Ethyl 3,7-dichloro­quinoline-8-carboxyl­ate

The title compound, C₁₂H₉Cl₂NO₂, was prepared by the esterification of 3,7-dichloro­quinoline-8-carboxylic acid with triethyl phosphite. The crystal structure is stabilized by aromatic π–π stacking between the benzene and the pyridine rings of neighbouring mol­ecules [centroid–centroid distances = 3.716 (2) and 3.642 (2) Å]. In addition, weak inter­molecular C—H...N hydrogen bonds are present in the structure.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.043
• wR factor = 0.117
• Data-to-parameter ratio = 17.7

checkCIF/PLATON results

No syntax errors found



Alert level C
            Value of measurement temperature given =   296.000
            Value of melting point given =     0.000
SHFSU01_ALERT_2_C  Test not performed. _refine_ls_shift/su_max and
            _refine_ls_shift/esd_max not present.
            Absolute value of the parameter shift to su ratio given   0.001
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        C11
PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical .          ?

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

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

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S1. Comment

Quinclorac (3,7-dichloroquinoline-8-carboxylic acid) is one of the most effective herbicides (Nuria et al., 1997; Pornprom et al., 2006; Sunohara & Matsumoto, 2004; Tresch & Grossmann, 2002). Usually, it was prepared via Skraup cyclization from 2-methyl-3- chloroaniline, followed by chlorination and oxidation (Yang et al., 2002). Furthermore, quinolinecarboxylates can chelate to metal atoms, forming the complexes, such as trans-Dimethanolbis(quinoline-8-carboxylato-κ²N,O)- cobalt(II) (Che et al.,2005),catena-Poly[nickel(II)-bis(µ-3,7-dichloroquinoline-8-χarboxylato-κ³N,O:O')] (Zhang et al., 2007), catena-Poly[cobalt(II)-bis (l-3,7-dichloroquinoline-8-carboxylato-κ³N,O:O')] (Li et al., 2008). More recently, we also have reported a Zinc-quinclorac complex (An et al., 2008) and quinclorac (Guo, 2008). But the derivatives of 3,7-dichloroquinoline-8-carboxylic acid have been less reported (Liang et al., 2006). Here we report the crystal structure of the title compound, ethyl 3,7-dichloroquinoline-8-carboxylate (I) (Fig. 1).

In the title compound (I), as shown in Fig. 1, the plane (O1—C10—O2—C11) is nearly vertical to the quinoline ring, in which the dihedral angel is 86.6 (1). The quinoline unit is essentially planar, with a mean deviation of 0.007 (2) Å from the least-squares plane defined by the ten constituent atoms. The molecular packing (Fig. 2) is stabilized by aromatic π—π stackings between the benzene and the pyridine rings of the adjacent molecules. The Cg1···Cg2ⁱⁱ and Cg1···Cg2ⁱⁱⁱ distances are 3.716 (2) and 3.642 (2) Å (Fig. 2; Cg1 and Cg2 are the centroids of the C1/C2/C3/C4/C9/C8 benzene ring and the N1/C7/C6/C5/C9/C8 pyridine ring, respectively, symmetry code as in Fig. 2). The crystal structure is further stabilized by intermolecular C11—H11A···Nⁱ hydrogen bonds (Fig. 2 and Table 1; symmetry code as in Fig. 2).

Related literature

For the use of 3,7-dichloroquinoline-8-carboxylic acid as a herbicide, see: Nuria et al. (1997); Pornprom et al. (2006); Sunohara & Matsumoto (2004); Tresch & Grossmann (2002). For the usual preparative route, see: Yang et al. (2002). For related complexes, see: An et al. (2008); Che et al. (2005); Guo (2008); Li et al. (2008); Turel et al. (2004); Zhang et al. (2007). For 3,7-dichloroquinoline-8-carboxylic acid derivatives, see: Liang et al. (2006);

S2. Experimental

Ethyl 3,7-dichloroquinoline-8-carboxylate was obtained from the reaction of 3,7-dichloroquinoline-8-carboxylic acid with triethyl phosphite in refluxing condition. After recrystallization from ethanol, then it was dissolved the mixture of acetone/petroleum ether (1:4, V/V). The suitable single-crystal for X-ray analysis was obtained by slow evaporation.

S3. Refinement

All H atoms were geometrically positioned and refined using a riding model, with C—H = 0.93 (aromatic), 0.97 (methylene) and 0.96 Å (methyl) H atoms, and with U_iso(H) = 1.2Ueq(C) (aromatic, methylene) and 1.5Ueq(C) (methyl) H atoms.

Computing details

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXS97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2003).

Figures

	Fig. 1. The molecular structure of the title compound, showing displacement ellipsoids drawn at the 30% probability level.
	Fig. 2. π—π stackings and C—H···N interactions (dotted lines) in the title compound. Cg denotes ring centroid. [Symmetry code: (i) -y+5/4, x+1/4, -z+5/4; (ii) -x+1, -y+1, -z+2; (iii)-x+1, -y+1, -z+1.]

Ethyl 3,7-dichloroquinoline-8-carboxylate

Crystal data

C12H9Cl2NO2	Dx = 1.504 Mg m^−3
Mr = 270.10	Melting point: not measured K
Tetragonal, I41/a	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -I_4ad	Cell parameters from 2208 reflections
a = 25.4806 (3) Å	θ = 1.6–26.0°
c = 7.3497 (2) Å	µ = 0.53 mm^−1
V = 4771.87 (15) Å^3	T = 296 K
Z = 16	Needle, colorless
F(000) = 2208	0.10 × 0.08 × 0.06 mm

Data collection

Bruker SMART APEX2 diffractometer	2750 independent reflections
Radiation source: fine-focus sealed tube	1625 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.045
Detector resolution: 10.0 pixels mm^-1	θmax = 27.5°, θmin = 1.6°
ϕ and ω scans	h = −32→33
Absorption correction: multi-scan (SADABS; Bruker, 1999)	k = −33→32
Tmin = 0.950, Tmax = 0.969	l = −9→9
19332 measured reflections

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)] = 0.043	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.117	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0469P)^2 + 1.2301P] where P = (Fo^2 + 2Fc^2)/3
2750 reflections	(Δ/σ)max < 0.001
155 parameters	Δρmax = 0.20 e Å^−3
0 restraints	Δρmin = −0.25 e Å^−3

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cl1	0.65771 (2)	0.53635 (3)	0.60570 (9)	0.0725 (2)
Cl2	0.34654 (3)	0.47136 (3)	0.89519 (10)	0.0809 (3)
O1	0.57642 (7)	0.63042 (6)	0.8389 (2)	0.0714 (5)
O2	0.55721 (6)	0.62556 (5)	0.5418 (2)	0.0560 (4)
N1	0.46789 (7)	0.56227 (7)	0.7898 (3)	0.0535 (5)
C1	0.55677 (8)	0.54727 (8)	0.7053 (3)	0.0479 (5)
C2	0.59627 (8)	0.51296 (8)	0.6642 (3)	0.0511 (5)
C3	0.58827 (9)	0.45826 (9)	0.6676 (3)	0.0582 (6)
H3	0.6157	0.4356	0.6390	0.070*
C4	0.54076 (9)	0.43888 (9)	0.7125 (3)	0.0594 (6)
H4	0.5358	0.4027	0.7144	0.071*
C5	0.44775 (9)	0.45445 (8)	0.8039 (3)	0.0574 (6)
H5	0.4405	0.4187	0.8107	0.069*
C6	0.40972 (9)	0.49023 (9)	0.8394 (3)	0.0555 (6)
C7	0.42156 (9)	0.54368 (9)	0.8316 (3)	0.0577 (6)
H7	0.3949	0.5675	0.8577	0.069*
C8	0.50652 (8)	0.52712 (8)	0.7514 (3)	0.0458 (5)
C9	0.49847 (8)	0.47219 (8)	0.7565 (3)	0.0492 (5)
C10	0.56464 (8)	0.60545 (8)	0.7069 (3)	0.0505 (5)
C11	0.56478 (9)	0.68194 (8)	0.5254 (3)	0.0609 (6)
H11A	0.5999	0.6915	0.5639	0.073*
H11B	0.5398	0.7004	0.6015	0.073*
C12	0.55684 (13)	0.69615 (10)	0.3318 (4)	0.0967 (10)
H12A	0.5809	0.6766	0.2574	0.145*
H12B	0.5630	0.7330	0.3160	0.145*
H12C	0.5215	0.6880	0.2967	0.145*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0602 (4)	0.0814 (5)	0.0760 (5)	0.0005 (3)	0.0113 (3)	−0.0024 (3)
Cl2	0.0661 (4)	0.1000 (5)	0.0765 (5)	−0.0247 (4)	−0.0006 (3)	0.0114 (4)
O1	0.0916 (13)	0.0584 (10)	0.0642 (12)	−0.0132 (9)	−0.0061 (9)	−0.0109 (8)
O2	0.0650 (10)	0.0406 (8)	0.0624 (11)	−0.0065 (7)	−0.0037 (8)	0.0032 (7)
N1	0.0524 (11)	0.0480 (10)	0.0601 (12)	0.0009 (9)	−0.0024 (9)	0.0023 (8)
C1	0.0560 (13)	0.0447 (12)	0.0430 (13)	−0.0014 (10)	−0.0049 (10)	0.0001 (9)
C2	0.0580 (13)	0.0529 (13)	0.0424 (12)	0.0009 (10)	−0.0021 (10)	−0.0015 (10)
C3	0.0704 (16)	0.0530 (14)	0.0511 (14)	0.0128 (11)	−0.0018 (11)	−0.0042 (10)
C4	0.0804 (17)	0.0423 (12)	0.0555 (15)	0.0022 (12)	−0.0030 (12)	−0.0035 (10)
C5	0.0778 (17)	0.0462 (12)	0.0483 (14)	−0.0158 (12)	−0.0057 (11)	0.0036 (10)
C6	0.0584 (14)	0.0637 (15)	0.0445 (13)	−0.0129 (11)	−0.0065 (10)	0.0043 (10)
C7	0.0557 (14)	0.0595 (14)	0.0578 (15)	0.0034 (11)	−0.0035 (11)	0.0037 (11)
C8	0.0567 (13)	0.0418 (12)	0.0389 (12)	0.0007 (10)	−0.0072 (9)	0.0002 (9)
C9	0.0667 (15)	0.0412 (12)	0.0397 (13)	−0.0033 (10)	−0.0077 (10)	0.0014 (9)
C10	0.0456 (12)	0.0497 (13)	0.0562 (15)	−0.0038 (10)	0.0016 (10)	−0.0020 (11)
C11	0.0583 (14)	0.0392 (12)	0.0851 (18)	−0.0080 (10)	0.0071 (12)	0.0011 (11)
C12	0.139 (3)	0.0547 (16)	0.097 (2)	−0.0178 (17)	−0.0243 (19)	0.0215 (15)

Geometric parameters (Å, º)

Cl1—C2	1.729 (2)	C4—H4	0.9300
Cl2—C6	1.730 (2)	C5—C6	1.356 (3)
O1—C10	1.198 (2)	C5—C9	1.413 (3)
O2—C10	1.331 (2)	C5—H5	0.9300
O2—C11	1.454 (2)	C6—C7	1.396 (3)
N1—C7	1.309 (3)	C7—H7	0.9300
N1—C8	1.360 (2)	C8—C9	1.415 (3)
C1—C2	1.367 (3)	C11—C12	1.482 (3)
C1—C8	1.420 (3)	C11—H11A	0.9700
C1—C10	1.496 (3)	C11—H11B	0.9700
C2—C3	1.409 (3)	C12—H12A	0.9600
C3—C4	1.348 (3)	C12—H12B	0.9600
C3—H3	0.9300	C12—H12C	0.9600
C4—C9	1.409 (3)
C10—O2—C11	115.91 (17)	C6—C7—H7	118.1
C7—N1—C8	117.60 (18)	N1—C8—C9	122.72 (19)
C2—C1—C8	119.03 (18)	N1—C8—C1	117.63 (17)
C2—C1—C10	122.47 (18)	C9—C8—C1	119.65 (19)
C8—C1—C10	118.49 (18)	C4—C9—C5	124.3 (2)
C1—C2—C3	121.5 (2)	C4—C9—C8	118.6 (2)
C1—C2—Cl1	120.06 (16)	C5—C9—C8	117.1 (2)
C3—C2—Cl1	118.45 (17)	O1—C10—O2	124.7 (2)
C4—C3—C2	119.8 (2)	O1—C10—C1	124.5 (2)
C4—C3—H3	120.1	O2—C10—C1	110.81 (18)
C2—C3—H3	120.1	O2—C11—C12	107.63 (19)
C3—C4—C9	121.5 (2)	O2—C11—H11A	110.2
C3—C4—H4	119.3	C12—C11—H11A	110.2
C9—C4—H4	119.3	O2—C11—H11B	110.2
C6—C5—C9	119.07 (19)	C12—C11—H11B	110.2
C6—C5—H5	120.5	H11A—C11—H11B	108.5
C9—C5—H5	120.5	C11—C12—H12A	109.5
C5—C6—C7	119.6 (2)	C11—C12—H12B	109.5
C5—C6—Cl2	121.59 (18)	H12A—C12—H12B	109.5
C7—C6—Cl2	118.82 (19)	C11—C12—H12C	109.5
N1—C7—C6	123.9 (2)	H12A—C12—H12C	109.5
N1—C7—H7	118.1	H12B—C12—H12C	109.5

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C11—H11A···N1^i	0.97	2.46	3.299 (3)	145

Symmetry code: (i) −y+5/4, x+1/4, −z+5/4.