2-Bromo-5-tert-butyl-N-methyl-N-[2-(methyl­amino)­phen­yl]-3-(1-methyl-1H-benzimidazol-2-yl)benzamide

Poonam Rajesh Prasad; Shikha Das; Harkesh B Singh; Ray J Butcher

doi:10.1107/S1600536814014433

. 2014 Jun 25;70(Pt 7):o822–o823. doi: 10.1107/S1600536814014433

2-Bromo-5-tert-butyl-N-methyl-N-[2-(methylamino)phenyl]-3-(1-methyl-1H-benzimidazol-2-yl)benzamide

Poonam Rajesh Prasad ^a, Shikha Das ^a, Harkesh B Singh ^a, Ray J Butcher ^b,^*

PMCID: PMC4120529 PMID: 25161598

Abstract

In the title compound, C₂₇H₂₉BrN₄O, benzimidazole ring system and the amide moiety are planar [r.m.s. deviations = 0.016 (2) and 0.017 (1) Å, respectively]. The molecule adopts a conformation in which the amide linkage is almost perpendicular to the central ring [dihedral angle = 85.79 (8)°], while the benzimidazole ring system makes a dihedral angle of 70.26 (11)° with the central ring. In the crystal, the molecules form dimers through N—H⋯O hydrogen bonds and C—H⋯O interactions. These dimers are further linked into zigzag ribbons along [201] by weak C—H⋯Br interactions. As a result of the bulky nature of the molecule, as evidenced by the large dihedral angles between rings, there is little evidence for any π–π interactions.

Keywords: crystal structure

Related literature

The metal binding properties of imidazole-containing pincer ligands can be modified by the type of donor atoms and the electron-withdrawing and electron-releasing character of their substituents, see: Selander & Szabó (2011 ▶). For the effect of N-substitution on the catalytic activity of phosphinoimidazolines in palladium-catalysed Heck reactions, see: Busacca et al. (2003 ▶). For the use of bromine-substituted benzimidazole in Heck reactions, see: Reddy & Krishna (2005 ▶). For standard bond lengths, see: Allen et al. (1987 ▶). For the preparation of the precursor, 2-bromo-5-(tert-butyl)isophthalic acid, see: Field et al. (2003 ▶). graphic file with name e-70-0o822-scheme1.jpg

Experimental

Crystal data

C₂₇H₂₉BrN₄O
M _r = 505.45
Monoclinic,
a = 34.4327 (13) Å
b = 9.4152 (2) Å
c = 17.1092 (7) Å
β = 118.312 (5)°
V = 4883.2 (3) Å³
Z = 8
Cu Kα radiation
μ = 2.50 mm⁻¹
T = 123 K
0.38 × 0.32 × 0.23 mm

Data collection

Agilent Xcalibur Ruby Gemini diffractometer
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012 ▶) T _min = 0.788, T _max = 1.000
9307 measured reflections
4929 independent reflections
4100 reflections with I > 2σ(I)
R _int = 0.028

Refinement

R[F ² > 2σ(F ²)] = 0.034
wR(F ²) = 0.093
S = 1.03
4929 reflections
308 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.43 e Å⁻³
Δρ_min = −0.35 e Å⁻³

Data collection: CrysAlis PRO (Agilent, 2012 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablock(s) I. DOI: 10.1107/S1600536814014433/jj2190sup1.cif

e-70-0o822-sup1.cif^{(24.8KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536814014433/jj2190Isup2.hkl

e-70-0o822-Isup2.hkl^{(241.5KB, hkl)}

Click here for additional data file.^{(9KB, cml)}

Supporting information file. DOI: 10.1107/S1600536814014433/jj2190Isup3.cml

CCDC reference: 1009070

Additional supporting information: crystallographic information; 3D view; checkCIF report

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N3—H3B⋯O1ⁱ	0.81 (3)	2.35 (3)	3.038 (3)	143 (3)
C4—H4A⋯Brⁱⁱ	0.95	2.98	3.719 (3)	135
C12—H12A⋯O1ⁱ	0.95	2.37	3.287 (3)	163

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

Acknowledgments

RJB acknowledges the NSF MRI program (grant No. CHE-0619278) for funds to purchase an X-ray diffractometer.

supplementary crystallographic information

S1. Experimental

The methylation reaction of 2 (Fig. 1) was carried out by reacting 1 (0.5 g, 1.12 mmol) with an excess of methyl iodide (1.75 g, 10 eq), followed by the addition of KOH (0.125 g, 2.24 mmol) in dry acetone (20 mL) and some molecular sieves. The reaction mixture was refluxed for 2 h. Then, it was diluted with ethyl acetate and washed with water. The organic layer was dried over Na₂SO₄ and purified by column chromatography to afford 2 which was crystallized from a mixture of dichloromethane and ether. Anal. Calcd. for C₂₇H₂₉BrON₄: C, 64.16; H, 5.78; N, 11.08; found C, 64.30; H, 6.22; N, 9.17.

S1.1. Refinement

H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with a C—H distances of 0.95 and 0.98 Å U_iso(H) = 1.2U_eq(C) and 0.96 Å for CH₃ [U_iso(H) = 1.5U_eq(C)]. The hydrogen atom attached to N3 was located in a difference Fourier and refined isotropically.

S2. Comment

The presence of imidazole rings in any molecular framework provides excellent modification sites for the fine tuning of properties related to electronic and steric factors. It has been reported in the literature that the strong electronic effect can be modified by the type of donor atoms and the electron-withdrawing and electron-releasing character of their substituents (Selander, & Szabó, 2011). Recently the effect of N-substitution on the catalytic activities of phosphinoimidazolines in palladium catalyzed Heck reactions has been reported (Busacca et al., 2003). Later, Reddy and co-workers (Reddy, & Krishna, 2005) have studied the use of bromine substituted benzimidazole in Heck reactions. Pincer ligands have immense scope in exploring different types of metal coordination chemistry and stabilizing unusual species. They provide the sites which can be easily fine tuned to synthesize a number of metal complexes/species, which can be stabilized by three coordinating/bonding units of the pincer ligands. There are no examples of selenium containing benzimidazoles known in the literature. Therefore, 2, 2'-(2-bromo-5-(tert-butyl)-1,3-diyl)bis(1H-benzimidazole) (1) and its derivatives, having two coordinating imidazole rings were designed to incorporate selenium at 2-position of the phenyl group. An attempted methylation of 1 led to cleavage of the one of the benzimidazole rings and resulted in the formation of unexpected compound 2 (Fig. 1). 2-Bromo-5-(tert-butyl)isophthalic acid, the precursor for synthesizing 1, was prepared according to literature procedure (Field, et al., 2003). Compound 1 was synthesized by the reaction of 2-bromo-5-tert-butyl-isophthalic acid with 1,2-phenylenediamine in polyphosphoric acid at 240°C.

In view of the above, the structure of the title compound, C₂₇H₂₉BrN₄O, was determined (Fig. 2). The bond lengths and angles are all in the expected ranges (Allen et al., 1987) for such compounds. All the aromatic groups and the amide moiety are planar (rms deviations of 0.006 (1), 0.008 (2), 0.016 (2), and 0.017 (1) for the central phenyl ring, the substituent phenyl ring, the benzimidazole ring, and the amide moiety, respectively). The molecule adopts a conformation where the amide linkage is almost perpendicular to the central ring with a dihedral angle of 85.79 (8)° between central ring (C9–C14) and amide moiety (C19/C20/C21/N4/O1) while the benzimidazole ring makes a dihedral angle of 70.26° with the central ring. The molecules form dimers through N3—H···O1 intermolecular hydrogen bonds (Fig. 3). These dimers are further linked into zig-zag ribbons in the [2 0 1] direction by weak C—H···Br interactions. Because of the bulky nature of the molecule, as evidenced by the large dihedral angles between rings, there is little evidence for any π–π interactions.