organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2414-3146

6-Bromo-2-methyl-1H-imidazo[4,5-b]pyridine

aLaboratoire de Chimie de la Matière Condensée, Faculté des Sciences et Techniques, Université Sidi Mohamed Ben Abdallah, Fez, Morocco, bLaboratoire de Chimie Organique Appliquée, Université Sidi Mohamed Ben Abdallah, Faculté des Sciences et Techniques, Route d'Iimmouzzer, BP 2202, Fez, Morocco, cDepartment of Chemistry, Tulane University, New Orleans, LA 70118, USA, dLaboratoire de Chimie Organique Hétérocyclique, Pôle de Compétences Pharmacochimie, Mohammed V University in Rabat, BP 1014, Avenue Ibn Batouta, Rabat, Morocco, and eDépartement de Chimie, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, 80000 Agadir, Morocco
*Correspondence e-mail: youssef_kandri_rodi@yahoo.fr

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 6 May 2016; accepted 8 May 2016; online 20 May 2016)

The title mol­ecule, C7H6BrN3, crystallizes with two mol­ecules, A and B, in the asymmetric unit, with all non-hydrogen atoms lying on a crystallographic mirror plane. In the crystal, the mol­ecules are linked into [100] chains of alternating A and B mol­ecules by complementary N—H⋯N and C—H⋯N hydrogen bonds. The chains are associated through offset aromatic ππ stacking [shortest centroid–centroid separation = 3.6215 (9) Å] along the b axis.

3D view (loading...)
[Scheme 3D1]
Chemical scheme
[Scheme 1]

Structure description

Heterocyclic ring systems having the imidazo[4,5-b]pyridine nucleus can be considered as structural analogues of purines and have shown diverse biological activities depending on the substituents of the heterocyclic ring. Their activities include anti-cancer (Lukasik et al., 2012[Lukasik, P. M., Elabar, S., Lam, F., Shao, H., Liu, X., Abbas, A. Y. & Wang, S. (2012). Eur. J. Med. Chem. 57, 311-322.]), anti­viral (Cristalli, et al., 1995[Cristalli, G., Vittori, S., Eleuteri, A., Volpini, R., Camaioni, E., Lupidi, G., Mahmood, N., Bevilacqua, F. & Palù, G. (1995). J. Med. Chem. 38, 4019-4025.]) and anti­mitotic (Aridoss et al., 2006[Aridoss, G., Balasubramanian, S., Parthiban, P. & Kabilan, S. (2006). Eur. J. Med. Chem. 41, 268-275.]) actions.

In this study, we have reacted 3-acetyl-4-hy­droxy-6-methyl-3H-pyran-2-one (de­hydro­acetic acid) with 5-bromo­pyridine-2,3-di­amine to furnish the title compound 6-bromo-2-methyl-1H-imidazo[4,5-b]pyridine·The asymmetric unit (Fig. 1[link]) consists of two mol­ecules, each lying on a crystallographic mirror plane.

[Figure 1]
Figure 1
The asymmetric unit with 50% probability ellipsoids. Hydrogen bonds are shown as dashed lines.

In the crystal, complementary pairs of N2—H2⋯N4 and C3—H3⋯N5 as well as N6—H6⋯N1i and C10—H10⋯N3i [symmetry code: (i) x − 1, y, z] hydrogen bonds (Table 1[link]) form chains running parallel to the a axis. These ribbons form stacks in the b-axis direction which are associated through offset π-stacking with an average inter­planar spacing of 3.236 (1) Å (Fig. 2[link]).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N2—H2⋯N4 0.91 1.94 2.845 (4) 172
C3—H3⋯N5 0.95 2.43 3.286 (4) 150
N6—H6⋯N1i 0.91 1.97 2.876 (4) 180
C10—H10⋯N3i 0.95 2.48 3.312 (4) 146
Symmetry code: (i) x-1, y, z.
[Figure 2]
Figure 2
Packing showing portions of two ribbons with the N—H⋯N inter­actions shown as blue dotted lines, the C—H⋯N inter­actions as black dotted lines and the offset π-stacking as purple dotted lines.

Synthesis and crystallization

De­hydro­acetic acid (3-acetyl-4-hy­droxy-6-methyl-3H-pyran-2-one) (0.27 g, 1.6 mmol) was added to a solution of 5-bromo­pyridine-2,3-di­amine (0.3 g, 1.6 mmol) in ethanol (15 ml). The mixture was heated for 24 h. After the completion of reaction (as monitored by TLC), the mixture was filtered. The compound was recrystallized from ethanol–water (1:1) solution to afford colourless plates (yield = 68%).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link].

Table 2
Experimental details

Crystal data
Chemical formula C7H6BrN3
Mr 212.06
Crystal system, space group Monoclinic, P21/m
Temperature (K) 150
a, b, c (Å) 11.0395 (12), 6.4734 (7), 11.1397 (12)
β (°) 98.889 (1)
V3) 786.52 (15)
Z 4
Radiation type Mo Kα
μ (mm−1) 5.16
Crystal size (mm) 0.18 × 0.17 × 0.06
 
Data collection
Diffractometer Bruker SMART APEX CCD
Absorption correction Numerical (SADABS; Bruker, 2016[Bruker (2016). APEX3, SADABS and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.])
Tmin, Tmax 0.39, 0.73
No. of measured, independent and observed [I > 2σ(I)] reflections 14675, 2117, 1578
Rint 0.049
(sin θ/λ)max−1) 0.667
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.035, 0.090, 0.99
No. of reflections 2117
No. of parameters 135
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.71, −0.37
Computer programs: APEX3 and SAINT (Bruker, 2016[Bruker (2016). APEX3, SADABS and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXT (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL2014 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]), PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Structural data


Experimental top

Dehydroacetic acid (3-acetyl-4-hydroxy-6-methyl-3H-pyran-2-one) (0.27 g, 1.6 mmol) was added to a solution of 5-bromopyridine-2,3-diamine (0.3 g, 1.6 mmol) in ethanol (15 ml). The mixture was heated for 24 h. After the completion of reaction (as monitored by TLC), the mixture was filtered. The compound was recrystallized from ethanol–water (1:1) solution to afford colourless plates (yield = 68%).

Refinement top

Crystal data, data collection and structure refinement details are summarized in Table 2.

Structure description top

Heterocyclic ring systems having the imidazo[4,5-b]pyridine nucleus can be considered as structural analogues of purines and have shown diverse biological activities depending on the substituents of the heterocyclic ring. Their activities include anti-cancer (Lukasik et al., 2012), antiviral (Cristalli, et al., 1995) and antimitotic (Aridoss et al., 2006) actions.

In this study, we have reacted 3-acetyl-4-hydroxy-6-methyl-3H-pyran-2-one (dehydroacetic acid) with 5-bromopyridine-2,3-diamine to furnish the title compound 6-bromo-2-methyl-1H-imidazo[4,5-b]pyridine.The asymmetric unit (Fig. 1) consists of two molecules, each lying on a crystallographic mirror plane.

In the crystal, complementary pairs of N2—H2···N4 and C3—H3···N5 as well as N6—H6···N1i and C10—H10···N3i [symmetry code: (i) x - 1, y, z] hydrogen bonds (Table 1) form chains running parallel to the a axis. These ribbons form stacks in the b-axis direction which are associated through offset π-stacking with an average interplanar spacing of 3.236 (1) Å (Fig. 2).

Computing details top

Data collection: APEX3 (Bruker, 2016); cell refinement: 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: PLATON (Spek, 2009); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. The asymmetric unit with 50% probability ellipsoids. Hydrogen bonds are shown as dashed lines.
[Figure 2] Fig. 2. Packing showing portions of two ribbons with the N—H···N interactions shown as blue dotted lines, the C—H···N interactions as black dotted lines and the offset π-stacking as purple dotted lines.
6-Bromo-2-methyl-1H-imidazo[4,5-b]pyridine top
Crystal data top
C7H6BrN3F(000) = 416
Mr = 212.06Dx = 1.791 Mg m3
Monoclinic, P21/mMo Kα radiation, λ = 0.71073 Å
a = 11.0395 (12) ÅCell parameters from 3918 reflections
b = 6.4734 (7) Åθ = 2.8–26.6°
c = 11.1397 (12) ŵ = 5.16 mm1
β = 98.889 (1)°T = 150 K
V = 786.52 (15) Å3Plate, colourless
Z = 40.18 × 0.17 × 0.06 mm
Data collection top
Bruker SMART APEX CCD
diffractometer
2117 independent reflections
Radiation source: fine-focus sealed tube1578 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.049
Detector resolution: 8.3333 pixels mm-1θmax = 28.3°, θmin = 1.9°
φ and ω scansh = 1414
Absorption correction: numerical
(SADABS; Bruker, 2016)
k = 88
Tmin = 0.39, Tmax = 0.73l = 1414
14675 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.035Hydrogen site location: mixed
wR(F2) = 0.090H-atom parameters constrained
S = 0.99 w = 1/[σ2(Fo2) + (0.0521P)2]
where P = (Fo2 + 2Fc2)/3
2117 reflections(Δ/σ)max = 0.001
135 parametersΔρmax = 0.71 e Å3
0 restraintsΔρmin = 0.37 e Å3
Crystal data top
C7H6BrN3V = 786.52 (15) Å3
Mr = 212.06Z = 4
Monoclinic, P21/mMo Kα radiation
a = 11.0395 (12) ŵ = 5.16 mm1
b = 6.4734 (7) ÅT = 150 K
c = 11.1397 (12) Å0.18 × 0.17 × 0.06 mm
β = 98.889 (1)°
Data collection top
Bruker SMART APEX CCD
diffractometer
2117 independent reflections
Absorption correction: numerical
(SADABS; Bruker, 2016)
1578 reflections with I > 2σ(I)
Tmin = 0.39, Tmax = 0.73Rint = 0.049
14675 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0350 restraints
wR(F2) = 0.090H-atom parameters constrained
S = 0.99Δρmax = 0.71 e Å3
2117 reflectionsΔρmin = 0.37 e Å3
135 parameters
Special details top

Experimental. The diffraction data were obtained from 3 sets of 400 frames, each of width 0.5° in ω, colllected at φ = 0.00, 90.00 and 180.00° and 2 sets of 800 frames, each of width 0.45° in φ, collected at ω = –30.00 and 210.00°. The scan time was 25 sec/frame.

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 - 0.98 Å) while those attached to nitrogen were placed in locations derived from a difference map and their coordinates adjusted to give N—H = 0.91 %A. All were included as riding contributions with isotropic displacement parameters 1.2 - 1.5 times those of the attached atoms.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Br10.64714 (4)0.25000.95946 (3)0.05475 (17)
N10.8413 (2)0.25000.6732 (2)0.0256 (6)
N20.5647 (2)0.25000.4725 (2)0.0244 (6)
H20.48250.25000.44580.037*
N30.7651 (2)0.25000.4578 (2)0.0258 (6)
C10.6526 (3)0.25000.3988 (3)0.0250 (7)
C20.6247 (3)0.25000.5894 (3)0.0236 (7)
C30.5883 (3)0.25000.7027 (3)0.0273 (7)
H30.50460.25000.71370.033*
C40.6838 (3)0.25000.7984 (3)0.0301 (7)
C50.8062 (3)0.25000.7818 (3)0.0309 (8)
H50.86760.25000.85170.037*
C60.7515 (3)0.25000.5782 (3)0.0223 (6)
C70.6185 (3)0.25000.2642 (3)0.0316 (8)
H7A0.68690.30420.22710.047*0.5
H7B0.54610.33720.24110.047*0.5
H7C0.60010.10850.23580.047*0.5
Br20.02840 (4)0.25000.11797 (3)0.04217 (15)
N40.3046 (2)0.25000.4123 (2)0.0254 (6)
N50.2886 (2)0.25000.6267 (2)0.0263 (6)
N60.0824 (2)0.25000.6055 (2)0.0270 (6)
H60.00620.25000.62720.040*
C80.1909 (3)0.25000.6830 (3)0.0281 (7)
C90.1110 (3)0.25000.4897 (3)0.0240 (7)
C100.0408 (3)0.25000.3754 (3)0.0268 (7)
H100.04630.25000.36270.032*
C110.1099 (3)0.25000.2813 (3)0.0271 (7)
C120.2380 (3)0.25000.3016 (3)0.0253 (7)
H120.27980.25000.23320.030*
C130.2401 (3)0.25000.5052 (3)0.0239 (7)
C140.1952 (3)0.25000.8164 (3)0.0385 (9)
H14A0.17290.38720.84300.058*0.5
H14B0.27830.21550.85590.058*0.5
H14C0.13740.14730.83870.058*0.5
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.0464 (3)0.0974 (4)0.0221 (2)0.0000.01081 (17)0.000
N10.0195 (13)0.0290 (15)0.0279 (14)0.0000.0027 (11)0.000
N20.0184 (13)0.0324 (15)0.0224 (13)0.0000.0034 (10)0.000
N30.0242 (14)0.0291 (15)0.0257 (13)0.0000.0088 (11)0.000
C10.0231 (16)0.0255 (17)0.0279 (17)0.0000.0091 (13)0.000
C20.0205 (16)0.0252 (17)0.0249 (16)0.0000.0031 (13)0.000
C30.0225 (16)0.0320 (19)0.0280 (17)0.0000.0053 (13)0.000
C40.0294 (18)0.039 (2)0.0229 (16)0.0000.0077 (14)0.000
C50.0282 (18)0.034 (2)0.0300 (17)0.0000.0025 (14)0.000
C60.0217 (15)0.0204 (16)0.0260 (15)0.0000.0072 (12)0.000
C70.0313 (18)0.042 (2)0.0211 (16)0.0000.0040 (13)0.000
Br20.0371 (2)0.0574 (3)0.0297 (2)0.0000.00230 (15)0.000
N40.0199 (13)0.0258 (14)0.0317 (15)0.0000.0077 (11)0.000
N50.0211 (14)0.0285 (15)0.0298 (14)0.0000.0054 (11)0.000
N60.0201 (14)0.0311 (16)0.0306 (15)0.0000.0069 (11)0.000
C80.0241 (17)0.0274 (18)0.0334 (18)0.0000.0058 (14)0.000
C90.0193 (15)0.0234 (17)0.0308 (16)0.0000.0080 (13)0.000
C100.0200 (15)0.0236 (17)0.0364 (19)0.0000.0028 (14)0.000
C110.0252 (16)0.0258 (18)0.0294 (17)0.0000.0014 (13)0.000
C120.0249 (16)0.0243 (17)0.0277 (16)0.0000.0070 (13)0.000
C130.0212 (15)0.0230 (17)0.0274 (16)0.0000.0033 (13)0.000
C140.039 (2)0.047 (2)0.0298 (18)0.0000.0057 (16)0.000
Geometric parameters (Å, º) top
Br1—C41.899 (3)Br2—C111.901 (3)
N1—C51.326 (4)N4—C121.335 (4)
N1—C61.333 (4)N4—C131.344 (4)
N2—C11.365 (4)N5—C81.329 (4)
N2—C21.367 (4)N5—C131.376 (4)
N2—H20.9100N6—C81.363 (4)
N3—C11.313 (4)N6—C91.375 (4)
N3—C61.372 (4)N6—H60.9100
C1—C71.488 (4)C8—C141.480 (5)
C2—C31.383 (4)C9—C101.384 (4)
C2—C61.425 (4)C9—C131.409 (4)
C3—C41.378 (5)C10—C111.389 (4)
C3—H30.9500C10—H100.9500
C4—C51.392 (4)C11—C121.397 (4)
C5—H50.9500C12—H120.9500
C7—H7A0.9800C14—H14A0.9800
C7—H7B0.9800C14—H14B0.9800
C7—H7C0.9800C14—H14C0.9800
C5—N1—C6116.0 (3)C12—N4—C13115.4 (3)
C1—N2—C2106.8 (3)C8—N5—C13104.1 (3)
C1—N2—H2124.6C8—N6—C9106.7 (3)
C2—N2—H2128.6C8—N6—H6126.1
C1—N3—C6104.6 (2)C9—N6—H6127.2
N3—C1—N2113.8 (3)N5—C8—N6113.5 (3)
N3—C1—C7125.2 (3)N5—C8—C14124.8 (3)
N2—C1—C7120.9 (3)N6—C8—C14121.6 (3)
N2—C2—C3134.7 (3)N6—C9—C10133.3 (3)
N2—C2—C6104.8 (3)N6—C9—C13105.0 (3)
C3—C2—C6120.5 (3)C10—C9—C13121.7 (3)
C4—C3—C2114.2 (3)C9—C10—C11113.6 (3)
C4—C3—H3122.9C9—C10—H10123.2
C2—C3—H3122.9C11—C10—H10123.2
C3—C4—C5122.7 (3)C10—C11—C12122.5 (3)
C3—C4—Br1118.8 (2)C10—C11—Br2119.3 (2)
C5—C4—Br1118.6 (2)C12—C11—Br2118.2 (2)
N1—C5—C4123.2 (3)N4—C12—C11123.3 (3)
N1—C5—H5118.4N4—C12—H12118.3
C4—C5—H5118.4C11—C12—H12118.3
N1—C6—N3126.6 (3)N4—C13—N5125.8 (3)
N1—C6—C2123.4 (3)N4—C13—C9123.5 (3)
N3—C6—C2110.0 (3)N5—C13—C9110.7 (3)
C1—C7—H7A109.5C8—C14—H14A109.5
C1—C7—H7B109.5C8—C14—H14B109.5
H7A—C7—H7B109.5H14A—C14—H14B109.5
C1—C7—H7C109.5C8—C14—H14C109.5
H7A—C7—H7C109.5H14A—C14—H14C109.5
H7B—C7—H7C109.5H14B—C14—H14C109.5
C6—N3—C1—N20.000 (1)C13—N5—C8—N60.000 (1)
C6—N3—C1—C7180.000 (1)C13—N5—C8—C14180.000 (1)
C2—N2—C1—N30.000 (1)C9—N6—C8—N50.000 (1)
C2—N2—C1—C7180.000 (1)C9—N6—C8—C14180.000 (1)
C1—N2—C2—C3180.000 (1)C8—N6—C9—C10180.000 (1)
C1—N2—C2—C60.000 (1)C8—N6—C9—C130.000 (1)
N2—C2—C3—C4180.000 (1)N6—C9—C10—C11180.000 (1)
C6—C2—C3—C40.000 (1)C13—C9—C10—C110.000 (1)
C2—C3—C4—C50.000 (1)C9—C10—C11—C120.000 (1)
C2—C3—C4—Br1180.000 (1)C9—C10—C11—Br2180.000 (1)
C6—N1—C5—C40.000 (1)C13—N4—C12—C110.000 (1)
C3—C4—C5—N10.000 (1)C10—C11—C12—N40.000 (1)
Br1—C4—C5—N1180.000 (1)Br2—C11—C12—N4180.000 (1)
C5—N1—C6—N3180.000 (1)C12—N4—C13—N5180.000 (1)
C5—N1—C6—C20.000 (1)C12—N4—C13—C90.000 (1)
C1—N3—C6—N1180.000 (1)C8—N5—C13—N4180.000 (1)
C1—N3—C6—C20.000 (1)C8—N5—C13—C90.000 (1)
N2—C2—C6—N1180.000 (1)N6—C9—C13—N4180.000 (1)
C3—C2—C6—N10.000 (1)C10—C9—C13—N40.000 (1)
N2—C2—C6—N30.000 (1)N6—C9—C13—N50.000 (1)
C3—C2—C6—N3180.000 (1)C10—C9—C13—N5180.000 (1)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2···N40.911.942.845 (4)172
C3—H3···N50.952.433.286 (4)150
N6—H6···N1i0.911.972.876 (4)180
C10—H10···N3i0.952.483.312 (4)146
Symmetry code: (i) x1, y, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2···N40.911.942.845 (4)172.0
C3—H3···N50.952.433.286 (4)150
N6—H6···N1i0.911.972.876 (4)180
C10—H10···N3i0.952.483.312 (4)146
Symmetry code: (i) x1, y, z.

Experimental details

Crystal data
Chemical formulaC7H6BrN3
Mr212.06
Crystal system, space groupMonoclinic, P21/m
Temperature (K)150
a, b, c (Å)11.0395 (12), 6.4734 (7), 11.1397 (12)
β (°) 98.889 (1)
V3)786.52 (15)
Z4
Radiation typeMo Kα
µ (mm1)5.16
Crystal size (mm)0.18 × 0.17 × 0.06
Data collection
DiffractometerBruker SMART APEX CCD
Absorption correctionNumerical
(SADABS; Bruker, 2016)
Tmin, Tmax0.39, 0.73
No. of measured, independent and
observed [I > 2σ(I)] reflections
14675, 2117, 1578
Rint0.049
(sin θ/λ)max1)0.667
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.035, 0.090, 0.99
No. of reflections2117
No. of parameters135
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.71, 0.37

Computer programs: APEX3 (Bruker, 2016), SAINT (Bruker, 2016), SHELXT (Sheldrick, 2015a), SHELXL2014 (Sheldrick, 2015b), PLATON (Spek, 2009), publCIF (Westrip, 2010).

 

Acknowledgements

JTM thanks Tulane University for support of the Tulane Crystallography Laboratory.

References

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