1,3-Bis(2-methylprop-2-enoyl)-1H-benzimidazol-2(3H)-one

The molecules of the title compound, C15H14N2O3, possesses crystallographically imposed twofold rotational symmetry, so the asymmetric unit contains one half-molecule. The fused-ring system deviates significantly from planarity; the planes of the five- and six-membered rings are twisted with respect to each other by 3.0 (1)°. In the crystal, weak C—H⋯O hydrogen bonds link molecules related by translation in [010] into chains.

The molecules of the title compound, C 15 H 14 N 2 O 3 , possesses crystallographically imposed twofold rotational symmetry, so the asymmetric unit contains one half-molecule. The fusedring system deviates significantly from planarity; the planes of the five-and six-membered rings are twisted with respect to each other by 3.0 (1) . In the crystal, weak C-HÁ Á ÁO hydrogen bonds link molecules related by translation in [010] into chains.
In (I) (Fig. 1), all bond lengths and angles are normal and comparable with those reported for related compounds (Ouzidan et al., 2011;Kandri Rodi et al., 2011). The molecules in (I) possess a crystallographically imposed twofold rotational symmetry, with half of the molecule in the assymetric unit. The five-and six-membered rings are twisted with a dihedral angle of 3.0 (1)°.
In the crystal, weak intermolecular C-H···O hydrogen bonds (Table 1)

link the molecules related by translation in
[010] into chains.
Methacrylic anhydride (2.29 g, 0.014 moles) was added slowly, using a syringe, with stirring. The mixture was allowed to cool to 0 °C using ice-salt mixture with stirring. The mixture was treated with sodium hydroxide (0.56 g, 0.014 moles) drop by drop and the amide formation reaction was allowed to stir for 6 h at RT. The resulting crude product was dissolved in ethyl acetate, washed with bicarbonate solution and then with water thrice followed by brine solution and dried over anhydrous sodium sulfate. The resulting solvent was removed by rotary evaporation. The product was purified by column chromatography technique using 12% ethyl acetate in hexane as the eluent to obtain a product as a bright white solid. Recrystallization of the compound from acetone gave X-ray diffraction quality crystals of (I).

Refinement
All hydrogen atoms were fixed geometrically and allowed to ride on the parent carbon atoms with aromatic C-H = 0.93 Å, methylene C-H = 0.97 Å and methyl C-H = 0.96 Å. The displacement parameters were set as U iso (H) = 1.2-1.5 U eq (C).

Computing details
Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT-Plus (Bruker, 2004); data reduction: SAINT-Plus (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008  View of (I) showing the atomic numbering and 50% probability displacement ellipsoids [symmetry code: -x, y, 1/2 -z]. 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.