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Acta Crystallogr Sect E Struct Rep Online. Oct 1, 2012; 68(Pt 10): o3032.
Published online Sep 29, 2012. doi:  10.1107/S1600536812040299
PMCID: PMC3470386
Ethyl 2,4-dimethyl­pyrido[1,2-a]benz­imidazole-3-carboxyl­ate
Ai Guo Zhu,a Zhuo Ming Ma,a Lin Jie Li,a Tian Tian Wei,a and Yan Qing Gea*
aSchool of Chemistry and Chemical Engineering, Taishan Medical University, Tai an 271016, People’s Republic of China
Correspondence e-mail: yqge/at/yahoo.cn
Received September 12, 2012; Accepted September 23, 2012.
Abstract
The title compound, C16H16N2O2, was synthesized using a novel tandem annulation reaction between 1-(1H-benzo[d]imidazol-2-yl)ethanone and ethyl (E)-4-bromo­but-2-enoate under mild conditions. The dihedral angles formed by the mean plane of the five-membered imidazole ring with the dihydro­pyridin and benzene rings are 1.54 (9) and 1.85 (9)°, respectively.
Related literature  
For the synthesis and characterization of pyrido[1,2-a]benz­imidazole derivatives, see: Ge et al. (2009 [triangle], 2011 [triangle]). For pharmaceutical applications of nitro­gen-containing heterocyclic compounds, see: Badawey & Kappe (1999 [triangle]).
An external file that holds a picture, illustration, etc.
Object name is e-68-o3032-scheme1.jpg Object name is e-68-o3032-scheme1.jpg
Crystal data  
  • C16H16N2O2
  • M r = 268.31
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-68-o3032-efi1.jpg
  • a = 7.671 (4) Å
  • b = 13.174 (7) Å
  • c = 13.807 (7) Å
  • β = 102.680 (7)°
  • V = 1361.3 (12) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.09 mm−1
  • T = 273 K
  • 0.32 × 0.28 × 0.26 mm
Data collection  
  • Bruker SMART APEXII CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2005 [triangle]) T min = 0.973, T max = 0.978
  • 6894 measured reflections
  • 2389 independent reflections
  • 2056 reflections with I > 2σ(I)
  • R int = 0.086
Refinement  
  • R[F 2 > 2σ(F 2)] = 0.047
  • wR(F 2) = 0.134
  • S = 1.05
  • 2389 reflections
  • 184 parameters
  • H-atom parameters constrained
  • Δρmax = 0.23 e Å−3
  • Δρmin = −0.26 e Å−3
Data collection: APEX2 (Bruker, 2005 [triangle]); cell refinement: SAINT (Bruker, 2005 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: SHELXTL (Sheldrick, 2008 [triangle]); software used to prepare material for publication: SHELXTL.
Supplementary Material
Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812040299/rz5006sup1.cif
Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812040299/rz5006Isup2.hkl
Supplementary material file. DOI: 10.1107/S1600536812040299/rz5006Isup3.cml
Additional supplementary materials: crystallographic information; 3D view; checkCIF report
Acknowledgments
This study was supported by the Natural Science Foundation of Shandong Province (No. ZR2012BL04).
supplementary crystallographic information
Comment
The synthesis of nitrogen-containing heterocyclic compounds has been a subject of great interest due to the wide application in pharmaceutical fields (Ge et al., 2009; Ge et al., 2011). Some pyrido[1,2-a]benzimidazole derivatives have been of interest for their biological activities, such as antineoplastic activity and central GABA-A receptor modulators for the treatment of anxiety (Badawey et al.; 1999).
The fused-ring system of the title compound (Fig. 1) is approximately planar, the dihedral angles formed by the mean planes through the imidazole ring with the dihydropyridine and benzene rings being 1.54 (9) and 1.85 (9)°, respectively. The mean plane defined by the carboxylate group (C3/C4/O1/O2) is tilted by 60.38 (5)° with respect to the plane of the benzene ring. The crystal structure is stabilized only by van der Waals interactions.
Experimental
To a 50 ml round-bottomed flask were added 1-(1H-benzo[d]imidazol-2-yl)ethanone (1.00 mmol), (E)-ethyl 4-bromobut-2-enoate (2.00 mmol), potassium carbonate (0.28 g, 2.05 mmol) and dry DMF (10 ml). The mixture was stirred at room temperature for 6 h. The solvent was removed under reduced pressure and the product was isolated by column chromatography on silica gel (yield 70%). Crystals of the title compound suitable for X-ray diffraction were obtained by allowing a refluxed solution of the product in ethyl acetate to cool slowly to room temperature (without temperature control) and allowing the solvent to slowly evaporate for 2 d.
Refinement
All H atoms were placed in geometrically calculated positions and refined using a riding model, with C—H = 0.93-0.97 Å and with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(C) for methyl H atoms. A rotating group model was applied to the methyl groups.
Figures
Fig. 1.
Fig. 1.
The molecular structure of the title compound, showing displacement ellipsoids drawn at the 50% probability level.
Crystal data
C16H16N2O2F(000) = 568
Mr = 268.31Dx = 1.309 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 4261 reflections
a = 7.671 (4) Åθ = 3.0–28.2°
b = 13.174 (7) ŵ = 0.09 mm1
c = 13.807 (7) ÅT = 273 K
β = 102.680 (7)°Block, colourless
V = 1361.3 (12) Å30.32 × 0.28 × 0.26 mm
Z = 4
Data collection
Bruker SMART APEXII CCD area-detector diffractometer2389 independent reflections
Radiation source: fine-focus sealed tube2056 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.086
phi and ω scansθmax = 25.0°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Bruker, 2005)h = −5→9
Tmin = 0.973, Tmax = 0.978k = −15→14
6894 measured reflectionsl = −16→16
Refinement
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.047Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.134H-atom parameters constrained
S = 1.05w = 1/[σ2(Fo2) + (0.075P)2 + 0.2415P] where P = (Fo2 + 2Fc2)/3
2389 reflections(Δ/σ)max = 0.052
184 parametersΔρmax = 0.23 e Å3
0 restraintsΔρmin = −0.26 e Å3
Special details
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.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)
xyzUiso*/Ueq
N10.75792 (18)−0.01609 (10)0.27023 (9)0.0440 (4)
N20.72152 (15)−0.05514 (9)0.10717 (9)0.0351 (3)
O11.03253 (17)0.23943 (10)−0.01104 (10)0.0594 (4)
O20.80757 (16)0.30461 (8)0.04828 (9)0.0487 (3)
C10.7586 (4)0.47805 (16)0.07813 (19)0.0802 (7)
H1A0.63350.46810.05050.120*
H1B0.79070.54670.06640.120*
H1C0.78300.46540.14830.120*
C20.8641 (3)0.40713 (12)0.03063 (14)0.0531 (5)
H2A0.84290.4204−0.04010.064*
H2B0.99060.41550.05900.064*
C30.9069 (2)0.22855 (11)0.02743 (11)0.0400 (4)
C40.84263 (19)0.12847 (11)0.05743 (10)0.0365 (4)
C50.78468 (19)0.05213 (11)−0.01807 (10)0.0360 (4)
C60.72718 (19)−0.03754 (12)0.00956 (10)0.0373 (4)
H60.6910−0.0881−0.03760.045*
C70.77753 (19)0.01635 (11)0.18186 (10)0.0358 (3)
C80.84377 (19)0.11132 (11)0.15597 (11)0.0376 (4)
C90.9153 (2)0.18433 (13)0.23890 (12)0.0505 (4)
H9A1.00140.22840.21960.076*
H9B0.97140.14710.29720.076*
H9C0.81890.22410.25290.076*
C100.7900 (2)0.07044 (13)−0.12539 (11)0.0460 (4)
H10A0.74270.0123−0.16430.069*
H10B0.91130.0816−0.13060.069*
H10C0.71940.1291−0.14950.069*
C110.66408 (19)−0.13957 (11)0.15187 (11)0.0377 (4)
C120.6866 (2)−0.11231 (12)0.25233 (11)0.0410 (4)
C130.6335 (2)−0.18090 (14)0.31784 (13)0.0527 (5)
H130.6463−0.16520.38470.063*
C140.5616 (2)−0.27222 (14)0.28027 (14)0.0566 (5)
H140.5252−0.31830.32290.068*
C150.5415 (2)−0.29809 (13)0.17999 (14)0.0551 (5)
H150.4928−0.36070.15770.066*
C160.5929 (2)−0.23193 (12)0.11366 (13)0.0473 (4)
H160.5805−0.24840.04700.057*
Atomic displacement parameters (Å2)
U11U22U33U12U13U23
N10.0471 (8)0.0517 (8)0.0327 (7)−0.0038 (6)0.0078 (5)0.0015 (6)
N20.0331 (6)0.0393 (7)0.0329 (6)0.0012 (5)0.0070 (5)−0.0004 (5)
O10.0582 (8)0.0569 (7)0.0723 (9)−0.0017 (6)0.0340 (7)0.0058 (6)
O20.0493 (7)0.0397 (6)0.0601 (7)0.0010 (5)0.0186 (5)0.0031 (5)
C10.0948 (17)0.0504 (11)0.1022 (18)0.0057 (11)0.0363 (14)−0.0058 (11)
C20.0638 (11)0.0409 (9)0.0546 (10)−0.0031 (8)0.0126 (8)0.0046 (8)
C30.0396 (8)0.0440 (9)0.0363 (8)0.0011 (7)0.0080 (6)0.0016 (6)
C40.0319 (7)0.0413 (8)0.0366 (8)0.0036 (6)0.0085 (6)0.0005 (6)
C50.0321 (7)0.0438 (8)0.0324 (7)0.0057 (6)0.0074 (6)0.0000 (6)
C60.0366 (8)0.0432 (8)0.0314 (7)0.0027 (6)0.0055 (6)−0.0043 (6)
C70.0333 (7)0.0421 (8)0.0318 (7)0.0019 (6)0.0064 (6)−0.0017 (6)
C80.0355 (8)0.0409 (8)0.0360 (8)0.0017 (6)0.0069 (6)−0.0024 (6)
C90.0584 (10)0.0523 (10)0.0397 (9)−0.0096 (8)0.0084 (7)−0.0069 (7)
C100.0473 (9)0.0566 (10)0.0345 (8)0.0042 (7)0.0097 (7)0.0030 (7)
C110.0311 (7)0.0401 (8)0.0419 (8)0.0032 (6)0.0081 (6)0.0046 (6)
C120.0352 (8)0.0488 (9)0.0380 (8)0.0030 (6)0.0057 (6)0.0067 (6)
C130.0480 (10)0.0654 (11)0.0432 (9)−0.0023 (8)0.0067 (7)0.0143 (8)
C140.0476 (10)0.0582 (11)0.0622 (11)−0.0028 (8)0.0085 (8)0.0237 (9)
C150.0480 (10)0.0450 (9)0.0711 (12)−0.0029 (7)0.0105 (8)0.0066 (8)
C160.0449 (9)0.0444 (9)0.0534 (10)−0.0003 (7)0.0124 (7)−0.0015 (7)
Geometric parameters (Å, º)
N1—C71.332 (2)C6—H60.9300
N1—C121.381 (2)C7—C81.425 (2)
N2—C61.3775 (19)C8—C91.504 (2)
N2—C111.3899 (19)C9—H9A0.9600
N2—C71.393 (2)C9—H9B0.9600
O1—C31.2065 (19)C9—H9C0.9600
O2—C31.3283 (19)C10—H10A0.9600
O2—C21.455 (2)C10—H10B0.9600
C1—C21.480 (3)C10—H10C0.9600
C1—H1A0.9600C11—C161.389 (2)
C1—H1B0.9600C11—C121.406 (2)
C1—H1C0.9600C12—C131.401 (2)
C2—H2A0.9700C13—C141.377 (3)
C2—H2B0.9700C13—H130.9300
C3—C41.498 (2)C14—C151.401 (3)
C4—C81.377 (2)C14—H140.9300
C4—C51.446 (2)C15—C161.383 (2)
C5—C61.345 (2)C15—H150.9300
C5—C101.511 (2)C16—H160.9300
C7—N1—C12104.51 (12)C4—C8—C9124.71 (14)
C6—N2—C11130.57 (13)C7—C8—C9117.46 (13)
C6—N2—C7122.66 (13)C8—C9—H9A109.5
C11—N2—C7106.78 (12)C8—C9—H9B109.5
C3—O2—C2117.24 (13)H9A—C9—H9B109.5
C2—C1—H1A109.5C8—C9—H9C109.5
C2—C1—H1B109.5H9A—C9—H9C109.5
H1A—C1—H1B109.5H9B—C9—H9C109.5
C2—C1—H1C109.5C5—C10—H10A109.5
H1A—C1—H1C109.5C5—C10—H10B109.5
H1B—C1—H1C109.5H10A—C10—H10B109.5
O2—C2—C1107.44 (15)C5—C10—H10C109.5
O2—C2—H2A110.2H10A—C10—H10C109.5
C1—C2—H2A110.2H10B—C10—H10C109.5
O2—C2—H2B110.2C16—C11—N2131.97 (15)
C1—C2—H2B110.2C16—C11—C12123.44 (14)
H2A—C2—H2B108.5N2—C11—C12104.56 (13)
O1—C3—O2123.88 (14)N1—C12—C13129.53 (15)
O1—C3—C4124.72 (14)N1—C12—C11111.65 (13)
O2—C3—C4111.39 (13)C13—C12—C11118.81 (15)
C8—C4—C5122.15 (14)C14—C13—C12118.01 (17)
C8—C4—C3119.11 (13)C14—C13—H13121.0
C5—C4—C3118.72 (13)C12—C13—H13121.0
C6—C5—C4118.31 (14)C13—C14—C15122.22 (16)
C6—C5—C10119.97 (14)C13—C14—H14118.9
C4—C5—C10121.71 (14)C15—C14—H14118.9
C5—C6—N2120.53 (13)C16—C15—C14121.04 (17)
C5—C6—H6119.7C16—C15—H15119.5
N2—C6—H6119.7C14—C15—H15119.5
N1—C7—N2112.50 (13)C15—C16—C11116.48 (16)
N1—C7—C8129.02 (14)C15—C16—H16121.8
N2—C7—C8118.48 (13)C11—C16—H16121.8
C4—C8—C7117.80 (13)
Footnotes
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: RZ5006).
References
  • Badawey, E. S. A. M. & Kappe, T. (1999). Eur. J. Med. Chem. 34, 663–667. [PubMed]
  • Bruker (2005). APEX2, SAINT and SADABS Bruker AXS Inc., Madison, Wisconsin, USA.
  • Ge, Y. Q., Jia, J., Li, Y., Yin, L. & Wang, J. W. (2009). Heterocycles, 78, 197–206.
  • Ge, Y. Q., Jia, J., Yang, H., Tao, X. T. & Wang, J. W. (2011). Dyes Pigm. 88, 344–349.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
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