N-(3-Bromo-1,4-dioxo-1,4-dihydro-2-naphthyl)-2-chloro-N-(2-chlorobenzoyl)benzamide

The title compound, C24H12BrCl2NO4, was synthesized from 2-amino-3-bromo-1,4-naphthoquinone and 2-chlorobenzoyl chloride. The crystal structure shows that each of the chlorophenyl rings is inclined at about 60° to the naphthoquinone ring system. The two chlorophenyl rings adopt a conformation that ensures that chlorine substituents are anti so as to reduce electronic repulsion. An examination of the packing shows close O⋯Br and Cl⋯Cl contacts of 2.947 (2) and 3.346 (1) Å, respectively. In addition, the molecules are linked by weak intermolecular C—H⋯O and C—H⋯Cl interactions.

RJB acknowledges the NSF-MRI program (grant No. CHE-0619278) for funds to purchase the X-ray diffractometer.
Each of the phenyl groups is inclined at about 60° to the naphthoquinone ring of the titled compound C 24 H 12 BrCl 2 NO 4 .
The two chlorophenyl rings adopt a conformation that ensures that chlorine substituents are anti to each other so as to reduce electronic repulsion. An examination of the packing shows close contacts between O1A and Br at (1/2 -x, 1/2 + y, 3/2 -z) (2.947 (2) Å) and Cl1A and Cl1B at (x, 1 + y, z) (3.346 (1) Å). The explanation of these close contacts lies in a balance between the torsion angles subtended at the N which balances short intramolecular contacts against short intermolecular contacts and comes up with the best compromise.

Experimental
To a solution of 2-amino-3-bromo-1,4-naphthoquinone (300 mg, 1.21 mmol) in dry THF was added NaH (72.6 mg 3.025 mmol) and the mixture was stirred for 15 minutes. 2-Chloro-benzoylchloride (0.37 ml) was added thereafter and this mixture was stirred at room temperature for 16-24 hr under argon. The solvent was removed in vacuo and the solid residue was dissolved in dichloromethane (40 ml). The resultant solution was washed with water (3 x 15 ml), saturated NaCl solution (2 x 15 ml) and dried over anhydrous magnesium sulfate. The solvent was removed in vacuo and the residue triturated in ethyl acetate to give a yellow solid (280.0 g m). This was recrystallized in ethyl acetate to furnish the title imide (214.2 mg, 34%).

Refinement
All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with C-H distances of 0.95 Å and U iso (H) = 1.2U eq (C).