4-(5,6-Dihydrobenzimidazo[1,2-c]quinazolin-6-yl)benzene-1,3-diol dimethyl sulfoxide monosolvate

In the title solvated benzimidazole compound, C20H15N3O2·C2H6OS, both the benzimidazole fused-ring system and the complete dimethyl sulfoxide solvent molecule are disordered over two sets of sites, in 0.750 (5):0.250 (5) and 0.882 (4):0.118 (4) ratios, respectively. The conformation of the pyrimidine ring is close to a half-chair for the major disorder component, whereas for the minor component it is close to a boat. The dihydroxyphenyl ring is almost perpendicular to the mean plane of the benzimidazole ring [dihedral angle = 87.3 (2)° for the major disorder component and 88.3 (5)° for the minor disorder component]. In the crystal, molecules are linked into layers parallel to (110) by O—H⋯N and C—H⋯O hydrogen bonds. A bifurcated O—H⋯(O,S) bond links the benzimidazole and solvent molecules.

In the title solvated benzimidazole compound, C 20 H 15 N 3 O 2 Á-C 2 H 6 OS, both the benzimidazole fused-ring system and the complete dimethyl sulfoxide solvent molecule are disordered over two sets of sites, in 0.750 (5):0.250 (5) and 0.882 (4):0.118 (4) ratios, respectively. The conformation of the pyrimidine ring is close to a half-chair for the major disorder component, whereas for the minor component it is close to a boat. The dihydroxyphenyl ring is almost perpendicular to the mean plane of the benzimidazole ring [dihedral angle = 87.3 (2) for the major disorder component and 88.3 (5) for the minor disorder component]. In the crystal, molecules are linked into layers parallel to (110) by O-HÁ Á ÁN and C-HÁ Á ÁO hydrogen bonds. A bifurcated O-HÁ Á Á(O,S) bond links the benzimidazole and solvent molecules.

Related literature
For related structures and background to benzimidazoles, see: Eltayeb et al. (2007aEltayeb et al. ( ,b,c, 2009. For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986). For ring conformations, see: Cremer & Pople (1975 Table 1 Hydrogen-bond geometry (Å , ). The benzimidazole fused ring system in (I) is disordered over two sets of sites with refined site occupancies of 0.750 (5) and 0.250 (5). The solvent molecule is also disordered over two orientations with refined site occupancies of 0.882 (4) and 0.118 (4). The conformation for pyrimidine ring is close to a half-chair conformation for major component whereas for minor component it is close to a boat conformation (Cremer & Pople, 1975). The dihydroxyphenyl ring is almost perpendicular to the mean plane of benzimidazole ring (N1A/C1A-C6A/N2A/C7A) with the dihedral angle of 87.3 (2)° whereas this angle is 88.3 (5)° for minor component. In the crystal structure, the molecules are linked into infinite one-dimensional chains along a axis by intermolecular O2-H1O2···N2A hydrogen bonds and the intermolecular C11A-H11A···O2 hydrogen bonds (Table 1) further linked these chains into planes parallel to ab plane (Fig. 3). The benzimidazole molecule and the solvent molecule is stabilized by the O1-H1O1···S1A and O1-H1O1···O3A interactions (Table 1).

Experimental
To a solution of 2-(2-aminophenyl)-1H-benzimidazole (0.209 g, 1.0 mmol) in ethanol (30 ml) was added 2,4-dihydroxybenzaldehyde (0.138 g, 1.0 mmol). The color of the resulting solution is pale-pink. Then on adding zinc chloride (0.136 g, 1.0 mmol), the color of solution changed to yellowish-pink. The mixture was refluxed with stirring for 3 hours. The product (yellow precipitate) was obtained by evaporation of the solvent under reduced pressure using a rotary evaporator. Yellow blocks of (I) were formed after several days of slow evaporation of an acetone solution layered with a small amount of dimethylsulfoxide at room temperature.

Refinement
All disordered components were subjected to rigid bond and similarity restraints. All minor disordered components were refined isotropically. The O-bound hydrogen atoms were located from difference Fourier map and refined as riding on their parent atom, with U iso (H) = 1.5 U eq (O). The rest of the hydrogen atoms were positioned geomatrically [C-H = 0.93-0.98 Å; N-H = 0.86 Å] and refined using a riding model, with U iso (H) = 1.2 or 1.5 U eq (C,N or C methyl ). A rotating-group model were applied for methyl groups.
supplementary materials sup-2 Figures Fig. 1. The molecular structure of (I) with 30% probability ellipsoids for non-H atoms. Only major disordered component is shown.    (2)