{2,7-Dimethoxy-8-[4-(2-methylpropyl)benzoyl]naphthalen-1-yl}[4-(2-methylpropyl)phenyl]methanone

In the molecule of the title compound, C34H36O4, the two 4-isobutylbenzoyl groups at the 1- and 8-positions of the naphthalene ring system are aligned almost antiparallel, and the benzene rings make a dihedral angle of 21.59 (7)°. The dihedral angles between the benzene rings and the naphthalene ring system are 69.26 (6) and 64.29 (5)°. There are no classical hydrogen bonds in the structure, but inversion-related molecules engage in π–π stacking, with an interplanar spacing between related naphthalene groups of 3.4120 (16) Å.

In the molecule of the title compound, C 34 H 36 O 4 , the two 4isobutylbenzoyl groups at the 1-and 8-positions of the naphthalene ring system are aligned almost antiparallel, and the benzene rings make a dihedral angle of 21.59 (7) . The dihedral angles between the benzene rings and the naphthalene ring system are 69.26 (6) and 64.29 (5) . There are no classical hydrogen bonds in the structure, but inversionrelated molecules engage instacking, with an interplanar spacing between related naphthalene groups of 3.4120 (16) Å .   et al., 2012). The aroyl groups in these compounds are almost perpendicular to the naphthalene rings, and are oriented in opposite directions (anti-orientation). Moreover, we have also clarified that the aroyl groups of 2,7-dimethoxy-1,8-bis(4-phenoxybenzoyl)naphthalene (Hijikata et al., 2010) are oriented in the same direction (syn-orientation). As part of our ongoing studies on the molecular structures of these kinds of homologous molecules, the X-ray crystal structure of the title compound, 1,8-diaroylatednaphthalene bearing isobutyl groups, is discussed in this article.

Related literature
The molecular structure of the title compound is displayed in Fig 1. Two 4-isobutylbenzoyl groups are situated in the anti-orientation. The dihedral angle between the best planes of the two phenyl rings is 21.59 (7)°. The dihedral angles between the best planes of the 4-isobutylphenyl rings and the naphthalene ring are 69.26 (6)° and 64.29 (5)°.
The C═O bond of the ketonic carbonyl moiety (C12═O4), carbon atom (C31) of isobutyl groups, and benzene ring lie In the molecular packing, C-H···O interactions between the carbonyl oxygen atoms and hydrogen atoms of benzene ring are observed along b axis. The C-H···O interactions effectively contribute to stabilization of the molecular alignment (C21-H21···O4 = 2.34 Å; symmetry code: x,-1 + y, z; Fig. 2).

Experimental
To a 50 ml flask, 4-isobutylbenzoic acid (1.96 g, 11.0 mmol), phosphorus pentoxide-methanesulfonic acid mixture dried over anhydrous MgSO 4 . The solvent was removed under reduced pressure to give cake (100% yield). The crude product was purified by recrystallization from methanol (32% yield). Colorless platelet single crystals suitable for X-ray diffraction were obtained by repeated crystallization from ethanol.

Computing details
Data    where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.17 e Å −3 Δρ min = −0.15 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0022 (2) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > 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.