() and ()-1,4-Diphenyl-2-(2-phenyl-1-benzo[]imidazol-1-yl)but-2-ene-1,4-dione

The title compound C29H20N2O2 adopts and geometry about olefinic C14–C22 bond, where the benzoyl group at C22 and benzimidazole group at C14 lie on the opposite sides and on the same side across the olefinic bond, respectively. In configuration the phenyl groups of both benzoyl moieties are almost perpendicular to benzimidazole ring while the phenyl of benzimidazole at C7 is oriented at an angle of 30.76 (5)° to the mean plane of the benzimidazole ring. On the other hand in configuration the phenyl group at C7 of benzimidazole ring is oriented at an angle of 38.44 (7)° to the mean plane of the benzimidazole ring while the phenyl rings of benzoyl moieties at C15 and C23 lie at an angle of 16.07 (9)° and 40.29 (6)°, respectively, to the mean plane of the benzimidazole ring. The observed bond distances and bond angles fall within the normal accepted range of values. 1. Introduction Several examples of nitrogen containing nucleophilic addition to acetylenic ketones have been reported in the literature [1]. The reaction of primary and secondary amines with dibenzoylacetylene (DBA) are known to give enamine diones readily [2]. Heine et al. [3] have shown that diaziridines react with DBA at ambient temperature to give the corresponding 2-(alkylidenehydrazino)-1,4-diphenyl-2-butene-1,4-diones, arising through a Michael type of addition reaction. The reaction of dimethyl acetylenedicarboxylate (DMAD) with 2-aminobenzothiazole and 2-aminobenzimidazole has been earlier reported by Ogura et al. [4] to give 2-oxopyrimido[1,2-a]benzothiazole and 2-oxopyrimido[1,2-a]benzimidazole, respectively. Recently a series of imidazo[2,1-b]thiazole and benzo[ ]thiazolo[3,2-a]imidazole analogues were synthesized by the reaction of DBA with aminoimidazole and thiazole derivatives [5]. George and coworkers have earlier reported the reaction of imidazole, aziridine, and pyrazole derivatives with DBA yields a mixture of and isomeric adducts [6–8]. For example, the reaction 2-phenylbenzimidazole with dibenzoylacetylene has been shown to give and 1-imidozolyloyl-1,2-dibenzoylalkenes adducts [6]. The olefinic protons of these adducts are merged in the aromatic region; hence, it is difficult to assign the configuration of these isomers. Therefore single crystal X-ray analysis has been performed to differentiate the two isomers. 2. Experimental 2.1. Characterization Techniques Single crystal X-ray data sets were collected with a Bruker X8-Apex-II X-ray diffractometer. The melting points were recorded in an open capillary and are uncorrected. 2.2. Starting Material Dibenzoylacetylene (DBA)