4,4′-Dimeth­oxy-2,2′-{[(3aRS,7aRS)-2,3,3a,4,5,6,7,7a-octa­hydro-1H-1,3-benzimidazole-1,3-diyl]bis(methyl­ene)}diphenol

Augusto Rivera; Diego Quiroga; Jaime Ríos-Motta; Karla Fejfarová; Michal Dušek

doi:10.1107/S1600536811031436

. 2011 Aug 11;67(Pt 9):o2298–o2299. doi: 10.1107/S1600536811031436

4,4′-Dimethoxy-2,2′-{[(3aRS,7aRS)-2,3,3a,4,5,6,7,7a-octahydro-1H-1,3-benzimidazole-1,3-diyl]bis(methylene)}diphenol

Augusto Rivera ^a,^*, Diego Quiroga ^a, Jaime Ríos-Motta ^a, Karla Fejfarová ^b, Michal Dušek ^b

PMCID: PMC3200725 PMID: 22065834

Abstract

The title compound, C₂₃H₃₀N₂O₄, is a Mannich base useful for studying the effect of an electron-donating phenol substituent on intramolecular hydrogen bonding. In the molecular structure, the cyclohexane ring adopts a chair conformation and the five-membered ring has a twisted envelope conformation. Each methoxy group is oriented in the same plane of the respective aromatic ring, showing torsion angles below 11.8 (3)° and bond angles between the methoxy group and the aromatic ring of 116.6 (2) and 116.6 (1)°. The structure shows interactions between two the N atoms of the heterocyclic ring and the hydroxy groups by intramolecular O—H⋯N hydrogen-bonding interactions. In the crystal, C—H⋯O interactions are observed. The crystal studied was a racemic mixture of RR and SS enantiomers.

Related literature

For related structures, see: Rivera et al. (2010a ▶,b ▶). For the effect of the methoxy group on molecular structure, see: Özek et al. (2008 ▶); Ünver et al. (2009 ▶); Jamjah et al. (2011 ▶). For related quantum-chemical literature, see: Konschin (1984 ▶).

Experimental

Crystal data

C₂₃H₃₀N₂O₄
M _r = 398.5
Monoclinic,
a = 12.7693 (3) Å
b = 10.4365 (2) Å
c = 16.3229 (4) Å
β = 109.579 (3)°
V = 2049.53 (9) Å³
Z = 4
Cu Kα radiation
μ = 0.71 mm⁻¹
T = 120 K
0.51 × 0.14 × 0.02 mm

Data collection

Agilent Xcalibur diffractometer with an Atlas (Gemini ultra Cu) detector
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2010 ▶) T _min = 0.403, T _max = 1
23926 measured reflections
3216 independent reflections
2577 reflections with I > 3σ(I)
R _int = 0.055

Refinement

R[F ² > 2σ(F ²)] = 0.037
wR(F ²) = 0.105
S = 1.70
3216 reflections
268 parameters
2 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.19 e Å⁻³
Δρ_min = −0.17 e Å⁻³

Data collection: CrysAlis PRO (Agilent, 2010 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SIR2002 (Burla et al., 2003 ▶); program(s) used to refine structure: JANA2006 (Petříček et al. 2006 ▶); molecular graphics: DIAMOND (Brandenburg & Putz, 2005 ▶); software used to prepare material for publication: JANA2006.

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536811031436/nr2009sup1.cif

e-67-o2298-sup1.cif^{(23KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811031436/nr2009Isup2.hkl

e-67-o2298-Isup2.hkl^{(126.5KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811031436/nr2009Isup3.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
O1—H1⋯N2	0.89 (2)	1.90 (2)	2.709 (2)	151.1 (19)
O3—H3⋯N1	0.88 (2)	1.91 (2)	2.706 (2)	150.0 (19)
C8—H8A⋯O2ⁱ	0.96	2.55	3.427 (2)	152

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Symmetry code: (i) Inline graphic .

Acknowledgments

We acknowledge the Dirección de Investigaciones, Sede Bogotá (DIB) de la Universidad Nacional de Colombia, for financial support of this work, as well as the the Institutional research plan No. AVOZ10100521 of the Institute of Physics and the Praemium Academiae project of the Academy of Sciences of the Czech Republic. DQ acknowledges the Vicerrectoría Académica de la Universidad Nacional de Colombia for a fellowship.

supplementary crystallographic information

Comment

During our investigations on Mannich bases, we studied the effect of electron-withdrawing or electron-donating substituent of phenol on intramolecular hydrogen bond. Here we report the structure of the title compound (Fig. 1). The X-ray results of the title compound suggest an influence of the methoxy substituent in the hydrogen bonding interaction. The N···H distances and the N···O distances are longer (by about 0.07 Å and 0.05 Å, respectively), than the observed values in a related structure where the p-substituent is a chlorine atom (Rivera, et al. 2010b). However these values are in good agreement with the one found in the related structure where there are not p-substituents [N···H, 1.91 (2) Å; N···O, 2.6894 (14) Å] (Rivera et al., 2010a). Moreover, the observed C—O bond lengths [C10—O1, 1.377 (2) Å; C18—O3, 1.373 (2) Å] are longer in relation to the mentioned related structures [C—O, 1.364 (2) Å, C—O, 1.354 (2) Å] (Rivera et al., 2010a,b), which confirms the decreasing in the intermolecular hydrogen bonding interaction due the electronic influence of a electron-donating substituent as the methoxy group. The crystal packing (Figure 2) displays weak intermolecular C—H···O hydrogen bonds between neighboring molecules, which link them into 1D-chains.

In the crystal structure of the title compound, the cyclohexanediamine fragment adopts a chair conformation. The C—C—C bond angles within the cyclohexane ring are close to normal tetrahedral bond angles in a chair conformation since these values are in the range of 108.4 (2)° to 112.8 (2)°. The imidazolidine moiety has a twisted envelope conformation, indicating that the nitrogen lone pairs are oriented anti-axial to avoid repulsion electronic repulsions. In comparison with the values of the corresponding angles and bond distances in the phenol derivative (Rivera et al., 2010a), the C12—C13—O2 and C20—C21—O4 angles increase by 3.48° and 4.27° respectively, and the C9—C10 and C17—C18 bonds are the longest and the C10—C11 and C18—C19 bond are the shortest in the aromatic rings. These results suggest the existence of a distortion in the aromatic rings, which is present at the p-methoxyphenol moiety in some Schiff bases (Özek et al., 2008; Ünver et al., 2009; Jamjah et al., 2011), which could be explained by the presence of the OH and CH₃ groups, such as an STO-3G molecular orbital investigation suggested (Konschin, 1984), where molecular structure optimizations of methoxy-containing benzenes and related compounds indicated significant structural consequences in the aromatic rings by the presence of these substituents due their behavior as π donors and σ acceptors.

Experimental

To a solution of (2R,7R,11S,16S)-1,8,10,17-tetraazapentacyclo- [8.8.1.1^8,17.0^2,7.0^11,16]icosane (276 mg, 1.00 mmol) in dioxane (3 mL) and water (4 mL) in a two-necked round-bottomed flask, prepared beforehand following previously described procedures, was added dropwise a dioxane solution (3 mL) containing two equivalents of 4-methoxyphenol (248 mg, 2.00 mmol). The mixture was refluxed for about 8h. The solvent was evaporated under reduced pressure until a sticky residue appeared. The product was purified by chromatography on a silica column, and subjected to gradient elution with benzene:ethyl acetate (yield 34%, m.p. = 436–438 K). Single crystals of titlt compound were grown from a chloroform: methanol solution by slow evaporation of the solvent at room temperature over a period of about 2 weeks.