6,8-Dibromo­quinoline

The title mol­ecule, C₉H₅Br₂N, is almost planar, with an r.m.s. deviation of 0.027 Å. The dihedral angle between the aromatic rings is 1.5 (3)°. In the crystal, π–π stacking inter­actions are present between the pyridine and benzene rings of adjacent mol­ecules [centroid–centroid distances = 3.634 (4) Å], and short Br...Br contacts [3.4443 (13) Å] occur.

Key indicators

• Single-crystal X-ray study
• T = 297 K
• Mean [sigma](C-C) = 0.010 Å
• R factor = 0.045
• wR factor = 0.141
• Data-to-parameter ratio = 14.7

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT029_ALERT_3_B _diffrn_measured_fraction_theta_full Low .......       0.95

Alert level C
REFLT03_ALERT_3_C  Reflection count < 95% complete
           From the CIF: _diffrn_reflns_theta_max           70.45
           From the CIF: _diffrn_reflns_theta_full          70.45
           From the CIF: _reflns_number_total               1598
           TEST2: Reflns within _diffrn_reflns_theta_max
           Count of symmetry unique reflns         1689
           Completeness (_total/calc)             94.61%
PLAT022_ALERT_3_C Ratio Unique / Expected Reflections too Low ....       0.95
PLAT341_ALERT_3_C Low Bond Precision on  C-C Bonds (x 1000) Ang ..         10
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600         67
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600         20

Alert level G
PLAT431_ALERT_2_G Short Inter HL..A Contact  Br1    ..  Br1     ..       3.44 Ang.

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
   5 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   5 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The quinoline skeleton is often used for designing of many synthetic compounds with diverse pharmacological and medicinal properties. Quinolines and their derivatives have shown to display a wide spectrum of biological activities such as antibacterial (Metwally et al., 2006), antimycobacterial (Vinsova et al., 2008; Vangapandu et al., 2004), antineoplastic (Zhao et al., 2005; Sissi & Palumbo, 2003; Musiol et al., 2007; Zhu et al., 2007), antiparasitical (Muscia et al., 2006; Blackie et al., 2007; Gómez et al., 2008; Gómez-Barrio et al., 2006; Kouznetsov et al., 2005, 2007), and anti-inflammatory behavior (Chen et al., 2006; Abadi et al., 2005; Ökten et al., 2010). Quinoline also constitutes a key structural component of numerous compounds with pharmacological activity, dyestuffs, materials with metal-halogen exchange, and agrochemical (Lindley, 1984) and couplings (Vladímir et al., 2005). Bromoquinolines have been of interest for chemists as precursors for heterocyclic compounds due to important scaffolds in medicinal chemistry. It was developed a convenient synthetic methodology for 6,8-disubstituted quinoline derivatives and the values of 6,8-dibromoquinoline as precursors to the corresponding disubstituted quinolines were presented. New disubstituted quinoline derivatives were synthesized via substition reaction by using 6,8-DiBrQ, converted to further substituted quinoline. That may serve for the synthesis of natural bioactive quinolines derivatives because there are many biological active 6 and 8- functionalized quinolines such as quinine, pentaquine, and plasmoquine (Şahin et al., 2008).

The molecular structure of the title compound (I) is shown in Fig. 1 with their respective labels. Bond lengths and angles in (I) are within normal ranges. In this structure, the quinoline motif (N1/C1–C9) is essentially planar with maxium deviations of 0.029 (7) Å for C3 and 0.031 (9) Å for C8. The Br1—C2—C3—C4 and Br2—C4—C5—C6 torsion angles are -179.0 (5) and 178.7 (5)°, respectively.

The crystal structure of (I) is stabilized by π–π stacking interactions, along the a axis, between N1/C1/C6–C9 (centroid Cg1) and C1–C6 (centroid Cg2) rings, with a Cg1···Cg2 distance of 3.634 (4) Å, (Fig. 2).

Related literature

For the biological and pharmacological activities of quinolines and their derivatives, see: Abadi et al. (2005); Blackie et al. (2007); Chen et al. (2006); Gómez et al. (2008); Gómez-Barrio et al. (2006); Kouznetsov et al. (2005, 2007); Lindley (1984); Metwally et al. (2006); Muscia et al. (2006); Musiol et al. (2007); Sissi & Palumbo (2003); Vangapandu et al. (2004); Vinsova et al. (2008); Vladímir et al. (2005); Zhao et al. (2005); Zhu et al. (2007); Şahin et al. (2008). For the synthesis, see: Ökten et al. (2010).

S2. Experimental

6,8-DiBromo-1,2,3,4-tetrahydroquinoline was synthesized in proper literature (Ökten et al., 2010). Then, DDQ (2 g, 6.88 mmol) was dissolved in freshly distilled and dried bezene (10 ml) under an argon atmosphere. To a solution of 6,8-diBrTHQ (1 g, 3.44 mmol) in benzene (30 ml) was added the solution of DDQ. The mixture was refluxed at 353 K for 36 h. Upon cooling, the dark green solidified mixture was filtered and the solvent was removed in vacuo. The residue was filtered from a short silica column (1/9, EtOAc/hexane, R_f= 0.4). Recrystallization of the product from hexane–chloroform gave 6,8-diBrQ in a yield of 88% (868 mg) as colourless plates, m.p. 372–373 K. ¹H NMR (CDCl₃, 400 MHz) d 9.04 (dd, J₂₃= 4.2 Hz, J₂₄= 1.6 Hz, 1H, H₂), 8.16 (d, J₅₇= 2.4 Hz, 1H, H₇), 8.09 (dd, J₄₃= 8.3 Hz, J₂₄= 1.6 Hz, 1H, H₄), 7.96 (d, J₅₇= 2.4 Hz, 1H, H₅), 7.49 (dd, J₃₂= 4.2 Hz, J₃₄= 8.3 Hz, 1H, H₃); ¹³C NMR (100 MHz, CDCl₃) d 151.5, 144.1135.9, 135.7, 130.1, 129.7, 125.9, 122.7, 119.9; IR (KBr, cm^-1) vmax 3026, 1638, 1617, 1587, 1545, 1467, 1443, 1347, 1306, 1183, 1084, 1030, 962, 857, 809, 779, 677, 593, 543, 501. GC–MS m/z 289 (5, M⁺), 288 (50), 287 (10), 286 (98), 285 (10), 284 (42), 207 (30), 205 (31), 129 (5), 127 (10), 126 (100), 125 (14), 103 (15), 102 (14), 99 (37), 98 (33), 97 (20), 75 (19), 74 (22), 73 (42), 50 (18), 49 (52), 48 (14), 37 (7), 36 (7). Anal. Calcd for C₉H₅NBr₂ (286.95): C 37.67, H 1.76%. Found: C 37.78, H 1.82%.

S3. Refinement

H atoms were included in geometric positions with C—H = 0.93 Å and refined by using a riding model [U_iso(H) = 1.2U_eq(C)].

Computing details

Data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO (Oxford Diffraction, 2009); data reduction: CrysAlis PRO (Oxford Diffraction, 2009); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1999); software used to prepare material for publication: WinGX (Farrugia, 1997) and PLATON (Spek, 2009).

Figures

	Fig. 1. The title molecule with displacement ellipsoids for non-H atoms drawn at the 50% probability level.
	Fig. 2. View of the packing of (I) down the a axis.

6,8-Dibromoquinoline

Crystal data

C9H5Br2N	F(000) = 544
Mr = 286.94	Dx = 2.140 Mg m^−3
Monoclinic, P21/c	Cu Kα radiation, λ = 1.54184 Å
Hall symbol: -P 2ybc	Cell parameters from 1247 reflections
a = 7.3436 (12) Å	θ = 3.6–70.3°
b = 9.8961 (15) Å	µ = 11.04 mm^−1
c = 13.0108 (18) Å	T = 297 K
β = 109.589 (17)°	Plate, colourless
V = 890.8 (3) Å^3	0.12 × 0.09 × 0.02 mm
Z = 4

Data collection

Oxford Diffraction Xcalibur diffractometer with a Ruby Gemini CCD detector	1598 independent reflections
Radiation source: Enhance (Cu) X-ray Source	1075 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.000
ω scans	θmax = 70.5°, θmin = 5.8°
Absorption correction: part of the refinement model (ΔF) [XABS2 (Parkin et al., 1995); cubic fit to sin(θ)/λ - 24 parameters]	h = −8→8
Tmin = 0.052, Tmax = 0.080	k = 0→11
1598 measured reflections	l = 0→15

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.141	H-atom parameters constrained
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0642P)^2] where P = (Fo^2 + 2Fc^2)/3
1598 reflections	(Δ/σ)max < 0.001
109 parameters	Δρmax = 0.68 e Å^−3
0 restraints	Δρmin = −0.56 e Å^−3

Special details

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

Refinement. Refinement on F² for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The observed criterion of F² > σ(F²) is used only for calculating -R-factor-obs 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 (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.93324 (12)	0.16374 (8)	0.01474 (6)	0.0736 (3)
Br2	0.54665 (13)	0.49672 (10)	−0.34185 (6)	0.0832 (4)
N1	0.8781 (8)	0.4050 (6)	0.1454 (4)	0.0641 (19)
C1	0.8034 (8)	0.4311 (7)	0.0368 (5)	0.055 (2)
C2	0.8120 (8)	0.3287 (6)	−0.0384 (5)	0.0528 (19)
C3	0.7418 (9)	0.3499 (7)	−0.1488 (5)	0.0595 (19)
C4	0.6545 (9)	0.4739 (7)	−0.1875 (5)	0.0550 (19)
C5	0.6420 (9)	0.5744 (7)	−0.1208 (5)	0.059 (2)
C6	0.7184 (9)	0.5558 (7)	−0.0071 (5)	0.058 (2)
C7	0.7125 (10)	0.6584 (8)	0.0673 (6)	0.067 (3)
C8	0.7919 (11)	0.6338 (9)	0.1768 (6)	0.075 (3)
C9	0.8687 (11)	0.5055 (9)	0.2115 (6)	0.075 (3)
H3	0.75210	0.28330	−0.19700	0.0710*
H5	0.58330	0.65570	−0.14950	0.0710*
H7	0.65560	0.74140	0.04220	0.0800*
H8	0.79470	0.70100	0.22730	0.0900*
H9	0.91680	0.48940	0.28620	0.0900*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0902 (6)	0.0440 (5)	0.0739 (5)	0.0092 (4)	0.0106 (4)	0.0044 (3)
Br2	0.1024 (7)	0.0722 (7)	0.0649 (5)	0.0056 (5)	0.0146 (4)	0.0115 (4)
N1	0.065 (3)	0.056 (4)	0.068 (3)	−0.007 (3)	0.018 (2)	−0.005 (3)
C1	0.047 (3)	0.040 (4)	0.074 (4)	−0.003 (3)	0.014 (3)	−0.004 (3)
C2	0.052 (3)	0.033 (4)	0.070 (3)	0.001 (3)	0.016 (3)	0.005 (3)
C3	0.057 (3)	0.049 (4)	0.066 (3)	−0.001 (3)	0.012 (3)	−0.001 (3)
C4	0.056 (3)	0.046 (4)	0.061 (3)	−0.001 (3)	0.017 (3)	0.009 (3)
C5	0.055 (3)	0.043 (4)	0.076 (4)	0.004 (3)	0.019 (3)	0.002 (3)
C6	0.050 (3)	0.047 (4)	0.078 (4)	0.001 (3)	0.024 (3)	−0.004 (3)
C7	0.067 (4)	0.052 (5)	0.084 (4)	0.005 (3)	0.030 (3)	−0.007 (4)
C8	0.079 (5)	0.068 (6)	0.084 (5)	−0.004 (4)	0.036 (4)	−0.013 (4)
C9	0.077 (5)	0.078 (6)	0.070 (4)	−0.016 (4)	0.025 (3)	−0.015 (4)

Geometric parameters (Å, º)

Br1—C2	1.877 (6)	C5—C6	1.407 (9)
Br2—C4	1.909 (6)	C6—C7	1.414 (10)
N1—C1	1.358 (8)	C7—C8	1.368 (10)
N1—C9	1.332 (10)	C8—C9	1.401 (12)
C1—C2	1.425 (9)	C3—H3	0.9300
C1—C6	1.414 (10)	C5—H5	0.9300
C2—C3	1.370 (9)	C7—H7	0.9300
C3—C4	1.398 (10)	C8—H8	0.9300
C4—C5	1.343 (9)	C9—H9	0.9300
Br1···Br1^i	3.4443 (13)
C1—N1—C9	116.1 (6)	C5—C6—C7	122.2 (6)
N1—C1—C2	118.9 (6)	C6—C7—C8	119.0 (7)
N1—C1—C6	123.8 (6)	C7—C8—C9	118.8 (7)
C2—C1—C6	117.3 (6)	N1—C9—C8	124.8 (7)
Br1—C2—C1	119.4 (5)	C2—C3—H3	121.00
Br1—C2—C3	119.0 (5)	C4—C3—H3	121.00
C1—C2—C3	121.6 (6)	C4—C5—H5	120.00
C2—C3—C4	118.6 (6)	C6—C5—H5	120.00
Br2—C4—C3	117.5 (5)	C6—C7—H7	120.00
Br2—C4—C5	119.9 (5)	C8—C7—H7	120.00
C3—C4—C5	122.7 (6)	C7—C8—H8	121.00
C4—C5—C6	119.5 (6)	C9—C8—H8	121.00
C1—C6—C5	120.3 (6)	N1—C9—H9	118.00
C1—C6—C7	117.5 (6)	C8—C9—H9	118.00
C9—N1—C1—C2	178.9 (6)	C1—C2—C3—C4	−2.1 (10)
C9—N1—C1—C6	−0.3 (10)	C2—C3—C4—C5	2.1 (11)
C1—N1—C9—C8	−1.3 (12)	C2—C3—C4—Br2	−176.9 (5)
N1—C1—C2—Br1	−2.1 (8)	Br2—C4—C5—C6	178.7 (5)
N1—C1—C2—C3	−179.0 (6)	C3—C4—C5—C6	−0.3 (11)
C6—C1—C2—C3	0.3 (9)	C4—C5—C6—C7	179.0 (7)
N1—C1—C6—C5	−179.2 (6)	C4—C5—C6—C1	−1.6 (10)
C6—C1—C2—Br1	177.2 (5)	C1—C6—C7—C8	1.4 (11)
C2—C1—C6—C5	1.6 (10)	C5—C6—C7—C8	−179.2 (7)
C2—C1—C6—C7	−179.0 (6)	C6—C7—C8—C9	−2.8 (12)
N1—C1—C6—C7	0.2 (10)	C7—C8—C9—N1	2.9 (13)
Br1—C2—C3—C4	−179.0 (5)

Symmetry code: (i) −x+2, −y, −z.