organic compounds
3-(4-Fluorophenyl)-6-methoxy-2-(4-pyridyl)quinoxaline
aInstitute of Pharmacy, Department of Pharmaceutical and Medicinal Chemistry, Eberhard-Karls-University Tübingen, Auf der Morgenstelle 8, 72076 Tübingen, Germany, and bDepartment of Organic Chemistry, Johannes Gutenberg-University Mainz, Duesbergweg 10-14, D-55099 Mainz, Germany
*Correspondence e-mail: stefan.laufer@uni-tuebingen.de
In the title compound, C20H14FN3O, the quinoxaline system makes dihedral angles of 32.38 (7) and 48.04 (7)° with the 4-fluorophenyl and pyridine rings, respectively. The 4-fluorophenyl ring makes a dihedral angle of 57.77 (9)° with the pyridine ring. In the crystal, the molecules form dimeric C—H⋯N hydrogen-bonded R22(20) ring motifs lying about crystallographic inversion centers. The dimeric units stack via π–π interactions between methoxyphenyl rings and pyridine–fluorophenyl rings with centroid–centroid distances of 3.720 (1) and 3.823 (1) Å, respectively. The respective average perpendicular distances are 3.421 and 3.378 Å, with dihedral angles between the rings of 1.31 (9) and 11.64 (9)°.
Related literature
Many chinoxaline derivatives have been prepared and their biological activity have been studied, see: He et al. (2003); Kim et al. (2004). For intermolecular C—H⋯N hydrogen bonds, see: Taylor & Kennard (1982). For distinct ring motifs formed via O—H⋯N hydrogen bonds, see: Habib & Janiak (2008); Friščič & MacGillivray (2003). For graph-set notation, see: Bernstein et al. (1995).
Experimental
Crystal data
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Data collection
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Refinement
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Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell CAD-4 Software; data reduction: CORINC (Dräger & Gattow, 1971); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: PLATON.
Supporting information
10.1107/S1600536809022119/si2176sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536809022119/si2176Isup2.hkl
The title compound I was prepared by irradiating 1-(4-fluorophenyl)-2-(pyridin-4-yl)ethane-1,2-dion (137 mg, 0.6 mmol), o-phenylendiamine (82 mg, 0.6 mmol) and methanol-acetic acid (9:1, 6 ml) in a sealed tube at 433 K for 5 min by moderating the initial microwave power (250 W). After the mixture was cooled to room temperature in a stream of compressed air, the solvent was removed under reduced pressure and the residue was purified by flash
(silica gel, from petroleum ether/ ethyl acetate 2:1 to 1:2) to yield 82 mg of I. Crystals suitable for X-ray analysis were obtained by slow crystallization from diethylether/n-hexane.Hydrogen atoms attached to carbons were placed at calculated positions with C—H = 0.95 Å (aromatic) or 0.98–0.99 Å (sp3 C-atom). All H atoms were refined in the riding-model approximation with isotropic displacement parameters (set at 1.2–1.5 times of the Ueq of the parent atom). The structure was solved using a preliminary data collection set. The final measurement on CAD4-diffractometer covered only 1/8 (unique reflection) of the reflection sphere, thus Rint = 0.0000.
Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell
CAD-4 Software (Enraf–Nonius, 1989); data reduction: CORINC (Dräger & Gattow, 1971); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: PLATON (Spek, 2009).C20H14FN3O | F(000) = 1376 |
Mr = 331.34 | Dx = 1.412 Mg m−3 |
Orthorhombic, Pbca | Cu Kα radiation, λ = 1.54178 Å |
Hall symbol: -P 2ac 2ab | Cell parameters from 25 reflections |
a = 7.3886 (4) Å | θ = 61–69° |
b = 12.2071 (8) Å | µ = 0.80 mm−1 |
c = 34.562 (6) Å | T = 193 K |
V = 3117.3 (6) Å3 | Plate, colourless |
Z = 8 | 0.45 × 0.22 × 0.13 mm |
Enraf–Nonius CAD-4 diffractometer | Rint = 0.000 |
Radiation source: FR571 rotating anode | θmax = 70.1°, θmin = 2.6° |
Graphite monochromator | h = 0→8 |
ω/2θ scans | k = 0→14 |
2950 measured reflections | l = 0→42 |
2950 independent reflections | 3 standard reflections every 60 min |
2542 reflections with I > 2σ(I) | intensity decay: 2% |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.044 | H-atom parameters constrained |
wR(F2) = 0.124 | w = 1/[σ2(Fo2) + (0.063P)2 + 1.8096P] where P = (Fo2 + 2Fc2)/3 |
S = 1.05 | (Δ/σ)max < 0.001 |
2950 reflections | Δρmax = 0.32 e Å−3 |
228 parameters | Δρmin = −0.24 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0024 (2) |
C20H14FN3O | V = 3117.3 (6) Å3 |
Mr = 331.34 | Z = 8 |
Orthorhombic, Pbca | Cu Kα radiation |
a = 7.3886 (4) Å | µ = 0.80 mm−1 |
b = 12.2071 (8) Å | T = 193 K |
c = 34.562 (6) Å | 0.45 × 0.22 × 0.13 mm |
Enraf–Nonius CAD-4 diffractometer | Rint = 0.000 |
2950 measured reflections | 3 standard reflections every 60 min |
2950 independent reflections | intensity decay: 2% |
2542 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.044 | 0 restraints |
wR(F2) = 0.124 | H-atom parameters constrained |
S = 1.05 | Δρmax = 0.32 e Å−3 |
2950 reflections | Δρmin = −0.24 e Å−3 |
228 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 | ||
C1 | 0.0332 (2) | 0.08992 (13) | 0.65003 (5) | 0.0212 (4) | |
C2 | 0.1240 (2) | −0.01069 (13) | 0.64015 (5) | 0.0234 (4) | |
N3 | 0.1695 (2) | −0.08283 (11) | 0.66708 (4) | 0.0248 (3) | |
C4 | 0.1415 (2) | −0.05500 (14) | 0.70477 (5) | 0.0241 (4) | |
C5 | 0.1912 (2) | −0.12816 (15) | 0.73464 (5) | 0.0280 (4) | |
H5 | 0.2383 | −0.1984 | 0.7284 | 0.034* | |
C6 | 0.1717 (3) | −0.09798 (15) | 0.77228 (5) | 0.0290 (4) | |
H6 | 0.2040 | −0.1478 | 0.7922 | 0.035* | |
C7 | 0.1034 (2) | 0.00738 (15) | 0.78208 (5) | 0.0257 (4) | |
C8 | 0.0529 (2) | 0.07962 (14) | 0.75376 (5) | 0.0253 (4) | |
H8 | 0.0074 | 0.1499 | 0.7604 | 0.030* | |
C9 | 0.0691 (2) | 0.04866 (14) | 0.71462 (5) | 0.0224 (4) | |
N10 | 0.01133 (19) | 0.11909 (11) | 0.68664 (4) | 0.0228 (3) | |
C11 | −0.0457 (2) | 0.16507 (13) | 0.62087 (5) | 0.0214 (4) | |
C12 | −0.0501 (2) | 0.27756 (14) | 0.62867 (5) | 0.0240 (4) | |
H12 | 0.0020 | 0.3047 | 0.6519 | 0.029* | |
C13 | −0.1297 (3) | 0.34958 (14) | 0.60292 (5) | 0.0277 (4) | |
H13 | −0.1341 | 0.4258 | 0.6084 | 0.033* | |
C14 | −0.2026 (2) | 0.30841 (15) | 0.56913 (5) | 0.0277 (4) | |
C15 | −0.2047 (3) | 0.19825 (15) | 0.56049 (5) | 0.0286 (4) | |
H15 | −0.2590 | 0.1720 | 0.5374 | 0.034* | |
C16 | −0.1249 (2) | 0.12698 (14) | 0.58669 (5) | 0.0258 (4) | |
H16 | −0.1240 | 0.0507 | 0.5813 | 0.031* | |
F17 | −0.27461 (17) | 0.37943 (9) | 0.54317 (3) | 0.0401 (3) | |
C18 | 0.1841 (2) | −0.03833 (14) | 0.60030 (5) | 0.0239 (4) | |
C19 | 0.1592 (3) | −0.14261 (14) | 0.58520 (5) | 0.0286 (4) | |
H19 | 0.0981 | −0.1973 | 0.5998 | 0.034* | |
C20 | 0.2249 (3) | −0.16553 (15) | 0.54863 (5) | 0.0340 (4) | |
H20 | 0.2038 | −0.2367 | 0.5385 | 0.041* | |
N21 | 0.3161 (2) | −0.09438 (13) | 0.52658 (5) | 0.0344 (4) | |
C22 | 0.3408 (3) | 0.00561 (15) | 0.54154 (5) | 0.0317 (4) | |
H22 | 0.4053 | 0.0580 | 0.5266 | 0.038* | |
C23 | 0.2776 (2) | 0.03680 (14) | 0.57757 (5) | 0.0272 (4) | |
H23 | 0.2979 | 0.1091 | 0.5867 | 0.033* | |
O24 | 0.09436 (18) | 0.02718 (11) | 0.82084 (3) | 0.0324 (3) | |
C25 | 0.0370 (3) | 0.13400 (17) | 0.83218 (6) | 0.0356 (5) | |
H25A | 0.1183 | 0.1888 | 0.8209 | 0.053* | |
H25B | 0.0400 | 0.1398 | 0.8605 | 0.053* | |
H25C | −0.0866 | 0.1468 | 0.8230 | 0.053* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0199 (8) | 0.0226 (8) | 0.0211 (8) | −0.0022 (6) | 0.0009 (6) | −0.0003 (6) |
C2 | 0.0229 (8) | 0.0223 (8) | 0.0248 (8) | −0.0015 (7) | 0.0009 (7) | 0.0012 (6) |
N3 | 0.0253 (7) | 0.0243 (7) | 0.0249 (7) | 0.0000 (6) | 0.0026 (6) | 0.0024 (6) |
C4 | 0.0201 (8) | 0.0264 (8) | 0.0259 (8) | −0.0007 (7) | 0.0018 (6) | 0.0031 (7) |
C5 | 0.0270 (9) | 0.0260 (8) | 0.0311 (9) | 0.0018 (7) | 0.0026 (7) | 0.0058 (7) |
C6 | 0.0267 (9) | 0.0313 (9) | 0.0289 (9) | 0.0013 (8) | −0.0004 (7) | 0.0100 (7) |
C7 | 0.0207 (8) | 0.0355 (10) | 0.0209 (8) | −0.0039 (7) | 0.0012 (7) | 0.0049 (7) |
C8 | 0.0237 (8) | 0.0265 (8) | 0.0257 (8) | −0.0004 (7) | 0.0014 (7) | 0.0011 (7) |
C9 | 0.0184 (8) | 0.0254 (8) | 0.0234 (8) | −0.0022 (7) | 0.0004 (6) | 0.0038 (7) |
N10 | 0.0225 (7) | 0.0237 (7) | 0.0221 (7) | −0.0001 (6) | 0.0002 (6) | 0.0013 (6) |
C11 | 0.0195 (8) | 0.0225 (8) | 0.0220 (8) | −0.0002 (6) | 0.0024 (6) | −0.0002 (6) |
C12 | 0.0225 (8) | 0.0248 (8) | 0.0246 (8) | −0.0003 (6) | 0.0000 (7) | −0.0019 (7) |
C13 | 0.0293 (9) | 0.0226 (8) | 0.0312 (9) | 0.0019 (7) | 0.0014 (7) | −0.0001 (7) |
C14 | 0.0258 (9) | 0.0310 (9) | 0.0263 (9) | 0.0045 (7) | −0.0004 (7) | 0.0068 (7) |
C15 | 0.0283 (10) | 0.0354 (9) | 0.0221 (8) | 0.0011 (8) | −0.0029 (7) | −0.0020 (7) |
C16 | 0.0258 (9) | 0.0245 (8) | 0.0272 (8) | −0.0004 (7) | 0.0006 (7) | −0.0031 (7) |
F17 | 0.0459 (7) | 0.0397 (6) | 0.0347 (6) | 0.0119 (5) | −0.0078 (5) | 0.0092 (5) |
C18 | 0.0219 (8) | 0.0235 (8) | 0.0262 (9) | 0.0030 (7) | −0.0012 (7) | 0.0001 (7) |
C19 | 0.0318 (10) | 0.0241 (9) | 0.0300 (9) | −0.0010 (7) | 0.0004 (8) | 0.0014 (7) |
C20 | 0.0444 (12) | 0.0253 (9) | 0.0323 (9) | −0.0019 (8) | −0.0002 (9) | −0.0058 (8) |
N21 | 0.0429 (10) | 0.0319 (8) | 0.0284 (8) | 0.0021 (7) | 0.0025 (7) | −0.0039 (7) |
C22 | 0.0369 (11) | 0.0293 (9) | 0.0288 (9) | −0.0010 (8) | 0.0053 (8) | 0.0017 (7) |
C23 | 0.0303 (9) | 0.0228 (8) | 0.0284 (9) | −0.0008 (7) | 0.0011 (7) | −0.0022 (7) |
O24 | 0.0350 (7) | 0.0406 (8) | 0.0216 (6) | 0.0003 (6) | −0.0003 (5) | 0.0052 (5) |
C25 | 0.0353 (11) | 0.0436 (11) | 0.0279 (9) | 0.0009 (9) | 0.0001 (8) | −0.0011 (8) |
C1—N10 | 1.324 (2) | C13—C14 | 1.381 (3) |
C1—C2 | 1.440 (2) | C13—H13 | 0.9500 |
C1—C11 | 1.482 (2) | C14—F17 | 1.356 (2) |
C2—N3 | 1.325 (2) | C14—C15 | 1.378 (3) |
C2—C18 | 1.486 (2) | C15—C16 | 1.387 (2) |
N3—C4 | 1.362 (2) | C15—H15 | 0.9500 |
C4—C5 | 1.414 (2) | C16—H16 | 0.9500 |
C4—C9 | 1.416 (2) | C18—C19 | 1.388 (2) |
C5—C6 | 1.360 (3) | C18—C23 | 1.391 (2) |
C5—H5 | 0.9500 | C19—C20 | 1.382 (3) |
C6—C7 | 1.423 (3) | C19—H19 | 0.9500 |
C6—H6 | 0.9500 | C20—N21 | 1.338 (3) |
C7—O24 | 1.363 (2) | C20—H20 | 0.9500 |
C7—C8 | 1.369 (2) | N21—C22 | 1.338 (2) |
C8—C9 | 1.410 (2) | C22—C23 | 1.384 (3) |
C8—H8 | 0.9500 | C22—H22 | 0.9500 |
C9—N10 | 1.363 (2) | C23—H23 | 0.9500 |
C11—C16 | 1.398 (2) | O24—C25 | 1.426 (2) |
C11—C12 | 1.400 (2) | C25—H25A | 0.9800 |
C12—C13 | 1.382 (2) | C25—H25B | 0.9800 |
C12—H12 | 0.9500 | C25—H25C | 0.9800 |
N10—C1—C2 | 120.82 (15) | C12—C13—H13 | 120.7 |
N10—C1—C11 | 115.80 (15) | F17—C14—C15 | 118.43 (16) |
C2—C1—C11 | 123.35 (15) | F17—C14—C13 | 118.67 (16) |
N3—C2—C1 | 121.23 (15) | C15—C14—C13 | 122.89 (16) |
N3—C2—C18 | 115.13 (15) | C14—C15—C16 | 117.77 (17) |
C1—C2—C18 | 123.52 (15) | C14—C15—H15 | 121.1 |
C2—N3—C4 | 117.89 (15) | C16—C15—H15 | 121.1 |
N3—C4—C5 | 120.10 (16) | C15—C16—C11 | 121.39 (16) |
N3—C4—C9 | 120.69 (15) | C15—C16—H16 | 119.3 |
C5—C4—C9 | 119.16 (16) | C11—C16—H16 | 119.3 |
C6—C5—C4 | 120.00 (17) | C19—C18—C23 | 117.26 (16) |
C6—C5—H5 | 120.0 | C19—C18—C2 | 121.15 (16) |
C4—C5—H5 | 120.0 | C23—C18—C2 | 121.47 (15) |
C5—C6—C7 | 120.69 (16) | C20—C19—C18 | 118.88 (17) |
C5—C6—H6 | 119.7 | C20—C19—H19 | 120.6 |
C7—C6—H6 | 119.7 | C18—C19—H19 | 120.6 |
O24—C7—C8 | 125.10 (17) | N21—C20—C19 | 124.49 (17) |
O24—C7—C6 | 114.32 (15) | N21—C20—H20 | 117.8 |
C8—C7—C6 | 120.58 (16) | C19—C20—H20 | 117.8 |
C7—C8—C9 | 119.36 (16) | C20—N21—C22 | 116.18 (16) |
C7—C8—H8 | 120.3 | N21—C22—C23 | 123.54 (17) |
C9—C8—H8 | 120.3 | N21—C22—H22 | 118.2 |
N10—C9—C8 | 119.04 (15) | C23—C22—H22 | 118.2 |
N10—C9—C4 | 120.78 (15) | C22—C23—C18 | 119.64 (16) |
C8—C9—C4 | 120.17 (15) | C22—C23—H23 | 120.2 |
C1—N10—C9 | 118.06 (15) | C18—C23—H23 | 120.2 |
C16—C11—C12 | 118.64 (16) | C7—O24—C25 | 116.56 (14) |
C16—C11—C1 | 122.23 (15) | O24—C25—H25A | 109.5 |
C12—C11—C1 | 119.03 (15) | O24—C25—H25B | 109.5 |
C13—C12—C11 | 120.66 (16) | H25A—C25—H25B | 109.5 |
C13—C12—H12 | 119.7 | O24—C25—H25C | 109.5 |
C11—C12—H12 | 119.7 | H25A—C25—H25C | 109.5 |
C14—C13—C12 | 118.61 (16) | H25B—C25—H25C | 109.5 |
C14—C13—H13 | 120.7 | ||
N10—C1—C2—N3 | 7.9 (3) | N10—C1—C11—C12 | 32.8 (2) |
C11—C1—C2—N3 | −170.22 (16) | C2—C1—C11—C12 | −149.01 (16) |
N10—C1—C2—C18 | −167.94 (16) | C16—C11—C12—C13 | −0.6 (3) |
C11—C1—C2—C18 | 13.9 (3) | C1—C11—C12—C13 | −177.19 (16) |
C1—C2—N3—C4 | −5.4 (2) | C11—C12—C13—C14 | −0.8 (3) |
C18—C2—N3—C4 | 170.78 (15) | C12—C13—C14—F17 | −177.56 (16) |
C2—N3—C4—C5 | −178.67 (16) | C12—C13—C14—C15 | 2.1 (3) |
C2—N3—C4—C9 | −1.1 (2) | F17—C14—C15—C16 | 177.79 (16) |
N3—C4—C5—C6 | 176.67 (16) | C13—C14—C15—C16 | −1.9 (3) |
C9—C4—C5—C6 | −1.0 (3) | C14—C15—C16—C11 | 0.4 (3) |
C4—C5—C6—C7 | −0.7 (3) | C12—C11—C16—C15 | 0.8 (3) |
C5—C6—C7—O24 | −178.82 (16) | C1—C11—C16—C15 | 177.30 (16) |
C5—C6—C7—C8 | 1.2 (3) | N3—C2—C18—C19 | 46.7 (2) |
O24—C7—C8—C9 | −179.94 (15) | C1—C2—C18—C19 | −137.24 (18) |
C6—C7—C8—C9 | 0.0 (3) | N3—C2—C18—C23 | −129.12 (18) |
C7—C8—C9—N10 | 177.21 (16) | C1—C2—C18—C23 | 47.0 (3) |
C7—C8—C9—C4 | −1.7 (3) | C23—C18—C19—C20 | −1.1 (3) |
N3—C4—C9—N10 | 5.7 (3) | C2—C18—C19—C20 | −177.09 (17) |
C5—C4—C9—N10 | −176.72 (16) | C18—C19—C20—N21 | 1.7 (3) |
N3—C4—C9—C8 | −175.42 (15) | C19—C20—N21—C22 | −1.0 (3) |
C5—C4—C9—C8 | 2.2 (3) | C20—N21—C22—C23 | −0.1 (3) |
C2—C1—N10—C9 | −3.2 (2) | N21—C22—C23—C18 | 0.6 (3) |
C11—C1—N10—C9 | 175.05 (14) | C19—C18—C23—C22 | 0.1 (3) |
C8—C9—N10—C1 | 177.83 (15) | C2—C18—C23—C22 | 176.04 (17) |
C4—C9—N10—C1 | −3.2 (2) | C8—C7—O24—C25 | −3.7 (3) |
N10—C1—C11—C16 | −143.69 (17) | C6—C7—O24—C25 | 176.37 (16) |
C2—C1—C11—C16 | 34.5 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
C15—H15···N21i | 0.95 | 2.44 | 3.368 (3) | 165 |
Symmetry code: (i) −x, −y, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C20H14FN3O |
Mr | 331.34 |
Crystal system, space group | Orthorhombic, Pbca |
Temperature (K) | 193 |
a, b, c (Å) | 7.3886 (4), 12.2071 (8), 34.562 (6) |
V (Å3) | 3117.3 (6) |
Z | 8 |
Radiation type | Cu Kα |
µ (mm−1) | 0.80 |
Crystal size (mm) | 0.45 × 0.22 × 0.13 |
Data collection | |
Diffractometer | Enraf–Nonius CAD-4 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2950, 2950, 2542 |
Rint | 0.000 |
(sin θ/λ)max (Å−1) | 0.610 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.044, 0.124, 1.05 |
No. of reflections | 2950 |
No. of parameters | 228 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.32, −0.24 |
Computer programs: CAD-4 Software (Enraf–Nonius, 1989), CORINC (Dräger & Gattow, 1971), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
C15—H15···N21i | 0.95 | 2.44 | 3.368 (3) | 165 |
Symmetry code: (i) −x, −y, −z+1. |
References
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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.
Functionalized quinoxaline derivatives are well known in pharmaceutical industry. They have been shown to possess antibacterial activity (Kim et al. 2004) and as PDGF-R tyrosine kinase inhibitors (He et al. 2003).
The title compound, (I), was prepared in the course of our studies on 2-(2-alkylaminopyridin-4-yl)-3-(4-fluorophenyl)quinoxalines as potent p38 mitogen-activated protein (MAP) kinase inhibitors. The two molecules of I are connected into a centrosymmetric dimer by intermolecular C15–H15···N21 hydrogen bonds [graph set R22(20) (Bernstein et al. 1995)] (Fig.1 and Table 1). By searching the CCDC a similar O—H···N hydrogen bond pattern could be found in the structure EHOTUQ (Friščič & MacGillivray 2003), with a R44(46) ring system. A variety of distinct ring motifs formed via hydrogen bonded donors and acceptors (O—H···O, O—H···N) has been described for the 4/1/2 adduct of benzene-1,3,5-tricarboxylic acid, 1,2-bis(1,2,4-triazol-4-yl)ethane and water by Habib & Janiak (2008). The C—H···N hydrogen bond of the title compound (Table 1) confirms the hydrogen-bond geometry values reviewed by Taylor & Kennard (1982), where the C—H···N distances vary between 2.523 Å and 2.721 Å, and the angles around the H atom range between 124.6° and 157.3°. The quinoxaline ring makes dihedral angles of 32.38 (7)° and 48.04 (7)° to the 4-fluorophenyl ring and the pyridine ring, respectively. The 4-fluorophenyl ring makes dihedral angles of 57.77 (9)° with the pyridine ring.
π—π interactions between the pyridin rings and the 4-fluorophenyl rings along the b axis have Cg2···Cg4ii distances of 3.823 (1) Å, and the distances between Cg3···Cg3iii of the methoxyphenyl rings are 3.720 (1) Å along the a axis (Fig. 2). The respective average perpendicular stacking distances are 3.378 Å and 3.421 Å, with dihedral angles between the rings 1.31° and 11.64°. Symmetry codes ii = 1/2 - x, 1/2 + y, z; iii = -1/2 + x y, 3/2 - z. Cg2, Cg3 and Cg4 are the centroids of rings N21, C20, C19, C18, C23, C22; C4 - C9; and C11 - C16.