Reaction of o-aminophenylbenzimidazole with p-dimethylaminobenzaldehyde yielded 6-p-dimethylaminophenyl-5,6-dihydrobenzoimidazo[1,2-c]quinazoline, which was characterized by elemental analysis, IR, UV-Vis, 1 H NMR, 13 C NMR, mass spectral studies and X-ray crystal structure analysis. Studies on the antimicrobial activity of the compound revealed that it is active against fungus Yeast but not Bacillus subtilis. The compound crystallized in the space group P2 1 /n with the unit cell parameters a = 10.652(2) Å , b = 11.002(2) Å , c = 15.753(2) Å , b = 109.29(2)°and the structure was refined to an R-factor of 0.0479. The hydropyrimidine ring in the quinazoline moiety is in skew-boat conformation. The dimethylamino group attached to phenyl ring is in conjugation with it. The structure was stabilized by intermolecular C-H-N interactions. A few of the related quinazolines (6-p-hydroxyphenyl-5,6-dihydrobenzoimidazo [1,2-c]quinazoline; 6-phenyl-5,6-dihydrobenzoimidazo[1,2-c]quinazoline; 6-pyridyl-5,6-dihydrobenzoimidazo[1,2-c]quinazoline; 6-furyl-5,6-dihydrobenzoimidazo[1,2-c]quinazoline) were also examined for their biological activity, in addition to their characterization by IR, UV-Vis, 1 H and 13 C NMR spectral studies along with structural comparison.

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Quinazolines form an important class of heterocyclic compounds that receive a considerable amount of interest in the field of medicinal chemistry.Some of the compounds containing the quinazoline moiety show fungicidal, antimicrobial, CNS-dependent, anti-cancer, anti-hypertensive 1 and anti-HIV activities. 2 Some derivatives of indole[1,2c]quinazoline show cataleptogenic activity. 3 A structure analysis provides an opportunity to study biological activity and its implication in the structural requirement needed for binding to the receptors. The present study was undertaken in order to study the influence of the substituent groups on the conformation of the quinazoline ring system, which also forms a part of our continuing study of biologically active compounds. In view of the above, we report herein the synthesis and crystal structure of the title compound.A mixture of o-aminophenylbenzimidazole (0.05 mol, 10.45 g) and valeraldehyde (0.05 mol, 4.31 g) was refluxed in 200 ml of alcohol for 5 h. The resulting solution was concentrated under reduced pressure to a small volume to obtain a yellow compound. It was filtered and recrystallized from alcohol to obtain a cream-colored crystalline compound (yield 60%; melting point 120˚C). A schematic diagram of the molecule is shown in Fig. 1.A single crystal of the title compound with dimensions 0.3 × 0.27 × 0.25 mm was chosen for an X-ray diffraction study. The data were collected on a DIPLabo Image Plate system with graphite-monochromated Mo Kα radiation. Thirty six frames of data were collected by the oscillation method. Each exposure of the image plage was set to a period of 400 s. Successive frames were scanned in steps of 5˚ per min with an oscillation range of 5˚. Image processing and data reduction were performed using Denzo. 4 All of the frames could be indexed using a primitive monoclinic lattice. The details of the crystal data and refinement are given in Table 1. x185 ANALYTICAL SCIENCES 2006, VOL. 22 X-ray Structure Analysis OnlineThe title compound was synthesized and the structure was investigated by X-ray crystallography. The compound crystallizes in the monoclinic crystal class in the space group P21/n with cell parameters a = 7.6800(6)Å, b = 17.3330(15)Å, c = 12.0440(8)Å, β = 105.248(5)˚, Z = 4. The quinazoline ring is in envelope conformation. The structure exhibits an intermolecular hydrogen bond of the type N-H·N.