2-(5,6-Dihydro­benzimidazo[1,2-c]quinazolin-6-yl)phenol

Naser Eltaher Eltayeb; Siang Guan Teoh; Ching Kheng Quah; Hoong-Kun Fun

doi:10.1107/S1600536811030583

. 2011 Aug 6;67(Pt 9):o2243–o2244. doi: 10.1107/S1600536811030583

2-(5,6-Dihydrobenzimidazo[1,2-c]quinazolin-6-yl)phenol

Naser Eltaher Eltayeb ^a, Siang Guan Teoh ^b, Ching Kheng Quah ^c,^‡, Hoong-Kun Fun ^c,^*,^§

PMCID: PMC3200611 PMID: 22058910

Abstract

The asymmetric unit of the title compound, C₂₀H₁₅N₃O, contains two independent molecules, each of which is disordered over two sets of sites corresponding to a rotation of approximately 180° of the dihydrobenzimidazoquinazoline moiety, with refined site occupancies of 0.7479 (13) and 0.2521 (12) for both molecules. The pyrimidine rings are in sofa conformations. In one molecule, the hydroxy-substituted benzene ring forms dihedral angles of 83.9 (3) and 82.4 (4)° for the major and minor components, respectively, with the mean plane of the benzimidazole ring system. The corresponding dihedral angles in the other molecule are 88.31 (14) and 85.8 (6)°. In the crystal, molecules are linked via intermolecular O—H⋯N and N—H.·O hydrogen bonds into chains along [100].

Related literature

For general background to and the biological activity of benzimidazole compounds, see: Minoura et al. (2004 ▶); Pawar et al. (2004 ▶); Tomei et al. (2003 ▶); Barreca et al. (2003) ▶; Demirayak et al. (2002 ▶). For the synthesis, see: Eltayeb et al. (2011 ▶). For related structures, see: Eltayeb et al. (2007a ▶,b ▶,c ▶, 2009 ▶). For bond-length data, see: Allen et al. (1987 ▶). For ring conformations, see: Cremer & Pople (1975 ▶).

Experimental

Crystal data

C₂₀H₁₅N₃O
M _r = 313.35
Monoclinic,
a = 17.1513 (10) Å
b = 19.1160 (11) Å
c = 9.2630 (5) Å
β = 97.590 (1)°
V = 3010.4 (3) Å³
Z = 8
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 297 K
0.30 × 0.28 × 0.25 mm

Data collection

Bruker APEXII DUO CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.974, T _max = 0.978
40861 measured reflections
11057 independent reflections
8231 reflections with I > 2σ(I)
R _int = 0.047

Refinement

R[F ² > 2σ(F ²)] = 0.058
wR(F ²) = 0.158
S = 1.05
11057 reflections
625 parameters
144 restraints
H-atom parameters constrained
Δρ_max = 0.44 e Å⁻³
Δρ_min = −0.42 e Å⁻³

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT; data reduction: SAINT (Bruker, 2009 ▶); program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536811030583/lh5291sup1.cif

e-67-o2243-sup1.cif^{(49.5KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811030583/lh5291Isup2.hkl

e-67-o2243-Isup2.hkl^{(540.7KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811030583/lh5291Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1A—H1OA⋯N1Bⁱ	0.98	1.69	2.641 (3)	162
N3A—H3AB⋯O1Aⁱⁱ	0.86	2.50	3.241 (3)	144
O1B—H1OB⋯N1Aⁱⁱⁱ	0.97	1.79	2.686 (4)	151
N3B—H3BB⋯O1B^iv	0.86	2.15	2.974 (4)	160

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) .

Acknowledgments

The authors thank the Malaysian Government and Universiti Sains Malaysia for the RU research grant (1001/PKIMIA/815067). NEE thanks Universiti Sains Malaysia for a post-doctoral fellowship and the International University of Africa (Sudan) for providing study leave. The authors also thank Universiti Sains Malaysia for the Research University Grant No. 1001/PFIZIK/811160.

supplementary crystallographic information

Comment

The synthesis of benzimidazoles has received much attention owing to the varied biological activity such as antidiabetic (Minoura et al., 2004), antimicrobial, antifungal (Pawar et al., 2004), antiviral (Tomei et al., 2003), antiHIV (Barreca et al., 2003) and anticancer (Demirayak et al., 2002) properties exhibited by a number of derivatives of these compounds. Previously we reported the crystal structures of 4-allyl-2-[1-(5-allyl-2-hydroxy-3-methoxybenzyl) -1H-benzimidazol-2-yl]-6-methoxyphenol (Eltayeb et al., 2007a), 2-(2-methoxynaphthalen-1-yl)-1-[(2-methoxynaphthalen-1-yl)methyl] -1H-benzimidazole (Eltayeb et al., 2007b), 2-(benzimidazol-2-yl) -6-methoxyphenol (Eltayeb et al., 2007c) and 2-methoxy-6-(6-methyl -1H-benzimidazol-2-yl)phenol (Eltayeb et al., 2009). Considering the biological importance of the included benzimidazole ring, we describe in this paper the single crystal X-ray diffraction study of 2-(5,6- dihydrobenzimidazo[1,2-c]quinazolin-6-yl)phenol.

The asymmetric unit contains two independent molecules (Fig. 1), A and B. In each molecule, the benzimidazole fused ring system is disordered over two sets of sites with refined site occupancies of 0.748 (1) : 0.252 (1), suggesting 180° rotational disorder for the benzimidazole fused ring system. The conformations for pyrimidine rings are close to a sofa conformation (Cremer & Pople, 1975), puckering parameters Q = 0.330 (2) Å, Θ = 61.9 (3)° and φ = 277.5 (4)° (major component of molecule A), Q = 0.305 (12) Å, Θ = 120.6 (19)° and φ = 103.9 (19)° (minor component of molecule A), Q = 0.343 (3) Å, Θ = 60.4 (4)° and φ = 285.8 (4)° (major component of molecule B) and Q = 0.331 (11) Å, Θ = 119.3 (14)° and φ = 104.7 (14)° (minor component of molecule B). Bond lengths (Allen et al., 1987) and angles are within normal ranges. In molecule A (Fig. 2), the hydroxyphenyl ring (C15-C20) is almost perpendicular to the mean plane of benzimidazole ring (N1/N2/C1-C7) with the dihedral angles of 83.9 (3) and 82.4 (4)° for major and minor components, respectively. The corresponding dihedral angles for molecule B are 88.31 (14) and 85.8 (6)°.

In the crystal structure, Fig. 3, the molecules are linked via intermolecular O1A–H10A···N1Bⁱ, N3A–H3AB···O1Aⁱⁱ, O1B–H10B···N1Aⁱⁱⁱ and N3B–H3BB..O1B^iv hydrogen bonds (Table 1) into infinite one-dimensional chains along [100].

Experimental

The title compound was synthesized using Taha-Teoh's method (Eltayeb et al., 2011). To a solution of 2-(2-aminophenyl)-1H-benzimidazole (0.209 g, 1.0 mmol) in ethanol (30 mL) was added 2-hydroxybenzaldehyde (0.1 mL, 1.0 mmol). The color of the resulting solution is pale-yellow. Then on adding zinc chloride (0.136 g, 1.0 mmol), the color of the solution became golden-yellow. The mixture was refluxed with stirring for 3 h. Crystals suitable for XRD were formed after several days of slow evaporation of ethanol at room temperature.