organic compounds
Ethyl 2-(2-oxo-3-phenyl-1,2-dihydroquinoxalin-1-yl)acetate
aLaboratoire de Chimie Organique Hétérocyclique, Centre de Recherche des Sciences des Médicaments, URAC 21, Pôle de Compétence Pharmacochimie, Av Ibn Battouta, BP 1014, Faculté des Sciences, Université Mohammed V, Rabat, Morocco, bLaboratory of Medicinal Chemistry, Faculty of Medicine and Pharmacy, University Mohammed V, Rabat, Morocco, and cDepartment of Chemistry, Tulane University, New Orleans, LA 70118, USA
*Correspondence e-mail: ab.nadeem2018@gmail.com
In the title compound, C18H16N2O3, the dihydroquinoxaline moiety is planar (r.m.s. deviation = 0.0115 Å) and the majority of the ester substituent is nearly perpendicular to its mean plane. In the crystal, the molecules form oblique stacks along the b-axis direction through slipped π–π stacking interactions between adjacent dihydroquinoxaline units. C—H⋯O hydrogen bonds between the ester substituents on adjacent stacks form thick layers with the stacks on their outside surfaces. These layers extend along the c-axis direction and are coupled through C—H⋯π(ring) interactions. The structure was refined as a two-component twin.
Keywords: crystal structure; hydrogen bond; π-stacking; dihydroquinoxaline.
CCDC reference: 1834198
Structure description
Quinoxaline derivatives are important compounds in medicinal chemistry possessing a wide variety of biological properties such as anticancer (Abbas et al., 2015; Ingle et al., 2013), antimicrobial (Attia et al., 2013; Vieira et al., 2014; Teja et al., 2016), anti-inflammatory (Guirado et al., 2012; Burguete et al., 2001), antidepressant (Mahesh et al., 2011), antiviral (Henen et al., 2012; El-Tombary & El-Hawash, 2014), antidiabetic (Kulkarni et al., 2012), antihypertensive (Gupta et al., 2011) and antihistaminic activities (Sridevi et al., 2010). In addition, it has been reported that the quinoxaline moiety is also an integral part of natural and synthetic antibiotics such as triostin A and echinomycin, known to inhibit the growth of Gram positive bacteria. As a continuation of our studies of quinoxaline derivatives (Ramli et al., 2018), we report the synthesis and structure of the title compound (Fig. 1).
The dihydroquinoxaline moiety is planar to within 0.0221 (13) Å (r.m.s. deviation = 0.0115 Å). The pendant phenyl ring is inclined to this plane by 19.63 (7)°, while the N2/C15/C16/C17/O2/O3 unit, which is planar to within 0.0078 (16) Å (r.m.s. deviation = 0.005 Å), is inclined by 88.62 (7)°. In the crystal, the molecules form oblique stacks along the b-axis direction through slipped π–π-stacking interactions between the C1–C6 and C1/C6/N1/C7/C8/N2 rings with centroid–centroid separations of 3.8364 (10) Å. This is reinforced by C2—H2⋯O2 hydrogen bonds. Adjacent stacks are associated by C17—H17B⋯O2 and C18—H18B⋯O3 interactions, forming thick layers extending along the c-axis direction (Table 1 and Fig. 2). Finally, these layers are `stitched' together by a series of C12—H12⋯Cg3 interactions (Table 1 and Fig. 3; Cg3 is the centroid of ring C9–C14).
Synthesis and crystallization
To a solution of 2-oxo-3-phenyl-1,2-dihydroquinoxaline (0.7 g, 3 mmol) in N,N-dimethylformamide (20 ml) were added ethyl bromoacetate (0.25 ml, 2.25 mmol), potassium carbonate K2CO3 (0.1 g, 2.25 mmol) and a catalytic quantity of tetra-n-butylammonium bromide. The mixture was stirred at room temperature for 12 h. The solution was filtered and the solvent removed under reduced pressure. The residue obtained, after evaporation of solvent, was chromatographed on a silica gel column using a hexane/ethyl acetate 9:1 mixture as The solid obtained was recrystallized from ethanol to afford colourless crystals (yield: 90%).
Refinement
Crystal data, data collection and structure . The structure was refined as a two-component twin.
details are summarized in Table 2
|
Structural data
CCDC reference: 1834198
https://doi.org/10.1107/S2414314618005199/vm4035sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314618005199/vm4035Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2414314618005199/vm4035Isup3.cdx
Supporting information file. DOI: https://doi.org/10.1107/S2414314618005199/vm4035Isup4.cml
Data collection: APEX3 (Bruker, 2016); cell
SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016) and CELL_NOW (Sheldrick, 2008a); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: DIAMOND (Brandenburg & Putz, 2012); software used to prepare material for publication: SHELXTL (Sheldrick, 2008b).C18H16N2O3 | F(000) = 648 |
Mr = 308.33 | Dx = 1.357 Mg m−3 |
Monoclinic, P21/c | Cu Kα radiation, λ = 1.54178 Å |
a = 18.1710 (5) Å | Cell parameters from 9923 reflections |
b = 4.9012 (1) Å | θ = 2.4–72.4° |
c = 16.9492 (5) Å | µ = 0.77 mm−1 |
β = 91.923 (1)° | T = 150 K |
V = 1508.64 (7) Å3 | Plate, colourless |
Z = 4 | 0.32 × 0.11 × 0.04 mm |
Bruker D8 VENTURE PHOTON 100 CMOS diffractometer | 19783 independent reflections |
Radiation source: INCOATEC IµS micro-focus source | 14579 reflections with I > 2σ(I) |
Mirror monochromator | Rint = 0.030 |
Detector resolution: 10.4167 pixels mm-1 | θmax = 72.4°, θmin = 2.4° |
ω scans | h = −22→21 |
Absorption correction: multi-scan (TWINABS; Sheldrick, 2009) | k = −6→5 |
Tmin = 0.79, Tmax = 0.97 | l = −20→20 |
19783 measured reflections |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.046 | All H-atom parameters refined |
wR(F2) = 0.121 | w = 1/[σ2(Fo2) + (0.0459P)2 + 0.2438P] where P = (Fo2 + 2Fc2)/3 |
S = 1.01 | (Δ/σ)max < 0.001 |
19783 reflections | Δρmax = 0.20 e Å−3 |
274 parameters | Δρmin = −0.24 e Å−3 |
0 restraints | Extinction correction: SHELXTL (Sheldrick, 2008b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0050 (8) |
Experimental. Analysis of 1517 reflections having I/σ(I) > 12 and chosen from the full data set with CELL_NOW (Sheldrick, 2008) showed the crystal to belong to the monoclinic system and to consist of two components related by a 35.5° rotation about the b axis. The raw data were processed using the multi-component version ofSAINT under control of the two-component orientation filegenerated by CELL_NOW. |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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. Refined as a 2-component twin. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.25922 (7) | 0.7640 (3) | 0.31580 (8) | 0.0417 (4) | |
O2 | 0.41992 (7) | 0.6916 (3) | 0.43879 (8) | 0.0438 (4) | |
O3 | 0.46812 (6) | 0.4139 (3) | 0.34884 (7) | 0.0364 (3) | |
N1 | 0.15573 (8) | 0.6338 (3) | 0.48696 (8) | 0.0277 (3) | |
N2 | 0.28105 (7) | 0.4569 (3) | 0.41319 (8) | 0.0285 (3) | |
C1 | 0.26404 (9) | 0.3412 (3) | 0.48550 (10) | 0.0282 (4) | |
C2 | 0.30684 (10) | 0.1373 (4) | 0.52219 (11) | 0.0352 (4) | |
H2 | 0.3510 (13) | 0.067 (4) | 0.4983 (13) | 0.043 (6)* | |
C3 | 0.28523 (11) | 0.0297 (4) | 0.59278 (12) | 0.0395 (4) | |
H3 | 0.3145 (13) | −0.117 (5) | 0.6175 (13) | 0.050 (6)* | |
C4 | 0.22231 (11) | 0.1216 (4) | 0.62916 (11) | 0.0393 (4) | |
H4 | 0.2080 (12) | 0.036 (5) | 0.6796 (14) | 0.045 (6)* | |
C5 | 0.18037 (10) | 0.3237 (4) | 0.59365 (11) | 0.0348 (4) | |
H5 | 0.1341 (12) | 0.395 (4) | 0.6164 (12) | 0.041 (5)* | |
C6 | 0.20033 (9) | 0.4357 (3) | 0.52132 (9) | 0.0280 (4) | |
C7 | 0.17228 (9) | 0.7415 (3) | 0.41992 (9) | 0.0260 (4) | |
C8 | 0.23990 (9) | 0.6628 (3) | 0.37802 (10) | 0.0294 (4) | |
C9 | 0.11989 (9) | 0.9429 (3) | 0.38455 (9) | 0.0268 (4) | |
C10 | 0.04810 (10) | 0.9459 (4) | 0.41234 (10) | 0.0308 (4) | |
H10 | 0.0352 (11) | 0.811 (4) | 0.4512 (12) | 0.038 (5)* | |
C11 | −0.00326 (10) | 1.1326 (4) | 0.38378 (10) | 0.0335 (4) | |
H11 | −0.0533 (13) | 1.128 (4) | 0.4046 (12) | 0.040 (5)* | |
C12 | 0.01550 (10) | 1.3195 (4) | 0.32662 (10) | 0.0339 (4) | |
H12 | −0.0217 (12) | 1.452 (4) | 0.3059 (12) | 0.036 (5)* | |
C13 | 0.08591 (10) | 1.3174 (4) | 0.29784 (10) | 0.0332 (4) | |
H13 | 0.1002 (11) | 1.449 (4) | 0.2570 (12) | 0.039 (5)* | |
C14 | 0.13792 (10) | 1.1303 (3) | 0.32583 (10) | 0.0299 (4) | |
H14 | 0.1874 (12) | 1.132 (4) | 0.3037 (12) | 0.040 (5)* | |
C15 | 0.34349 (10) | 0.3597 (4) | 0.36944 (11) | 0.0324 (4) | |
H15A | 0.3325 (12) | 0.389 (5) | 0.3142 (15) | 0.046 (6)* | |
H15B | 0.3514 (12) | 0.167 (5) | 0.3776 (12) | 0.040 (5)* | |
C16 | 0.41371 (9) | 0.5107 (3) | 0.39143 (10) | 0.0297 (4) | |
C17 | 0.54066 (10) | 0.5371 (5) | 0.36140 (13) | 0.0422 (5) | |
H17A | 0.5341 (14) | 0.739 (6) | 0.3615 (15) | 0.062 (7)* | |
H17B | 0.5591 (13) | 0.475 (5) | 0.4136 (14) | 0.047 (6)* | |
C18 | 0.58651 (11) | 0.4416 (5) | 0.29504 (12) | 0.0407 (5) | |
H18A | 0.6373 (14) | 0.517 (5) | 0.3032 (14) | 0.052 (6)* | |
H18B | 0.5656 (14) | 0.506 (5) | 0.2434 (16) | 0.058 (7)* | |
H18C | 0.5870 (13) | 0.234 (5) | 0.2945 (13) | 0.049 (6)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0402 (8) | 0.0435 (8) | 0.0427 (7) | 0.0049 (6) | 0.0176 (6) | 0.0057 (6) |
O2 | 0.0317 (7) | 0.0435 (8) | 0.0567 (8) | −0.0015 (6) | 0.0059 (6) | −0.0212 (6) |
O3 | 0.0226 (6) | 0.0414 (7) | 0.0457 (7) | −0.0027 (5) | 0.0081 (5) | −0.0121 (5) |
N1 | 0.0241 (7) | 0.0285 (7) | 0.0306 (7) | 0.0023 (6) | 0.0025 (5) | −0.0011 (5) |
N2 | 0.0208 (7) | 0.0292 (7) | 0.0357 (7) | 0.0009 (6) | 0.0047 (6) | −0.0064 (6) |
C1 | 0.0241 (8) | 0.0259 (8) | 0.0345 (8) | −0.0009 (6) | −0.0003 (7) | −0.0063 (6) |
C2 | 0.0271 (9) | 0.0319 (9) | 0.0465 (10) | 0.0047 (7) | −0.0029 (8) | −0.0067 (7) |
C3 | 0.0369 (11) | 0.0332 (10) | 0.0477 (11) | 0.0064 (8) | −0.0097 (8) | 0.0004 (8) |
C4 | 0.0419 (11) | 0.0375 (10) | 0.0382 (10) | 0.0031 (8) | −0.0017 (8) | 0.0049 (8) |
C5 | 0.0328 (10) | 0.0363 (9) | 0.0354 (9) | 0.0040 (8) | 0.0030 (7) | 0.0016 (7) |
C6 | 0.0246 (8) | 0.0268 (8) | 0.0327 (8) | 0.0018 (7) | 0.0000 (6) | −0.0031 (6) |
C7 | 0.0237 (8) | 0.0249 (8) | 0.0296 (8) | −0.0015 (6) | 0.0023 (6) | −0.0043 (6) |
C8 | 0.0254 (8) | 0.0293 (9) | 0.0336 (9) | −0.0018 (7) | 0.0048 (7) | −0.0041 (6) |
C9 | 0.0263 (8) | 0.0260 (8) | 0.0279 (8) | 0.0006 (7) | 0.0000 (6) | −0.0048 (6) |
C10 | 0.0294 (9) | 0.0320 (9) | 0.0310 (8) | 0.0029 (7) | 0.0030 (7) | −0.0009 (7) |
C11 | 0.0290 (9) | 0.0374 (10) | 0.0340 (9) | 0.0060 (7) | 0.0007 (7) | −0.0032 (7) |
C12 | 0.0359 (10) | 0.0316 (9) | 0.0337 (9) | 0.0065 (8) | −0.0062 (7) | −0.0035 (7) |
C13 | 0.0378 (10) | 0.0297 (9) | 0.0317 (9) | −0.0025 (7) | −0.0037 (7) | 0.0006 (7) |
C14 | 0.0296 (9) | 0.0297 (9) | 0.0302 (8) | −0.0040 (7) | −0.0006 (7) | −0.0029 (6) |
C15 | 0.0240 (9) | 0.0326 (10) | 0.0409 (10) | 0.0018 (7) | 0.0071 (7) | −0.0097 (7) |
C16 | 0.0251 (9) | 0.0290 (8) | 0.0352 (8) | 0.0036 (7) | 0.0043 (7) | −0.0031 (7) |
C17 | 0.0234 (9) | 0.0502 (12) | 0.0533 (12) | −0.0070 (8) | 0.0052 (8) | −0.0082 (9) |
C18 | 0.0258 (10) | 0.0550 (13) | 0.0415 (10) | 0.0020 (9) | 0.0049 (8) | 0.0111 (9) |
O1—C8 | 1.227 (2) | C9—C10 | 1.402 (2) |
O2—C16 | 1.199 (2) | C9—C14 | 1.401 (2) |
O3—C16 | 1.3311 (19) | C10—C11 | 1.383 (3) |
O3—C17 | 1.459 (2) | C10—H10 | 0.97 (2) |
N1—C7 | 1.297 (2) | C11—C12 | 1.384 (3) |
N1—C6 | 1.381 (2) | C11—H11 | 0.99 (2) |
N2—C8 | 1.379 (2) | C12—C13 | 1.385 (3) |
N2—C1 | 1.395 (2) | C12—H12 | 0.99 (2) |
N2—C15 | 1.456 (2) | C13—C14 | 1.389 (3) |
C1—C2 | 1.399 (3) | C13—H13 | 0.99 (2) |
C1—C6 | 1.404 (2) | C14—H14 | 0.99 (2) |
C2—C3 | 1.377 (3) | C15—C16 | 1.511 (2) |
C2—H2 | 0.97 (2) | C15—H15A | 0.96 (2) |
C3—C4 | 1.392 (3) | C15—H15B | 0.96 (2) |
C3—H3 | 0.98 (2) | C17—C18 | 1.497 (3) |
C4—C5 | 1.376 (3) | C17—H17A | 1.00 (3) |
C4—H4 | 0.99 (2) | C17—H17B | 0.98 (2) |
C5—C6 | 1.402 (2) | C18—H18A | 1.00 (2) |
C5—H5 | 1.00 (2) | C18—H18B | 0.99 (3) |
C7—C9 | 1.484 (2) | C18—H18C | 1.02 (3) |
C7—C8 | 1.490 (2) | ||
C16—O3—C17 | 117.19 (14) | C9—C10—H10 | 118.1 (12) |
C7—N1—C6 | 120.36 (14) | C10—C11—C12 | 120.25 (17) |
C8—N2—C1 | 122.99 (13) | C10—C11—H11 | 118.7 (12) |
C8—N2—C15 | 116.08 (14) | C12—C11—H11 | 121.1 (12) |
C1—N2—C15 | 120.92 (15) | C11—C12—C13 | 119.59 (17) |
N2—C1—C2 | 123.01 (15) | C11—C12—H12 | 120.0 (12) |
N2—C1—C6 | 117.13 (15) | C13—C12—H12 | 120.4 (12) |
C2—C1—C6 | 119.86 (16) | C12—C13—C14 | 120.72 (16) |
C3—C2—C1 | 119.29 (17) | C12—C13—H13 | 120.7 (12) |
C3—C2—H2 | 119.3 (13) | C14—C13—H13 | 118.6 (12) |
C1—C2—H2 | 121.4 (13) | C13—C14—C9 | 120.18 (16) |
C2—C3—C4 | 121.57 (17) | C13—C14—H14 | 118.8 (12) |
C2—C3—H3 | 119.0 (13) | C9—C14—H14 | 121.0 (12) |
C4—C3—H3 | 119.4 (13) | N2—C15—C16 | 112.34 (14) |
C5—C4—C3 | 119.35 (18) | N2—C15—H15A | 107.9 (13) |
C5—C4—H4 | 121.5 (13) | C16—C15—H15A | 108.3 (14) |
C3—C4—H4 | 119.1 (13) | N2—C15—H15B | 111.2 (13) |
C4—C5—C6 | 120.56 (17) | C16—C15—H15B | 108.9 (13) |
C4—C5—H5 | 122.9 (12) | H15A—C15—H15B | 108.1 (18) |
C6—C5—H5 | 116.5 (12) | O2—C16—O3 | 124.89 (16) |
N1—C6—C5 | 118.60 (15) | O2—C16—C15 | 125.96 (15) |
N1—C6—C1 | 122.05 (15) | O3—C16—C15 | 109.15 (14) |
C5—C6—C1 | 119.35 (16) | O3—C17—C18 | 106.48 (16) |
N1—C7—C9 | 117.39 (14) | O3—C17—H17A | 107.7 (15) |
N1—C7—C8 | 122.08 (15) | C18—C17—H17A | 112.4 (15) |
C9—C7—C8 | 120.51 (14) | O3—C17—H17B | 106.3 (13) |
O1—C8—N2 | 120.03 (15) | C18—C17—H17B | 113.4 (13) |
O1—C8—C7 | 124.68 (16) | H17A—C17—H17B | 110 (2) |
N2—C8—C7 | 115.28 (14) | C17—C18—H18A | 108.4 (14) |
C10—C9—C14 | 118.30 (15) | C17—C18—H18B | 110.8 (14) |
C10—C9—C7 | 117.58 (14) | H18A—C18—H18B | 109.1 (19) |
C14—C9—C7 | 124.11 (15) | C17—C18—H18C | 108.9 (13) |
C11—C10—C9 | 120.94 (16) | H18A—C18—H18C | 111.2 (19) |
C11—C10—H10 | 120.9 (13) | H18B—C18—H18C | 108.3 (19) |
C8—N2—C1—C2 | −178.28 (16) | N1—C7—C8—O1 | −177.72 (16) |
C15—N2—C1—C2 | 3.2 (2) | C9—C7—C8—O1 | 4.1 (3) |
C8—N2—C1—C6 | 2.4 (2) | N1—C7—C8—N2 | 3.6 (2) |
C15—N2—C1—C6 | −176.20 (15) | C9—C7—C8—N2 | −174.59 (14) |
N2—C1—C2—C3 | −178.57 (16) | N1—C7—C9—C10 | −18.0 (2) |
C6—C1—C2—C3 | 0.8 (3) | C8—C7—C9—C10 | 160.34 (15) |
C1—C2—C3—C4 | −0.9 (3) | N1—C7—C9—C14 | 161.55 (15) |
C2—C3—C4—C5 | 0.4 (3) | C8—C7—C9—C14 | −20.1 (2) |
C3—C4—C5—C6 | 0.3 (3) | C14—C9—C10—C11 | −1.3 (2) |
C7—N1—C6—C5 | −179.75 (16) | C7—C9—C10—C11 | 178.23 (15) |
C7—N1—C6—C1 | −0.7 (2) | C9—C10—C11—C12 | 0.4 (3) |
C4—C5—C6—N1 | 178.56 (16) | C10—C11—C12—C13 | 0.4 (3) |
C4—C5—C6—C1 | −0.5 (3) | C11—C12—C13—C14 | −0.2 (3) |
N2—C1—C6—N1 | 0.3 (2) | C12—C13—C14—C9 | −0.8 (3) |
C2—C1—C6—N1 | −179.10 (15) | C10—C9—C14—C13 | 1.5 (2) |
N2—C1—C6—C5 | 179.30 (15) | C7—C9—C14—C13 | −177.98 (15) |
C2—C1—C6—C5 | −0.1 (2) | C8—N2—C15—C16 | 91.54 (19) |
C6—N1—C7—C9 | 176.98 (14) | C1—N2—C15—C16 | −89.81 (19) |
C6—N1—C7—C8 | −1.3 (2) | C17—O3—C16—O2 | 0.4 (3) |
C1—N2—C8—O1 | 177.16 (15) | C17—O3—C16—C15 | 179.47 (16) |
C15—N2—C8—O1 | −4.2 (2) | N2—C15—C16—O2 | −0.3 (3) |
C1—N2—C8—C7 | −4.1 (2) | N2—C15—C16—O3 | −179.37 (15) |
C15—N2—C8—C7 | 174.49 (14) | C16—O3—C17—C18 | −167.13 (16) |
Cg3 is the centroid of the C9–C14 ring. |
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H2···O2i | 0.97 (2) | 2.46 (2) | 3.345 (2) | 150.7 (17) |
C17—H17B···O2ii | 0.98 (2) | 2.65 (2) | 3.616 (3) | 168.4 (18) |
C18—H18B···O3iii | 0.99 (3) | 2.60 (3) | 3.482 (2) | 148.3 (19) |
C12—H12···Cg3iv | 0.99 (2) | 2.96 (2) | 3.713 (2) | 133.4 (15) |
Symmetry codes: (i) x, y−1, z; (ii) −x+1, −y+1, −z+1; (iii) −x+1, y+1/2, −z+1/2; (iv) −x, y+1/2, −z+1/2. |
Funding information
The support of NSF–MRI Grant No. 1228232 for the purchase of the diffractometer and Tulane University for support of the Tulane Crystallography Laboratory are gratefully acknowledged.
References
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