organic compounds
Ethyl 1-(butan-2-yl)-2-(2-methoxyphenyl)-1H-benzimidazole-5-carboxylate
aSchool of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 USM Penang, Malaysia, bKulliyyah of Science, International Islamic University Malaysia, Bandar Indera Mahkota, 25200 Kuantan, Pahang, Malaysia, and cSchool of Chemical Sciences, Universiti Sains Malaysia, 11800 USM Penang, Malaysia
*Correspondence e-mail: aisyah@usm.my
In the title compound, C21H24N2O3, the mean planes of the benzene ring and the benzimidazole ring system form a dihedral angle of 69.94 (7)°. The ethyl group atoms of the ethanoate fragment are disordered over two sets of sites, with refined occupancies of 0.742 (6) and 0.258 (6). In the crystal, there are weak C—H⋯N hydrogen bonds which connect molecules into chains along the b axis. A weak intermolecular C—H⋯π interaction is also observed.
Related literature
For the synthesis and a closely related structure, see: Arumugam et al. (2010). For background to microwave chemistry, see: Kappe & Dallinger (2006); Hamzah et al. (2011). For the synthesis of benzimidazole derivatives and their applications, see: Wang et al. (2011); VanVliet et al. (2005); Loupy (2002); Santagada et al. (2001); Nicolaou et al. (2000); Evans et al. (1988). For standard bond lengths, see: Allen et al. (1987).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2009); cell SAINT (Bruker, 2009); 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).
Supporting information
https://doi.org/10.1107/S1600536811046095/lh5357sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536811046095/lh5357Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S1600536811046095/lh5357Isup3.cml
The title compound was prepared according to our previous procedure (Arumugam et al., 2010). A solution of the sec-butyl phenylene diamine (1.0 mmol) and sodium bisulfite adduct of 2-methoxybenzaldehyde (3.5 mmol) in DMF was heated under focused microwave conditions at 403K for 2 minutes. The reaction mixture was diluted in EtOAc (20 ml) and washed with H2O (20 ml). The organic layer was pooled together, dried over Na2SO4, and then removed in vacuo. Recrystallization with ethyl acetate gave the title compound as colourless crystals.
All atoms were position geometrically and refined using a riding model, with C—H = 0.93–0.97 Å and Uiso(H)= 1.2 or 1.5Ueq(C). The atoms C20 and C21 are disordered over two sites with site occupancies of 0.742 (6) and 0.258 (2). A rigid body restraint (DELU in SHELXL (Sheldrick, 2008)) was applied for atoms C17 and C18. A rotating group model was applied to the non-disordered methyl groups.
Microwave-assisted synthesis of heterocycles proves to be an invaluable technology in the fields of medicinal chemistry and drug discovery (Kappe & Dallinger, 2006). The utility of high-speed microwave chemistry is evident from the reported synthesis of privileged structures (Evans et al., 1988; Nicolaou et al., 2000) such as benzodiazepine (Santagada et al., 2001), indoles (Loupy, 2002) and benzimidazoles (Wang et al., 2011; VanVliet et al., 2005). As a part of our on-going work in benzimidazole synthesis under microwave conditions (Hamzah et al., 2011), we present herein the X-ray
of the title compound.The molecular structure of the title compound (Fig. 1) is similiar to the previously reported ethyl 1-sec-butyl-2-(4-methoxyphenyl) -1H-benzimidazole-5-carboxylate (Arumugam et al., 2010) in that only the position of the methoxy group is different. The benzene [C8—C13] ring and benzimidazole ring system [N1/N2/C1-C7] are essentially planar with maximum deviation of 0.050 (1)Å for atom N2. The mean-planes of the rings form a dihedral angle of 69.94 (7)°. The bond lengths (Allen et al., 1987) and angles aree in the normal ranges and comparable to those in para-methoxy derivative. The ethyl atoms (C20 & C21) of ethanoate fragment are disordered over two positions with refined site occupancies of 0.742 (6) and 0.258 (6). In the crystal, a C12—H12···N1i hydrogen bond connects molecules to form a zigzag chain propagating along the b axis (Fig. 2). An weak intermolecular C20A—H20C···Cgii (minor component of disorder) interaction is also observed; Cg1 is the centroid of N1/N2/C1/C2/C7.
For the synthesis and a closely related structure, see: Arumugam et al. (2010). For background to microwave chemistry, see: Kappe & Dallinger (2006); Hamzah et al. (2011). For the synthesis of benzimidazole derivatives and their applications, see: Wang et al. (2011); VanVliet et al. (2005); Loupy (2002); Santagada et al. (2001); Nicolaou et al. (2000); Evans et al. (1988). For standard bond lengths, see: Allen et al. (1987).
Data collection: APEX2 (Bruker, 2009); cell
SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).C21H24N2O3 | F(000) = 752 |
Mr = 352.42 | Dx = 1.190 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 8039 reflections |
a = 10.6746 (3) Å | θ = 2.1–25.0° |
b = 12.3344 (4) Å | µ = 0.08 mm−1 |
c = 15.6158 (5) Å | T = 296 K |
β = 106.901 (1)° | Block, colourless |
V = 1967.25 (11) Å3 | 0.52 × 0.44 × 0.32 mm |
Z = 4 |
Bruker SMART APEXII CCD area-detector diffractometer | 3475 independent reflections |
Radiation source: fine-focus sealed tube | 2712 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.025 |
Detector resolution: 83.66 pixels mm-1 | θmax = 25.0°, θmin = 2.1° |
φ and ω scan | h = −11→12 |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | k = −11→14 |
Tmin = 0.959, Tmax = 0.975 | l = −18→17 |
17688 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.045 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.122 | H-atom parameters constrained |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0526P)2 + 0.5324P] where P = (Fo2 + 2Fc2)/3 |
3475 reflections | (Δ/σ)max < 0.001 |
245 parameters | Δρmax = 0.35 e Å−3 |
3 restraints | Δρmin = −0.18 e Å−3 |
C21H24N2O3 | V = 1967.25 (11) Å3 |
Mr = 352.42 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 10.6746 (3) Å | µ = 0.08 mm−1 |
b = 12.3344 (4) Å | T = 296 K |
c = 15.6158 (5) Å | 0.52 × 0.44 × 0.32 mm |
β = 106.901 (1)° |
Bruker SMART APEXII CCD area-detector diffractometer | 3475 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | 2712 reflections with I > 2σ(I) |
Tmin = 0.959, Tmax = 0.975 | Rint = 0.025 |
17688 measured reflections |
R[F2 > 2σ(F2)] = 0.045 | 3 restraints |
wR(F2) = 0.122 | H-atom parameters constrained |
S = 1.05 | Δρmax = 0.35 e Å−3 |
3475 reflections | Δρmin = −0.18 e Å−3 |
245 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
O1 | 0.22019 (14) | 0.60261 (11) | 0.83252 (9) | 0.0694 (4) | |
O2 | 0.16647 (18) | 1.12078 (12) | 1.21044 (10) | 0.0894 (5) | |
O3 | 0.10964 (19) | 1.17279 (12) | 1.06857 (10) | 0.0917 (5) | |
N1 | 0.29480 (16) | 0.88252 (11) | 0.90695 (9) | 0.0562 (4) | |
N2 | 0.36352 (14) | 0.74369 (11) | 1.00207 (8) | 0.0475 (3) | |
C1 | 0.34617 (16) | 0.78558 (13) | 0.91776 (10) | 0.0467 (4) | |
C2 | 0.32104 (16) | 0.82294 (12) | 1.04995 (10) | 0.0445 (4) | |
C3 | 0.31600 (18) | 0.82949 (14) | 1.13790 (11) | 0.0551 (5) | |
H3 | 0.3450 | 0.7729 | 1.1781 | 0.066* | |
C4 | 0.26638 (18) | 0.92316 (14) | 1.16254 (11) | 0.0542 (4) | |
H4 | 0.2638 | 0.9304 | 1.2213 | 0.065* | |
C5 | 0.21963 (17) | 1.00806 (13) | 1.10246 (11) | 0.0496 (4) | |
C6 | 0.22494 (19) | 1.00099 (13) | 1.01515 (11) | 0.0540 (5) | |
H6 | 0.1942 | 1.0572 | 0.9748 | 0.065* | |
C7 | 0.27727 (17) | 0.90788 (13) | 0.98941 (10) | 0.0473 (4) | |
C8 | 0.38804 (17) | 0.72852 (14) | 0.84697 (10) | 0.0498 (4) | |
C9 | 0.49117 (19) | 0.76994 (16) | 0.82051 (12) | 0.0606 (5) | |
H9 | 0.5345 | 0.8316 | 0.8484 | 0.073* | |
C10 | 0.5308 (2) | 0.72096 (19) | 0.75319 (13) | 0.0711 (6) | |
H10 | 0.6003 | 0.7493 | 0.7358 | 0.085* | |
C11 | 0.4666 (2) | 0.63017 (18) | 0.71234 (13) | 0.0694 (6) | |
H11 | 0.4939 | 0.5966 | 0.6675 | 0.083* | |
C12 | 0.3627 (2) | 0.58773 (16) | 0.73630 (11) | 0.0608 (5) | |
H12 | 0.3196 | 0.5264 | 0.7076 | 0.073* | |
C13 | 0.32254 (18) | 0.63726 (14) | 0.80372 (11) | 0.0517 (4) | |
C14 | 0.1359 (2) | 0.52171 (19) | 0.78162 (15) | 0.0819 (6) | |
H14A | 0.0981 | 0.5473 | 0.7216 | 0.123* | |
H14B | 0.0675 | 0.5063 | 0.8084 | 0.123* | |
H14C | 0.1852 | 0.4569 | 0.7805 | 0.123* | |
C15 | 0.42814 (19) | 0.63962 (14) | 1.03579 (12) | 0.0601 (5) | |
H15 | 0.4483 | 0.6042 | 0.9852 | 0.072* | |
C16 | 0.3357 (2) | 0.56259 (16) | 1.06687 (15) | 0.0782 (6) | |
H16A | 0.3108 | 0.5957 | 1.1151 | 0.117* | |
H16B | 0.3800 | 0.4955 | 1.0869 | 0.117* | |
H16C | 0.2589 | 0.5488 | 1.0179 | 0.117* | |
C17 | 0.5563 (2) | 0.65788 (19) | 1.10606 (15) | 0.0816 (6) | |
H17A | 0.5395 | 0.6900 | 1.1583 | 0.098* | |
H17B | 0.5984 | 0.5884 | 1.1238 | 0.098* | |
C18 | 0.6475 (2) | 0.7294 (2) | 1.07565 (18) | 0.1013 (8) | |
H18A | 0.6583 | 0.7017 | 1.0208 | 0.152* | |
H18B | 0.7308 | 0.7312 | 1.1206 | 0.152* | |
H18C | 0.6120 | 0.8014 | 1.0660 | 0.152* | |
C19 | 0.1636 (2) | 1.10442 (15) | 1.13428 (13) | 0.0599 (5) | |
C20 | 0.0550 (11) | 1.2722 (4) | 1.0931 (10) | 0.103 (2) | 0.742 (6) |
H20A | −0.0207 | 1.2560 | 1.1134 | 0.124* | 0.742 (6) |
H20B | 0.1196 | 1.3091 | 1.1409 | 0.124* | 0.742 (6) |
C21 | 0.0176 (5) | 1.3391 (3) | 1.0141 (4) | 0.1145 (15) | 0.742 (6) |
H21A | −0.0225 | 1.4045 | 1.0269 | 0.172* | 0.742 (6) |
H21B | −0.0436 | 1.3005 | 0.9667 | 0.172* | 0.742 (6) |
H21C | 0.0938 | 1.3571 | 0.9963 | 0.172* | 0.742 (6) |
C21A | 0.0967 (16) | 1.3540 (11) | 1.0711 (11) | 0.1145 (15) | 0.258 (6) |
H21D | 0.0569 | 1.4175 | 1.0873 | 0.172* | 0.258 (6) |
H21E | 0.0936 | 1.3581 | 1.0091 | 0.172* | 0.258 (6) |
H21F | 0.1863 | 1.3495 | 1.1073 | 0.172* | 0.258 (6) |
C20A | 0.027 (4) | 1.2591 (10) | 1.086 (3) | 0.103 (2) | 0.258 (6) |
H20C | −0.0605 | 1.2561 | 1.0439 | 0.124* | 0.258 (6) |
H20D | 0.0210 | 1.2562 | 1.1463 | 0.124* | 0.258 (6) |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0819 (9) | 0.0691 (9) | 0.0610 (8) | −0.0156 (7) | 0.0268 (7) | −0.0184 (6) |
O2 | 0.1453 (15) | 0.0707 (10) | 0.0661 (9) | 0.0110 (9) | 0.0526 (10) | −0.0165 (7) |
O3 | 0.1471 (15) | 0.0615 (9) | 0.0743 (10) | 0.0397 (9) | 0.0445 (10) | −0.0029 (8) |
N1 | 0.0877 (11) | 0.0440 (8) | 0.0398 (8) | 0.0137 (7) | 0.0233 (7) | 0.0026 (6) |
N2 | 0.0624 (9) | 0.0405 (7) | 0.0401 (7) | 0.0093 (6) | 0.0158 (6) | 0.0030 (6) |
C1 | 0.0582 (10) | 0.0426 (9) | 0.0392 (9) | 0.0031 (8) | 0.0140 (7) | −0.0008 (7) |
C2 | 0.0558 (10) | 0.0399 (9) | 0.0390 (9) | 0.0005 (7) | 0.0158 (7) | 0.0000 (7) |
C3 | 0.0745 (12) | 0.0514 (10) | 0.0420 (9) | 0.0053 (9) | 0.0212 (8) | 0.0077 (8) |
C4 | 0.0724 (12) | 0.0558 (11) | 0.0394 (9) | −0.0028 (9) | 0.0243 (8) | −0.0021 (8) |
C5 | 0.0639 (11) | 0.0422 (9) | 0.0473 (10) | −0.0050 (8) | 0.0233 (8) | −0.0073 (7) |
C6 | 0.0795 (12) | 0.0391 (9) | 0.0451 (10) | 0.0076 (8) | 0.0207 (9) | 0.0020 (7) |
C7 | 0.0662 (11) | 0.0398 (9) | 0.0377 (9) | 0.0034 (8) | 0.0179 (8) | −0.0004 (7) |
C8 | 0.0630 (11) | 0.0465 (10) | 0.0396 (9) | 0.0106 (8) | 0.0146 (8) | −0.0004 (7) |
C9 | 0.0673 (12) | 0.0607 (12) | 0.0557 (11) | 0.0019 (9) | 0.0206 (9) | −0.0064 (9) |
C10 | 0.0667 (12) | 0.0876 (15) | 0.0654 (12) | 0.0048 (11) | 0.0291 (10) | −0.0104 (11) |
C11 | 0.0724 (13) | 0.0841 (15) | 0.0542 (11) | 0.0195 (11) | 0.0224 (10) | −0.0142 (10) |
C12 | 0.0739 (13) | 0.0579 (11) | 0.0455 (10) | 0.0130 (10) | 0.0093 (9) | −0.0108 (8) |
C13 | 0.0608 (11) | 0.0507 (10) | 0.0417 (9) | 0.0078 (8) | 0.0118 (8) | −0.0020 (8) |
C14 | 0.0747 (14) | 0.0818 (15) | 0.0828 (15) | −0.0122 (12) | 0.0129 (11) | −0.0203 (12) |
C15 | 0.0793 (13) | 0.0460 (10) | 0.0529 (11) | 0.0168 (9) | 0.0158 (9) | 0.0044 (8) |
C16 | 0.1111 (18) | 0.0497 (11) | 0.0806 (14) | 0.0041 (11) | 0.0386 (13) | 0.0131 (10) |
C17 | 0.0878 (15) | 0.0715 (14) | 0.0733 (14) | 0.0173 (11) | 0.0039 (11) | 0.0000 (11) |
C18 | 0.0757 (16) | 0.101 (2) | 0.111 (2) | −0.0132 (13) | 0.0018 (13) | −0.0121 (15) |
C19 | 0.0810 (13) | 0.0475 (10) | 0.0584 (12) | −0.0050 (9) | 0.0315 (10) | −0.0091 (9) |
C20 | 0.153 (6) | 0.058 (2) | 0.108 (4) | 0.034 (3) | 0.053 (5) | −0.011 (2) |
C21 | 0.117 (4) | 0.081 (2) | 0.142 (4) | 0.041 (3) | 0.031 (3) | 0.006 (3) |
C21A | 0.117 (4) | 0.081 (2) | 0.142 (4) | 0.041 (3) | 0.031 (3) | 0.006 (3) |
C20A | 0.153 (6) | 0.058 (2) | 0.108 (4) | 0.034 (3) | 0.053 (5) | −0.011 (2) |
O1—C13 | 1.365 (2) | C12—C13 | 1.388 (2) |
O1—C14 | 1.422 (2) | C12—H12 | 0.9300 |
O2—C19 | 1.198 (2) | C14—H14A | 0.9600 |
O3—C19 | 1.324 (2) | C14—H14B | 0.9600 |
O3—C20A | 1.456 (5) | C14—H14C | 0.9600 |
O3—C20 | 1.456 (4) | C15—C17 | 1.501 (3) |
N1—C1 | 1.306 (2) | C15—C16 | 1.546 (3) |
N1—C7 | 1.390 (2) | C15—H15 | 0.9800 |
N2—C1 | 1.376 (2) | C16—H16A | 0.9600 |
N2—C2 | 1.385 (2) | C16—H16B | 0.9600 |
N2—C15 | 1.480 (2) | C16—H16C | 0.9600 |
C1—C8 | 1.485 (2) | C17—C18 | 1.489 (3) |
C2—C3 | 1.392 (2) | C17—H17A | 0.9700 |
C2—C7 | 1.397 (2) | C17—H17B | 0.9700 |
C3—C4 | 1.372 (2) | C18—H18A | 0.9600 |
C3—H3 | 0.9300 | C18—H18B | 0.9600 |
C4—C5 | 1.398 (2) | C18—H18C | 0.9600 |
C4—H4 | 0.9300 | C20—C21 | 1.441 (12) |
C5—C6 | 1.384 (2) | C20—H20A | 0.9700 |
C5—C19 | 1.480 (2) | C20—H20B | 0.9700 |
C6—C7 | 1.387 (2) | C21—H21A | 0.9600 |
C6—H6 | 0.9300 | C21—H21B | 0.9600 |
C8—C9 | 1.381 (3) | C21—H21C | 0.9600 |
C8—C13 | 1.392 (2) | C21A—C20A | 1.440 (13) |
C9—C10 | 1.381 (3) | C21A—H21D | 0.9600 |
C9—H9 | 0.9300 | C21A—H21E | 0.9600 |
C10—C11 | 1.370 (3) | C21A—H21F | 0.9600 |
C10—H10 | 0.9300 | C20A—H20C | 0.9700 |
C11—C12 | 1.373 (3) | C20A—H20D | 0.9700 |
C11—H11 | 0.9300 | ||
C13—O1—C14 | 118.20 (15) | N2—C15—C17 | 111.19 (16) |
C19—O3—C20A | 118.4 (17) | N2—C15—C16 | 111.76 (15) |
C19—O3—C20 | 116.7 (6) | C17—C15—C16 | 113.08 (17) |
C1—N1—C7 | 104.53 (13) | N2—C15—H15 | 106.8 |
C1—N2—C2 | 106.11 (12) | C17—C15—H15 | 106.8 |
C1—N2—C15 | 125.83 (13) | C16—C15—H15 | 106.8 |
C2—N2—C15 | 127.75 (13) | C15—C16—H16A | 109.5 |
N1—C1—N2 | 113.72 (13) | C15—C16—H16B | 109.5 |
N1—C1—C8 | 122.94 (14) | H16A—C16—H16B | 109.5 |
N2—C1—C8 | 123.27 (14) | C15—C16—H16C | 109.5 |
N2—C2—C3 | 133.33 (15) | H16A—C16—H16C | 109.5 |
N2—C2—C7 | 105.16 (13) | H16B—C16—H16C | 109.5 |
C3—C2—C7 | 121.52 (15) | C18—C17—C15 | 113.38 (19) |
C4—C3—C2 | 117.02 (15) | C18—C17—H17A | 108.9 |
C4—C3—H3 | 121.5 | C15—C17—H17A | 108.9 |
C2—C3—H3 | 121.5 | C18—C17—H17B | 108.9 |
C3—C4—C5 | 122.30 (15) | C15—C17—H17B | 108.9 |
C3—C4—H4 | 118.8 | H17A—C17—H17B | 107.7 |
C5—C4—H4 | 118.8 | C17—C18—H18A | 109.5 |
C6—C5—C4 | 120.35 (15) | C17—C18—H18B | 109.5 |
C6—C5—C19 | 121.18 (16) | H18A—C18—H18B | 109.5 |
C4—C5—C19 | 118.47 (15) | C17—C18—H18C | 109.5 |
C5—C6—C7 | 118.24 (15) | H18A—C18—H18C | 109.5 |
C5—C6—H6 | 120.9 | H18B—C18—H18C | 109.5 |
C7—C6—H6 | 120.9 | O2—C19—O3 | 122.81 (18) |
C6—C7—N1 | 128.98 (15) | O2—C19—C5 | 124.93 (19) |
C6—C7—C2 | 120.55 (14) | O3—C19—C5 | 112.26 (15) |
N1—C7—C2 | 110.46 (14) | C21—C20—O3 | 106.8 (8) |
C9—C8—C13 | 119.04 (15) | C21—C20—H20A | 110.4 |
C9—C8—C1 | 119.08 (16) | O3—C20—H20A | 110.4 |
C13—C8—C1 | 121.81 (16) | C21—C20—H20B | 110.4 |
C10—C9—C8 | 120.85 (19) | O3—C20—H20B | 110.4 |
C10—C9—H9 | 119.6 | H20A—C20—H20B | 108.6 |
C8—C9—H9 | 119.6 | C20—C21—H21A | 109.5 |
C11—C10—C9 | 119.33 (19) | C20—C21—H21B | 109.5 |
C11—C10—H10 | 120.3 | H21A—C21—H21B | 109.5 |
C9—C10—H10 | 120.3 | C20—C21—H21C | 109.5 |
C10—C11—C12 | 121.27 (17) | H21A—C21—H21C | 109.5 |
C10—C11—H11 | 119.4 | H21B—C21—H21C | 109.5 |
C12—C11—H11 | 119.4 | C20A—C21A—H21D | 109.5 |
C11—C12—C13 | 119.38 (18) | C20A—C21A—H21E | 109.5 |
C11—C12—H12 | 120.3 | H21D—C21A—H21E | 109.5 |
C13—C12—H12 | 120.3 | C20A—C21A—H21F | 109.5 |
O1—C13—C12 | 124.40 (17) | H21D—C21A—H21F | 109.5 |
O1—C13—C8 | 115.49 (14) | H21E—C21A—H21F | 109.5 |
C12—C13—C8 | 120.11 (17) | C21A—C20A—O3 | 101.4 (11) |
O1—C14—H14A | 109.5 | C21A—C20A—H20C | 111.5 |
O1—C14—H14B | 109.5 | O3—C20A—H20C | 111.5 |
H14A—C14—H14B | 109.5 | C21A—C20A—H20D | 111.5 |
O1—C14—H14C | 109.5 | O3—C20A—H20D | 111.5 |
H14A—C14—H14C | 109.5 | H20C—C20A—H20D | 109.3 |
H14B—C14—H14C | 109.5 | ||
C7—N1—C1—N2 | 0.4 (2) | C1—C8—C9—C10 | −178.21 (17) |
C7—N1—C1—C8 | −176.62 (16) | C8—C9—C10—C11 | 0.0 (3) |
C2—N2—C1—N1 | −1.2 (2) | C9—C10—C11—C12 | 0.8 (3) |
C15—N2—C1—N1 | −175.22 (16) | C10—C11—C12—C13 | −0.5 (3) |
C2—N2—C1—C8 | 175.86 (16) | C14—O1—C13—C12 | −10.5 (3) |
C15—N2—C1—C8 | 1.8 (3) | C14—O1—C13—C8 | 169.60 (17) |
C1—N2—C2—C3 | −178.75 (18) | C11—C12—C13—O1 | 179.54 (17) |
C15—N2—C2—C3 | −4.9 (3) | C11—C12—C13—C8 | −0.6 (3) |
C1—N2—C2—C7 | 1.37 (18) | C9—C8—C13—O1 | −178.76 (16) |
C15—N2—C2—C7 | 175.26 (16) | C1—C8—C13—O1 | −1.7 (2) |
N2—C2—C3—C4 | 180.00 (18) | C9—C8—C13—C12 | 1.3 (3) |
C7—C2—C3—C4 | −0.1 (3) | C1—C8—C13—C12 | 178.40 (16) |
C2—C3—C4—C5 | 1.5 (3) | C1—N2—C15—C17 | 111.1 (2) |
C3—C4—C5—C6 | −1.5 (3) | C2—N2—C15—C17 | −61.7 (2) |
C3—C4—C5—C19 | 177.90 (17) | C1—N2—C15—C16 | −121.50 (19) |
C4—C5—C6—C7 | 0.2 (3) | C2—N2—C15—C16 | 65.7 (2) |
C19—C5—C6—C7 | −179.26 (17) | N2—C15—C17—C18 | −55.0 (2) |
C5—C6—C7—N1 | −178.97 (17) | C16—C15—C17—C18 | 178.28 (19) |
C5—C6—C7—C2 | 1.2 (3) | C20A—O3—C19—O2 | −13.3 (18) |
C1—N1—C7—C6 | −179.38 (19) | C20—O3—C19—O2 | 1.3 (5) |
C1—N1—C7—C2 | 0.5 (2) | C20A—O3—C19—C5 | 167.2 (17) |
N2—C2—C7—C6 | 178.70 (16) | C20—O3—C19—C5 | −178.2 (5) |
C3—C2—C7—C6 | −1.2 (3) | C6—C5—C19—O2 | −172.8 (2) |
N2—C2—C7—N1 | −1.19 (19) | C4—C5—C19—O2 | 7.8 (3) |
C3—C2—C7—N1 | 178.91 (16) | C6—C5—C19—O3 | 6.7 (3) |
N1—C1—C8—C9 | 65.8 (2) | C4—C5—C19—O3 | −172.74 (17) |
N2—C1—C8—C9 | −110.9 (2) | C19—O3—C20—C21 | 172.8 (5) |
N1—C1—C8—C13 | −111.2 (2) | C20A—O3—C20—C21 | −86 (10) |
N2—C1—C8—C13 | 72.0 (2) | C19—O3—C20A—C21A | 119 (2) |
C13—C8—C9—C10 | −1.1 (3) | C20—O3—C20A—C21A | 33 (6) |
Cg is the centroid of the N1/N2/C1/C2/C7 ring. |
D—H···A | D—H | H···A | D···A | D—H···A |
C12—H12···N1i | 0.93 | 2.56 | 3.471 (2) | 165 |
C20A—H20C···Cgii | 0.97 | 2.90 | 3.71 (4) | 141 |
Symmetry codes: (i) −x+1/2, y−1/2, −z+3/2; (ii) −x, −y+2, −z+2. |
Experimental details
Crystal data | |
Chemical formula | C21H24N2O3 |
Mr | 352.42 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 296 |
a, b, c (Å) | 10.6746 (3), 12.3344 (4), 15.6158 (5) |
β (°) | 106.901 (1) |
V (Å3) | 1967.25 (11) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.52 × 0.44 × 0.32 |
Data collection | |
Diffractometer | Bruker SMART APEXII CCD area-detector |
Absorption correction | Multi-scan (SADABS; Bruker, 2009) |
Tmin, Tmax | 0.959, 0.975 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 17688, 3475, 2712 |
Rint | 0.025 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.045, 0.122, 1.05 |
No. of reflections | 3475 |
No. of parameters | 245 |
No. of restraints | 3 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.35, −0.18 |
Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).
Cg is the centroid of the N1/N2/C1/C2/C7 ring. |
D—H···A | D—H | H···A | D···A | D—H···A |
C12—H12···N1i | 0.93 | 2.56 | 3.471 (2) | 165 |
C20A—H20C···Cgii | 0.97 | 2.90 | 3.71 (4) | 141 |
Symmetry codes: (i) −x+1/2, y−1/2, −z+3/2; (ii) −x, −y+2, −z+2. |
Acknowledgements
NA, HO and ASAR acknowledge the Ministry of Science, Technology and Innovations of Malaysia for funding the synthetic chemistry work under 304/PFARMASI/650544. NA thanks Universiti Sains Malaysia for the award of a postdoctoral fellowship.
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Microwave-assisted synthesis of heterocycles proves to be an invaluable technology in the fields of medicinal chemistry and drug discovery (Kappe & Dallinger, 2006). The utility of high-speed microwave chemistry is evident from the reported synthesis of privileged structures (Evans et al., 1988; Nicolaou et al., 2000) such as benzodiazepine (Santagada et al., 2001), indoles (Loupy, 2002) and benzimidazoles (Wang et al., 2011; VanVliet et al., 2005). As a part of our on-going work in benzimidazole synthesis under microwave conditions (Hamzah et al., 2011), we present herein the X-ray crystal structure of the title compound.
The molecular structure of the title compound (Fig. 1) is similiar to the previously reported ethyl 1-sec-butyl-2-(4-methoxyphenyl) -1H-benzimidazole-5-carboxylate (Arumugam et al., 2010) in that only the position of the methoxy group is different. The benzene [C8—C13] ring and benzimidazole ring system [N1/N2/C1-C7] are essentially planar with maximum deviation of 0.050 (1)Å for atom N2. The mean-planes of the rings form a dihedral angle of 69.94 (7)°. The bond lengths (Allen et al., 1987) and angles aree in the normal ranges and comparable to those in para-methoxy derivative. The ethyl atoms (C20 & C21) of ethanoate fragment are disordered over two positions with refined site occupancies of 0.742 (6) and 0.258 (6). In the crystal, a C12—H12···N1i hydrogen bond connects molecules to form a zigzag chain propagating along the b axis (Fig. 2). An weak intermolecular C20A—H20C···Cgii (minor component of disorder) interaction is also observed; Cg1 is the centroid of N1/N2/C1/C2/C7.