organic compounds
7-Bromo-1,4-dibutyl-1,2,3,4-tetrahydropyrido[2,3-b]pyrazine-2,3-dione
aLaboratoire de Chimie Organique Appliquée, Université Sidi Mohamed Ben Abdallah, Faculté des Sciences et Techniques, Route d'Imouzzer, BP 2202, Fez, Morocco, bDepartment of Chemistry, Tulane University, New Orleans, LA 70118, USA, and cLaboratoire de Chimie Organique Hétérocyclique URAC 21, Pôle de, Compétence Pharmacochimie, Av. Ibn Battouta, BP 1014, Faculté des Sciences, Université Mohammed V, Rabat, Morocco
*Correspondence e-mail: younes.ouzidan@usmba.ac.ma
In the title compound, C15H20BrN3O2, the butyl substituents are in extended conformations on opposite sides of the bicyclic core. In the crystal, oblique stacks of molecules, formed by offset π-stacking interactions between pyridine and pyrazine rings in adjacent molecules, extend along the b-axis direction. The stacks are associated through a combination of C—H⋯O hydrogen bonds and C—Br⋯π(ring) interactions.
Keywords: crystal structure; pyridopyrazine; hydrogen bond; π-stacking.
CCDC reference: 1559996
Structure description
Pyrido-pyrazine derivatives are a versatile class of nitrogen-containing et al., 2011), anti-inflammatory (Hodgetts et al., 2010) and antimalarial (Richter et al., 2006). They are also used as inhibitors of anaplastic lymphoma kinase (Milkiewicz et al., 2010). As a continuation of our research in the field of substituted pyrido[2,3-b]pyrazine derivatives (Hjouji et al., 2014), we report here the synthesis of the title compound by the condensation of butyl bromide and 7-bromopyrido[2,3-b]pyrazine-2,3(1H,4H)-dione.
and they constitute useful intermediates in organic synthesis and medicinal chemistry. They possess a broad spectrum of biological activities including anti-cancer (GongIn the title molecule, the n-butyl substituents are both in extended conformations with one extending above and the other below the pyrazine ring (Fig. 1). The bicyclic core is planar within experimental error.
In the crystal, the molecules form oblique stacks along the b-axis direction through offset π-stacking interactions between the pyridine portion of one molecule and the pyrazine portion of the next (Fig. 2). In the stack, the centroid–centroid distance of the respective rings is 3.695 (5) Å and they are parallel within experimental error. Assisting these interactions in forming the stacks are π interactions between the C7O2 carbonyl group and the pyridine ring in adjacent molecules (Fig. 2) where the distance between the mid-point of the double bond and the ring centroid is 3.268 (8) Å. Finally, the stacks are associated through a combination of C2—H2⋯O1 and C12—H12A⋯O1 hydrogen bonds (Table 1 and Fig. 3) and C3—Br1⋯π(ring)i interactions (Fig. 2) where Br1⋯Cg2 = 3.701 (4) Å, C3—Br1⋯Cg2 = 118.1 (3)° and Cg2 is the centroid of the pyrazine portion of the molecule with symmetry code (i) − x, − + y, − + z).
Synthesis and crystallization
Butyl bromide (0.2 ml, 1.82 mmol) was added to a solution of 7-bromopyrido[2,3-b]pyrazine-2,3(1H,4H)-dione (0.2 g, 0.83 mmol), K2CO3 (0.28 g, 2.07 mmol) and tetra-n-butyl ammonium bromide (0.03 g, 0.1 mmol) in DMF (10 ml). The mixture was then stirred for 6 h at room temperature. The solvent was evaporated under reduced pressure and the product isolated by on a silica gel column with ethyl acetate/hexane (1/2) as The compound forms pale-blue plate-shaped crystals in 77% yield and was recrystallized from a solvent mixture (ethanol/dichloromethane: 2/1).
Refinement
Crystal and . The hydrogen atoms were included as riding contributions in idealized positions.
details are presented in Table 2Structural data
CCDC reference: 1559996
https://doi.org/10.1107/S2414314617009841/zq4022sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314617009841/zq4022Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2414314617009841/zq4022Isup3.cdx
Supporting information file. DOI: https://doi.org/10.1107/S2414314617009841/zq4022Isup4.cml
Data collection: APEX3 (Bruker, 2016); cell
SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: DIAMOND (Brandenburg & Putz, 2012); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).C15H20BrN3O2 | Dx = 1.512 Mg m−3 |
Mr = 354.25 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, Pna21 | Cell parameters from 3677 reflections |
a = 22.569 (6) Å | θ = 2.4–26.1° |
b = 5.1097 (13) Å | µ = 2.65 mm−1 |
c = 13.497 (3) Å | T = 100 K |
V = 1556.5 (7) Å3 | Plate, pale blue |
Z = 4 | 0.22 × 0.21 × 0.02 mm |
F(000) = 728 |
Bruker SMART APEX CCD diffractometer | 3859 independent reflections |
Radiation source: fine-focus sealed tube | 2916 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.091 |
Detector resolution: 8.3333 pixels mm-1 | θmax = 28.7°, θmin = 1.8° |
ω scans | h = −29→29 |
Absorption correction: multi-scan (SADABS; Bruker, 2016) | k = −6→6 |
Tmin = 0.50, Tmax = 0.96 | l = −18→17 |
13413 measured reflections |
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)] = 0.068 | H-atom parameters constrained |
wR(F2) = 0.156 | w = 1/[σ2(Fo2) + 6.1176P] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max < 0.001 |
3859 reflections | Δρmax = 2.33 e Å−3 |
192 parameters | Δρmin = −1.38 e Å−3 |
94 restraints | Absolute structure: Flack x determined using 1091 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013) |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.038 (15) |
Experimental. The diffraction data were collected in three sets of 363 frames (0.5° width in ω) at φ = 0, 120 and 240°. A scan time of 80 sec/frame was used. |
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. H-atoms attached to carbon were placed in calculated positions (C—H = 0.95 - 0.99 Å). All were included as riding contributions with isotropic displacement parameters 1.2 - 1.5 times those of the attached atoms. |
x | y | z | Uiso*/Ueq | ||
Br1 | 0.30633 (4) | −0.15545 (15) | 0.26770 (7) | 0.0209 (2) | |
O1 | 0.3211 (3) | 0.8535 (14) | 0.7274 (5) | 0.0249 (16) | |
O2 | 0.2233 (3) | 0.9499 (14) | 0.6151 (5) | 0.0249 (16) | |
N1 | 0.3741 (4) | 0.1719 (16) | 0.5238 (6) | 0.0203 (16) | |
N2 | 0.3449 (4) | 0.5053 (15) | 0.6305 (5) | 0.0180 (16) | |
N3 | 0.2463 (4) | 0.6115 (14) | 0.5112 (6) | 0.0158 (15) | |
C1 | 0.2854 (4) | 0.4141 (18) | 0.4835 (7) | 0.0168 (18) | |
C2 | 0.2764 (5) | 0.259 (2) | 0.4013 (7) | 0.0191 (19) | |
H2 | 0.2422 | 0.2821 | 0.3612 | 0.023* | |
C3 | 0.3178 (4) | 0.0675 (19) | 0.3780 (6) | 0.0193 (19) | |
C4 | 0.3653 (4) | 0.0215 (19) | 0.4425 (6) | 0.0184 (19) | |
H4 | 0.3920 | −0.1180 | 0.4289 | 0.022* | |
C5 | 0.3348 (5) | 0.3572 (18) | 0.5437 (6) | 0.0172 (17) | |
C6 | 0.3103 (4) | 0.7138 (17) | 0.6563 (7) | 0.0168 (18) | |
C7 | 0.2560 (5) | 0.7737 (18) | 0.5913 (7) | 0.0185 (18) | |
C8 | 0.3954 (4) | 0.4332 (19) | 0.6961 (7) | 0.021 (2) | |
H8A | 0.4020 | 0.2419 | 0.6924 | 0.026* | |
H8B | 0.3854 | 0.4776 | 0.7655 | 0.026* | |
C9 | 0.4524 (5) | 0.576 (2) | 0.6662 (7) | 0.024 (2) | |
H9A | 0.4622 | 0.5355 | 0.5963 | 0.029* | |
H9B | 0.4464 | 0.7678 | 0.6717 | 0.029* | |
C10 | 0.5036 (5) | 0.493 (2) | 0.7330 (8) | 0.028 (2) | |
H10A | 0.4924 | 0.5245 | 0.8029 | 0.033* | |
H10B | 0.5103 | 0.3028 | 0.7248 | 0.033* | |
C11 | 0.5613 (5) | 0.637 (2) | 0.7113 (10) | 0.036 (3) | |
H11A | 0.5737 | 0.6012 | 0.6431 | 0.055* | |
H11B | 0.5921 | 0.5770 | 0.7572 | 0.055* | |
H11C | 0.5552 | 0.8256 | 0.7198 | 0.055* | |
C12 | 0.1912 (4) | 0.661 (2) | 0.4538 (7) | 0.0200 (19) | |
H12A | 0.1987 | 0.6253 | 0.3827 | 0.024* | |
H12B | 0.1799 | 0.8473 | 0.4605 | 0.024* | |
C13 | 0.1406 (4) | 0.4884 (19) | 0.4902 (7) | 0.021 (2) | |
H13A | 0.1526 | 0.3026 | 0.4847 | 0.026* | |
H13B | 0.1331 | 0.5262 | 0.5610 | 0.026* | |
C14 | 0.0842 (5) | 0.530 (2) | 0.4327 (7) | 0.025 (2) | |
H14A | 0.0908 | 0.4771 | 0.3630 | 0.031* | |
H14B | 0.0743 | 0.7186 | 0.4331 | 0.031* | |
C15 | 0.0318 (5) | 0.377 (2) | 0.4738 (8) | 0.030 (2) | |
H15A | −0.0025 | 0.3997 | 0.4302 | 0.046* | |
H15B | 0.0221 | 0.4411 | 0.5403 | 0.046* | |
H15C | 0.0420 | 0.1905 | 0.4774 | 0.046* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Br1 | 0.0338 (5) | 0.0191 (4) | 0.0099 (3) | 0.0011 (4) | 0.0012 (6) | −0.0072 (5) |
O1 | 0.035 (4) | 0.027 (4) | 0.012 (3) | −0.005 (3) | 0.002 (3) | −0.013 (3) |
O2 | 0.035 (4) | 0.020 (4) | 0.020 (4) | 0.003 (3) | 0.004 (3) | −0.002 (3) |
N1 | 0.024 (4) | 0.022 (4) | 0.015 (3) | 0.002 (3) | −0.002 (3) | 0.000 (3) |
N2 | 0.029 (4) | 0.016 (4) | 0.009 (3) | −0.003 (3) | −0.001 (3) | −0.005 (3) |
N3 | 0.025 (4) | 0.012 (3) | 0.010 (3) | −0.001 (3) | 0.001 (3) | −0.003 (3) |
C1 | 0.023 (4) | 0.016 (4) | 0.011 (4) | 0.001 (3) | 0.002 (3) | −0.002 (3) |
C2 | 0.028 (5) | 0.019 (4) | 0.010 (4) | −0.001 (4) | 0.000 (4) | 0.000 (3) |
C3 | 0.030 (5) | 0.021 (4) | 0.007 (4) | −0.001 (3) | 0.004 (3) | −0.002 (3) |
C4 | 0.028 (5) | 0.018 (4) | 0.010 (4) | 0.001 (4) | 0.001 (3) | −0.002 (3) |
C5 | 0.025 (4) | 0.018 (4) | 0.009 (3) | 0.000 (3) | 0.000 (3) | −0.002 (3) |
C6 | 0.029 (4) | 0.010 (4) | 0.011 (3) | −0.004 (3) | 0.001 (3) | −0.002 (3) |
C7 | 0.029 (5) | 0.018 (4) | 0.009 (3) | −0.001 (3) | 0.001 (3) | 0.000 (3) |
C8 | 0.030 (6) | 0.025 (5) | 0.009 (4) | −0.002 (4) | −0.002 (4) | −0.005 (4) |
C9 | 0.031 (6) | 0.023 (5) | 0.017 (5) | 0.000 (4) | −0.002 (4) | 0.001 (4) |
C10 | 0.036 (6) | 0.024 (5) | 0.023 (5) | −0.001 (4) | −0.005 (4) | −0.001 (4) |
C11 | 0.031 (6) | 0.031 (6) | 0.047 (7) | 0.001 (5) | −0.009 (5) | 0.003 (5) |
C12 | 0.023 (5) | 0.025 (5) | 0.013 (4) | 0.002 (4) | −0.005 (4) | −0.001 (4) |
C13 | 0.026 (6) | 0.022 (5) | 0.016 (5) | 0.005 (4) | 0.000 (4) | 0.006 (4) |
C14 | 0.034 (6) | 0.025 (5) | 0.017 (5) | 0.002 (5) | 0.001 (4) | −0.002 (4) |
C15 | 0.031 (6) | 0.036 (6) | 0.024 (5) | −0.003 (5) | 0.001 (5) | −0.006 (5) |
Br1—C3 | 1.892 (9) | C9—C10 | 1.527 (15) |
O1—C6 | 1.221 (11) | C9—H9A | 0.9900 |
O2—C7 | 1.207 (12) | C9—H9B | 0.9900 |
N1—C5 | 1.325 (12) | C10—C11 | 1.523 (15) |
N1—C4 | 1.354 (12) | C10—H10A | 0.9900 |
N2—C6 | 1.365 (12) | C10—H10B | 0.9900 |
N2—C5 | 1.414 (11) | C11—H11A | 0.9800 |
N2—C8 | 1.489 (12) | C11—H11B | 0.9800 |
N3—C7 | 1.379 (12) | C11—H11C | 0.9800 |
N3—C1 | 1.392 (11) | C12—C13 | 1.525 (14) |
N3—C12 | 1.487 (12) | C12—H12A | 0.9900 |
C1—C2 | 1.380 (13) | C12—H12B | 0.9900 |
C1—C5 | 1.408 (14) | C13—C14 | 1.506 (14) |
C2—C3 | 1.388 (14) | C13—H13A | 0.9900 |
C2—H2 | 0.9500 | C13—H13B | 0.9900 |
C3—C4 | 1.402 (14) | C14—C15 | 1.523 (15) |
C4—H4 | 0.9500 | C14—H14A | 0.9900 |
C6—C7 | 1.537 (14) | C14—H14B | 0.9900 |
C8—C9 | 1.535 (14) | C15—H15A | 0.9800 |
C8—H8A | 0.9900 | C15—H15B | 0.9800 |
C8—H8B | 0.9900 | C15—H15C | 0.9800 |
C5—N1—C4 | 118.2 (8) | C8—C9—H9B | 109.6 |
C6—N2—C5 | 122.4 (8) | H9A—C9—H9B | 108.1 |
C6—N2—C8 | 118.7 (7) | C11—C10—C9 | 113.5 (9) |
C5—N2—C8 | 118.9 (8) | C11—C10—H10A | 108.9 |
C7—N3—C1 | 123.1 (8) | C9—C10—H10A | 108.9 |
C7—N3—C12 | 116.0 (8) | C11—C10—H10B | 108.9 |
C1—N3—C12 | 120.9 (8) | C9—C10—H10B | 108.9 |
C2—C1—N3 | 122.6 (9) | H10A—C10—H10B | 107.7 |
C2—C1—C5 | 117.5 (9) | C10—C11—H11A | 109.5 |
N3—C1—C5 | 119.7 (8) | C10—C11—H11B | 109.5 |
C1—C2—C3 | 119.2 (9) | H11A—C11—H11B | 109.5 |
C1—C2—H2 | 120.4 | C10—C11—H11C | 109.5 |
C3—C2—H2 | 120.4 | H11A—C11—H11C | 109.5 |
C2—C3—C4 | 119.5 (9) | H11B—C11—H11C | 109.5 |
C2—C3—Br1 | 120.6 (7) | N3—C12—C13 | 111.1 (8) |
C4—C3—Br1 | 119.5 (7) | N3—C12—H12A | 109.4 |
N1—C4—C3 | 121.3 (9) | C13—C12—H12A | 109.4 |
N1—C4—H4 | 119.3 | N3—C12—H12B | 109.4 |
C3—C4—H4 | 119.3 | C13—C12—H12B | 109.4 |
N1—C5—C1 | 124.0 (8) | H12A—C12—H12B | 108.0 |
N1—C5—N2 | 116.3 (8) | C14—C13—C12 | 112.7 (8) |
C1—C5—N2 | 119.7 (8) | C14—C13—H13A | 109.0 |
O1—C6—N2 | 122.8 (9) | C12—C13—H13A | 109.0 |
O1—C6—C7 | 119.4 (8) | C14—C13—H13B | 109.0 |
N2—C6—C7 | 117.8 (8) | C12—C13—H13B | 109.0 |
O2—C7—N3 | 124.0 (9) | H13A—C13—H13B | 107.8 |
O2—C7—C6 | 118.9 (8) | C13—C14—C15 | 113.4 (9) |
N3—C7—C6 | 117.0 (8) | C13—C14—H14A | 108.9 |
N2—C8—C9 | 111.6 (8) | C15—C14—H14A | 108.9 |
N2—C8—H8A | 109.3 | C13—C14—H14B | 108.9 |
C9—C8—H8A | 109.3 | C15—C14—H14B | 108.9 |
N2—C8—H8B | 109.3 | H14A—C14—H14B | 107.7 |
C9—C8—H8B | 109.3 | C14—C15—H15A | 109.5 |
H8A—C8—H8B | 108.0 | C14—C15—H15B | 109.5 |
C10—C9—C8 | 110.3 (8) | H15A—C15—H15B | 109.5 |
C10—C9—H9A | 109.6 | C14—C15—H15C | 109.5 |
C8—C9—H9A | 109.6 | H15A—C15—H15C | 109.5 |
C10—C9—H9B | 109.6 | H15B—C15—H15C | 109.5 |
C7—N3—C1—C2 | −177.7 (9) | C5—N2—C6—O1 | −174.9 (9) |
C12—N3—C1—C2 | 1.5 (14) | C8—N2—C6—O1 | 4.6 (14) |
C7—N3—C1—C5 | 6.0 (14) | C5—N2—C6—C7 | 4.5 (13) |
C12—N3—C1—C5 | −174.8 (9) | C8—N2—C6—C7 | −176.1 (8) |
N3—C1—C2—C3 | 179.3 (9) | C1—N3—C7—O2 | 178.2 (9) |
C5—C1—C2—C3 | −4.3 (14) | C12—N3—C7—O2 | −1.1 (14) |
C1—C2—C3—C4 | 5.2 (15) | C1—N3—C7—C6 | −5.1 (13) |
C1—C2—C3—Br1 | 178.5 (7) | C12—N3—C7—C6 | 175.7 (8) |
C5—N1—C4—C3 | 3.2 (13) | O1—C6—C7—O2 | −3.9 (14) |
C2—C3—C4—N1 | −4.7 (14) | N2—C6—C7—O2 | 176.8 (9) |
Br1—C3—C4—N1 | −178.1 (7) | O1—C6—C7—N3 | 179.2 (9) |
C4—N1—C5—C1 | −2.4 (14) | N2—C6—C7—N3 | −0.1 (12) |
C4—N1—C5—N2 | 178.5 (8) | C6—N2—C8—C9 | −89.8 (10) |
C2—C1—C5—N1 | 3.0 (15) | C5—N2—C8—C9 | 89.6 (10) |
N3—C1—C5—N1 | 179.5 (9) | N2—C8—C9—C10 | −178.6 (8) |
C2—C1—C5—N2 | −177.9 (9) | C8—C9—C10—C11 | −177.1 (9) |
N3—C1—C5—N2 | −1.4 (14) | C7—N3—C12—C13 | −93.8 (10) |
C6—N2—C5—N1 | 175.3 (8) | C1—N3—C12—C13 | 87.0 (10) |
C8—N2—C5—N1 | −4.1 (12) | N3—C12—C13—C14 | −179.1 (8) |
C6—N2—C5—C1 | −3.8 (13) | C12—C13—C14—C15 | −175.0 (8) |
C8—N2—C5—C1 | 176.8 (9) |
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H2···O1i | 0.95 | 2.33 | 3.253 (12) | 164 |
C12—H12A···O1i | 0.99 | 2.55 | 3.447 (11) | 150 |
Symmetry code: (i) −x+1/2, y−1/2, z−1/2. |
Acknowledgements
JTM thanks Tulane University for support of the Tulane Crystallography Laboratory.
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