6,7-Difluoro-1,2,3,4-tetra­hydro­quin­oxa­line-5,8-dicarbonitrile

Qu, B.-H.; Jia, X.-C.; Li, J.; He, M.-Y.

doi:10.1107/S1600536813003206

organic compounds

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Volume 69| Part 3| March 2013| Page o376

doi:10.1107/S1600536813003206

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6,7-Difluoro-1,2,3,4-tetrahydroquinoxaline-5,8-dicarbonitrile

Bao-Hua Qu,^a Xiao-Chuan Jia,^b Jing Li ^b and Ming-Yang He ^a ^*

^aKey Laboratory of Fine Petrochemical Technology, Changzhou University, Changzhou 213164, People's Republic of China, and ^bTianjin Entry-Exit Inspection and Quarantine Bureau, Tianjin 300457, People's Republic of China
^*Correspondence e-mail: hemingyangjpu@yahoo.com

(Received 29 October 2012; accepted 31 January 2013; online 13 February 2013)

In the title compound, C₁₀H₆F₂N₄, the C_ar—N bonds are slightly shortened with respect to a standard aniline C—N bond [1.3580 (16) and 1.3618 (16) versus 1.39 Å], thus indicating some π–π conjgation with the electron-acceptor CN groups. The molecule, except for two C atom of the ethylene bridge, is nearly planar, the largest deviation of the other non-H atoms from the mean plane being 0.309 (2) Å. The N—C—C—N torsion angle involving the ethylene bridge is 50.23 (18)°. In the crystal, molecules are connected by pairs of N—H⋯N hydrogen bonds into chains along [21-1].

Related literature

For general background to the synthesis and use of tetrafluoroterephthalonitrile and its derivatives, see: Meazza et al. (2007 ). For reference structural data on tetrafluoroterephthalic acid, see: Orthaber et al. (2010 ). For standard bond lengths, see: Allen et al. (1987 ). For hydrogen bonding graph-set descriptors, see: Etter (1990 ).

Experimental

Crystal data

C₁₀H₆F₂N₄
M_r = 220.19
Triclinic, $[P \overline 1]$
a = 5.2173 (9) Å
b = 8.7011 (15) Å
c = 11.1453 (19) Å
α = 75.545 (2)°
β = 81.854 (2)°
γ = 76.427 (2)°
V = 474.40 (14) Å³
Z = 2
Mo Kα radiation
μ = 0.13 mm⁻¹
T = 293 K
0.28 × 0.24 × 0.16 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2003 ) T_min = 0.964, T_max = 0.980
4155 measured reflections
2141 independent reflections
1816 reflections with I > 2σ(I)
R_int = 0.026

Refinement

R[F² > 2σ(F²)] = 0.043
wR(F²) = 0.140
S = 1.06
2141 reflections
145 parameters
H-atom parameters constrained
Δρ_max = 0.29 e Å⁻³
Δρ_min = −0.23 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N3—H3⋯N1ⁱ	0.86	2.29	3.075 (2)	152
N4—H4⋯N2ⁱⁱ	0.86	2.21	3.0358 (19)	160
Symmetry codes: (i) -x+1, -y+1, -z+1; (ii) -x-1, -y, -z+2.

Data collection: APEX2 (Bruker, 2007 ); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL and DIAMOND (Brandenburg, 2005 ); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536813003206/yk2078sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536813003206/yk2078Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536813003206/yk2078Isup3.cml

checkCIF report

Comment top

As important organic intermediates, tetrafluoroterephthalonitrile and its hydrolyzed product tetrafluoroterephthalic acid can be used to prepare pesticide tefluthrin (Meazza et al., 2007; Orthaber et al., 2010). The S_NAr reaction of tetrafluoroterephthalonitrile with ethylenediamine under ultrasound irradiation yields 6,7-difluoro-1,2,3,4-tetrahydroquinoxaline-5,8-dicarbonitrile [C₁₀H₆F₂N₄, compound (I)] as the main product. While the crystal structure of compound (I) was suspiciously unknown. Herein, we report the crystal structure of (I) for comparison and reference purposes.

Compound (I) crystallizes in triclinic P1 space group. A perspective view of the title compound (I) is shown in Fig. 1. The bond lengths and angles are within normal ranges. In the molecule, two nitrile groups are nearly coplanar with the central benzene plane. Within the tetrahydroquinoxaline ring, the torsion angle N3–C10–C9–N4 is -50.23 (18)°. Hydrogen-bonding interactions between the imino groups and cyano groups give rise to cyclic system of two N–H···N bonds between two adjacent molecules with the graph-set motif R₂²(12) (Etter, 1990). Due to the chemical symmetry of the molecule itself, such hydrogen-bonding interactions link the molecules to form a one-dimensional (1-D) tape structure (Fig. 2).

Related literature top

For general background to the synthesis and use of tetrafluoroterephthalonitrile and its derivatives, see: Meazza et al. (2007). For reference structural data on tetrafluoroterephthalic acid, see: Orthaber et al. (2010). For standard bond lengths, see: Allen et al. (1987). For hydrogen bonding graph-set descriptors, see: Etter (1990).

Experimental top

Compound (I) was synthesized by the ultrasound reaction of tetrafluoroterephthalonitrile and ethylenediamine at room temperature in the presence of sulfur and assisted by ultrasound irradiation. The title compound was purified through column chromatography with ethyl acetate/petroleum ether as the eluent. Qualified crystalline samples were obtained through slow evaporation from the EtOH solution of (I).

Computing details top

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 2005); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

	Fig. 1. The molecular structure of the title compound showing the atom labelling scheme. Thermal ellipsoids are drawn at the 30% probability level.
	Fig. 2. 1-D hydrogen-bonding tape of (I) formed by N–H···N interactions. Hydrogen bonds indicated by dashed lines.

6,7-Difluoro-1,2,3,4-tetrahydroquinoxaline-5,8-dicarbonitrile top

Crystal data top

C₁₀H₆F₂N₄	Z = 2
M_r = 220.19	F(000) = 224
Triclinic, P1	D_x = 1.541 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 5.2173 (9) Å	Cell parameters from 2503 reflections
b = 8.7011 (15) Å	θ = 2.5–27.6°
c = 11.1453 (19) Å	µ = 0.13 mm⁻¹
α = 75.545 (2)°	T = 293 K
β = 81.854 (2)°	Block, colorless
γ = 76.427 (2)°	0.28 × 0.24 × 0.16 mm
V = 474.40 (14) Å³

Data collection top

Bruker APEXII CCD diffractometer	2141 independent reflections
Radiation source: fine-focus sealed tube	1816 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.026
ϕ and ω scans	θ_max = 27.6°, θ_min = 1.9°
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	h = −6→6
T_min = 0.964, T_max = 0.980	k = −11→11
4155 measured reflections	l = −14→13

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.043	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.140	H-atom parameters constrained
S = 1.06	w = 1/[σ²(F_o²) + (0.0825P)² + 0.0701P] where P = (F_o² + 2F_c²)/3
2141 reflections	(Δ/σ)_max < 0.001
145 parameters	Δρ_max = 0.29 e Å⁻³
0 restraints	Δρ_min = −0.23 e Å⁻³

Crystal data top

C₁₀H₆F₂N₄	γ = 76.427 (2)°
M_r = 220.19	V = 474.40 (14) Å³
Triclinic, P1	Z = 2
a = 5.2173 (9) Å	Mo Kα radiation
b = 8.7011 (15) Å	µ = 0.13 mm⁻¹
c = 11.1453 (19) Å	T = 293 K
α = 75.545 (2)°	0.28 × 0.24 × 0.16 mm
β = 81.854 (2)°

Data collection top

Bruker APEXII CCD diffractometer	2141 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	1816 reflections with I > 2σ(I)
T_min = 0.964, T_max = 0.980	R_int = 0.026
4155 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.043	0 restraints
wR(F²) = 0.140	H-atom parameters constrained
S = 1.06	Δρ_max = 0.29 e Å⁻³
2141 reflections	Δρ_min = −0.23 e Å⁻³
145 parameters

Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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 (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.5584 (3)	0.24423 (15)	0.57193 (12)	0.0414 (3)
C2	−0.1573 (3)	−0.09578 (15)	0.89446 (12)	0.0403 (3)
C3	0.3758 (2)	0.16100 (14)	0.65684 (11)	0.0359 (3)
C4	0.4178 (2)	−0.00938 (14)	0.67660 (11)	0.0382 (3)
C5	0.2446 (3)	−0.09029 (14)	0.75315 (12)	0.0389 (3)
C6	0.0223 (2)	−0.00551 (14)	0.81451 (11)	0.0359 (3)
C7	−0.0247 (2)	0.16328 (14)	0.79859 (11)	0.0348 (3)
C8	0.1573 (2)	0.24965 (14)	0.71567 (11)	0.0355 (3)
C9	−0.2521 (3)	0.41626 (17)	0.85819 (15)	0.0548 (4)
H9A	−0.1510	0.4206	0.9235	0.066*
H9B	−0.4347	0.4681	0.8760	0.066*
C10	−0.1447 (3)	0.50503 (16)	0.73570 (16)	0.0539 (4)
H10A	−0.2651	0.5195	0.6731	0.065*
H10B	−0.1288	0.6115	0.7421	0.065*
F1	0.63601 (16)	−0.08862 (10)	0.61981 (8)	0.0525 (3)
F2	0.28294 (18)	−0.25305 (9)	0.77522 (9)	0.0548 (3)
N1	0.6992 (3)	0.31503 (17)	0.50478 (13)	0.0574 (4)
N2	−0.3029 (3)	−0.16595 (16)	0.95803 (12)	0.0560 (3)
N3	0.1134 (2)	0.41386 (13)	0.69902 (12)	0.0481 (3)
H3	0.2066	0.4607	0.6368	0.058*
N4	−0.2375 (2)	0.24862 (13)	0.85611 (11)	0.0463 (3)
H4	−0.3500	0.2005	0.9065	0.056*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0426 (7)	0.0361 (6)	0.0434 (7)	−0.0099 (5)	0.0025 (5)	−0.0070 (5)
C2	0.0442 (7)	0.0324 (6)	0.0425 (7)	−0.0105 (5)	−0.0031 (5)	−0.0029 (5)
C3	0.0368 (6)	0.0330 (6)	0.0366 (6)	−0.0104 (5)	0.0008 (5)	−0.0046 (5)
C4	0.0385 (6)	0.0328 (6)	0.0413 (6)	−0.0054 (5)	0.0013 (5)	−0.0093 (5)
C5	0.0450 (7)	0.0263 (5)	0.0438 (7)	−0.0075 (5)	−0.0038 (5)	−0.0050 (5)
C6	0.0384 (6)	0.0307 (6)	0.0372 (6)	−0.0106 (5)	−0.0021 (5)	−0.0029 (5)
C7	0.0348 (6)	0.0307 (6)	0.0367 (6)	−0.0080 (4)	−0.0009 (5)	−0.0038 (4)
C8	0.0374 (6)	0.0290 (6)	0.0389 (6)	−0.0091 (4)	−0.0014 (5)	−0.0043 (4)
C9	0.0552 (8)	0.0362 (7)	0.0657 (9)	−0.0042 (6)	0.0124 (7)	−0.0132 (6)
C10	0.0528 (8)	0.0307 (6)	0.0715 (10)	−0.0053 (5)	0.0069 (7)	−0.0091 (6)
F1	0.0486 (5)	0.0416 (4)	0.0609 (5)	−0.0030 (3)	0.0120 (4)	−0.0149 (4)
F2	0.0620 (5)	0.0262 (4)	0.0709 (6)	−0.0087 (3)	0.0058 (4)	−0.0084 (4)
N1	0.0592 (8)	0.0508 (7)	0.0578 (7)	−0.0212 (6)	0.0136 (6)	−0.0053 (6)
N2	0.0555 (7)	0.0487 (7)	0.0587 (7)	−0.0205 (6)	0.0065 (6)	0.0002 (6)
N3	0.0470 (6)	0.0279 (5)	0.0627 (7)	−0.0106 (4)	0.0132 (5)	−0.0051 (5)
N4	0.0420 (6)	0.0344 (5)	0.0564 (7)	−0.0093 (4)	0.0126 (5)	−0.0075 (5)

Geometric parameters (Å, º) top

C1—N1	1.1425 (17)	C7—C8	1.4354 (16)
C1—C3	1.4330 (17)	C8—N3	1.3618 (16)
C2—N2	1.1408 (17)	C9—N4	1.4485 (18)
C2—C6	1.4310 (17)	C9—C10	1.495 (2)
C3—C8	1.3973 (17)	C9—H9A	0.9700
C3—C4	1.4116 (17)	C9—H9B	0.9700
C4—F1	1.3481 (14)	C10—N3	1.4537 (18)
C4—C5	1.3492 (18)	C10—H10A	0.9700
C5—F2	1.3465 (14)	C10—H10B	0.9700
C5—C6	1.4081 (18)	N3—H3	0.8600
C6—C7	1.4007 (16)	N4—H4	0.8599
C7—N4	1.3580 (16)

N1—C1—C3	177.89 (14)	C3—C8—C7	118.45 (11)
N2—C2—C6	179.11 (14)	N4—C9—C10	110.40 (12)
C8—C3—C4	121.41 (11)	N4—C9—H9A	109.6
C8—C3—C1	119.68 (11)	C10—C9—H9A	109.6
C4—C3—C1	118.89 (11)	N4—C9—H9B	109.6
F1—C4—C5	121.20 (11)	C10—C9—H9B	109.6
F1—C4—C3	118.67 (11)	H9A—C9—H9B	108.1
C5—C4—C3	120.12 (11)	N3—C10—C9	109.85 (12)
F2—C5—C4	121.21 (11)	N3—C10—H10A	109.7
F2—C5—C6	118.54 (11)	C9—C10—H10A	109.7
C4—C5—C6	120.23 (11)	N3—C10—H10B	109.7
C7—C6—C5	121.40 (11)	C9—C10—H10B	109.7
C7—C6—C2	120.11 (11)	H10A—C10—H10B	108.2
C5—C6—C2	118.48 (11)	C8—N3—C10	120.46 (11)
N4—C7—C6	122.84 (11)	C8—N3—H3	114.4
N4—C7—C8	118.78 (11)	C10—N3—H3	118.1
C6—C7—C8	118.36 (11)	C7—N4—C9	121.10 (11)
N3—C8—C3	122.59 (11)	C7—N4—H4	121.1
N3—C8—C7	118.94 (11)	C9—N4—H4	116.3

C8—C3—C4—F1	−178.24 (11)	C4—C3—C8—N3	179.46 (12)
C1—C3—C4—F1	3.43 (18)	C1—C3—C8—N3	−2.24 (19)
C1—C3—C4—C5	−177.99 (11)	C4—C3—C8—C7	0.62 (19)
F1—C4—C5—F2	−0.2 (2)	C1—C3—C8—C7	178.93 (10)
C3—C4—C5—F2	−178.78 (11)	N4—C7—C8—N3	1.12 (19)
F1—C4—C5—C6	178.02 (11)	C6—C7—C8—N3	179.76 (11)
C3—C4—C5—C6	−0.5 (2)	N4—C7—C8—C3	180.00 (11)
F2—C5—C6—C7	178.04 (11)	C6—C7—C8—C3	−1.37 (18)
C4—C5—C6—C7	−0.3 (2)	N4—C9—C10—N3	−50.23 (18)
F2—C5—C6—C2	−1.96 (18)	C3—C8—N3—C10	164.48 (13)
C4—C5—C6—C2	179.72 (11)	C7—C8—N3—C10	−16.7 (2)
C5—C6—C7—N4	179.80 (11)	C9—C10—N3—C8	41.7 (2)
C2—C6—C7—N4	−0.20 (19)	C6—C7—N4—C9	167.19 (13)
C5—C6—C7—C8	1.22 (19)	C8—C7—N4—C9	−14.2 (2)
C2—C6—C7—C8	−178.78 (10)	C10—C9—N4—C7	39.5 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N3—H3···N1ⁱ	0.86	2.29	3.075 (2)	152
N4—H4···N2ⁱⁱ	0.86	2.21	3.0358 (19)	160

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x−1, −y, −z+2.

Experimental details

Crystal data
Chemical formula	C₁₀H₆F₂N₄
M_r	220.19
Crystal system, space group	Triclinic, P1
Temperature (K)	293
a, b, c (Å)	5.2173 (9), 8.7011 (15), 11.1453 (19)
α, β, γ (°)	75.545 (2), 81.854 (2), 76.427 (2)
V (Å³)	474.40 (14)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.13
Crystal size (mm)	0.28 × 0.24 × 0.16

Data collection
Diffractometer	Bruker APEXII CCD diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 2003)
T_min, T_max	0.964, 0.980
No. of measured, independent and observed [I > 2σ(I)] reflections	4155, 2141, 1816
R_int	0.026
(sin θ/λ)_max (Å⁻¹)	0.652

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.043, 0.140, 1.06
No. of reflections	2141
No. of parameters	145
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.29, −0.23

Computer programs: APEX2 (Bruker, 2007), SAINT (Bruker, 2007), SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 2005).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N3—H3···N1ⁱ	0.86	2.29	3.075 (2)	152
N4—H4···N2ⁱⁱ	0.86	2.21	3.0358 (19)	160

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x−1, −y, −z+2.

References

Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19. CrossRef Web of Science Google Scholar
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Meazza, G., Bettarini, F. & Fornara, L. (2007). WO Patent No. 2007101587. Google Scholar
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doi:10.1107/S1600536813003206

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