group are almost coplanar. The molecular packing is stabilized by weak C—H⋯O hydrogen bonds and a π–π stacking interaction between the phenyl rings [centroid–centroid and interplanar distances of 3.6383 (10) and 3.294 Å, respectively].


Comment
The molecules with naphthalene frame, especially, peri-substituted naphthalenes, have received much attention as unique structured aromatic core compounds for variety of the functional materials. Therefore, structural analyses of peri-substituted naphthalenes have been actively performed (Cohen et al., 2004;Gore & Henrick, 1980). Recently, we have reported the structure of 1,8-bis(4-chlorobenzoyl)-2,7-dimethoxynaphthalene (Nakaema et al., 2007). In this paper, the crystallographical structural characteristics of a 1,8-diphenylated naphthalene derivative having two methoxy groups at the 2,7-positions are described as the most simple homolog of the previously reported compound. The title compound was successfully synthesized by regioselective electrophilic aromatic substitution reaction of 2,7-dimethoxynaphthalene with benzoic acid.
ORTEPIII (Burnett & Johnson, 1996) plot of title compound is displayed in Fig. 1. The molecule of (I) lies across a crystallographic 2-fold axis so that the asymmetric unit contains one-half of the molecules. Thus, the two benzoyl groups are situated in anti orientation. The benzoyl groups are twisted away from the naphthalene moiety, and the dihedral angle is 80.25 (6)°. The torsion angles between the carbonyl groups and the naphthalene ring are −76.73 (18) and those between the carbonyl groups and the phenyl groups are 179.75 (15) In the crystal structure, the molecular packing of (I) is mainly stabilized by van der Waals interaction. In addition, the packing of the molecule is stabilized by relatively weak C-H···O hydrogen bonding, namely, C12-H12···O1 i [symmetry code: (i) x, -y+1, z + 1/2], C14-H14B···O1 ii [symmetry code: (ii) -x+1/2, y − 1/2, -z+1/2], and a π-π stacking interaction.
In the packing, the molecules are arranged by C-H···O hydrogen bonding along the c axis of the unit cell, and by a π-π stacking interaction perpendicular the bc plane of the unit cell (Fig. 2).

Experimental
The title compound was prepared by electrophilic aromatic diaroylation reaction of 2,7-dimethoxynaphthalene with benzoic acid. White single crystals suitable for X-ray diffraction were obtained by recrystallization from ethanol.

Refinement
All H atoms were found in a difference map and were subsequently refined as riding atoms, with C-H = 0.95 (aromatic) and 0.98 Å (methyl), and with U iso (H) = 1.2U eq (C).