4-Cyclo­butyl­amino-3-nitro­benzoic acid

Shivanagere Nagojappa Narendra Babu; Aisyah Saad Abdul Rahim; Hasnah Osman; Ching Kheng Quah; Hoong-Kun Fun

doi:10.1107/S1600536809021412

. 2009 Jun 13;65(Pt 7):o1566–o1567. doi: 10.1107/S1600536809021412

4-Cyclobutylamino-3-nitrobenzoic acid

Shivanagere Nagojappa Narendra Babu ^a, Aisyah Saad Abdul Rahim ^a,^‡, Hasnah Osman ^b, Ching Kheng Quah ^c,^§, Hoong-Kun Fun ^c,^*,^¶

PMCID: PMC2969240 PMID: 21582847

Abstract

The asymmetric unit of the title compound, C₁₁H₁₂N₂O₄, contains two crystallographically independent molecules with similar geometries. Both molecules contain an intramolecular N—H⋯O hydrogen bond. The dihedral angles between the benzene ring and the mean plane of the cyclobutane ring are 38.29 (7) and 57.04 (8)° in the two molecules, and the nitro group is twisted slightly away from the plane of the benzene ring [dihedral angles = 9.15 (12) and 9.55 (12)° in the two molecules]. In the crystal, the independent molecules are linked into dimers by O—H⋯O hydrogen bonds between their carboxyl groups, and C—H⋯O and C—H⋯π interactions are formed between dimers.

Related literature

For the biological activity of benzimidazole derivatives, see: Wright (1951 ▶); Singh et al. (2009 ▶). For details of the synthesis, see: Narendra Babu et al. (2009a ▶,b ▶); Ishida et al. (2006 ▶).

Experimental

Crystal data

C₁₁H₁₂N₂O₄
M _r = 236.23
Triclinic,
a = 9.8555 (2) Å
b = 10.5308 (2) Å
c = 10.9110 (2) Å
α = 74.860 (1)°
β = 78.265 (1)°
γ = 84.826 (1)°
V = 1069.44 (4) Å³
Z = 4
Mo Kα radiation
μ = 0.11 mm⁻¹
T = 110 K
0.37 × 0.23 × 0.21 mm

Data collection

Bruker SMART APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.960, T _max = 0.976
29344 measured reflections
7670 independent reflections
6094 reflections with I > 2σ(I)
R _int = 0.027

Refinement

R[F ² > 2σ(F ²)] = 0.048
wR(F ²) = 0.139
S = 1.05
7670 reflections
315 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.68 e Å⁻³
Δρ_min = −0.25 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT (Bruker, 2005 ▶); data reduction: SAINT; 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 datablocks global, I. DOI: 10.1107/S1600536809021412/bi2372sup1.cif

e-65-o1566-sup1.cif^{(24.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809021412/bi2372Isup2.hkl

e-65-o1566-Isup2.hkl^{(375.2KB, hkl)}

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
O2A—H1OA⋯O1Bⁱ	0.81	1.76	2.5608 (13)	166
O2B—H1OB⋯O1Aⁱⁱ	0.83	1.89	2.7118 (12)	170
N2A—H1NA⋯O4A	0.89 (2)	1.93 (2)	2.6332 (13)	135.3 (17)
N2B—H1NB⋯O4B	0.80 (2)	2.05 (2)	2.6432 (13)	130.7 (18)
C8B—H8BB⋯O4Aⁱⁱⁱ	0.97	2.54	3.4613 (16)	158
C8B—H8BA⋯Cg1^iv	0.97	2.83	3.4744 (13)	124

Open in a new tab

Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) . Cg1 is the centroid of the C1B–C6B benzene ring.

Acknowledgments

SNNB, ASAR and HO are grateful to Universiti Sains Malaysia (USM) for funding the synthetic chemistry work under the University Research Grant (1001/PFARMASI/815026). SNNB acknowledges USM for a Postdoctoral Research Fellowship. HKF and CKQ thank USM for the Research University Golden Goose Grant (1001/PFIZIK/811012). CKQ thanks USM for a Research Fellowship.

supplementary crystallographic information

Comment

Multi functionalized benzimidazole remains as an attractive scaffold to display essential binding moieties against many validated biological targets (Wright, 1951; Singh et al., 2009). This heterocycle is commonly accessed via nitro benzoic acid derivatives, which form a part of our current synthetic chemistry work (Narendra Babu et al., 2009a&b; Ishida et al., 2006). Recently, we have successfully synthesized the title compound, whose crystal structure is described here.

The asymmetric unit contains two crystallographically independent molecules (Fig. 1), A and B with similar geometries. An intramolecular N–H···O hydrogen bond is formed in both independent molecules. The dihedral angle formed by the C1A–C6A benzene ring and C7A–C10A cyclobutane is 38.29 (7)° and that between the C1B–C6B benzene ring and C7B–C10B cyclobutane is 57.04 (8)°. The nitro group in each molecule is slightly twisted away from the attached benzene ring as indicated by the torsion angle O3—N1—C1—C2, being 7.97 (15)° and 7.80 (14)° in molecules A and B, respectively.

The crystal packing (Fig. 2) is consolidated by intermolecular O—H···O and C—H···O hydrogen bonds. Molecules are linked by O—H···O hydrogen bonds between their carboxylate groups to form dimers. The crystal structure is further stabilized by C—H···π (Table 1) interactions involving the C1B–C6B benzene ring (centroid Cg1) and short O4B···O4B contacts (symmetry code: 2 - x, 1 - y, 1 - z) with distance = 2.8957 (12) Å which is shorter than the sum of van der Waals radii of the O atoms.

Experimental

The title compound was obtained by refluxing ethyl 4-(cyclobutylamino)-3-nitro-benzoate (0.2 g, 0.0007 mol) and KOH (0.08 g, 0.0015 mol) in aqueous ethanol (5 ml) for 3 h. After completion of the reaction, ethanol was distilled off and the reaction mixture was diluted with water (5 ml). The aqueous layer was washed with dichloromethane (2 × 5 ml) and acidified with concentrated hydrochloric acid to afford a yellow solid. Yellow crystals suitable for X-ray analysis were obtained after recrystallization of the crude product with hot ethyl acetate.