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

Bao-Hua Qu; Xiao-Chuan Jia; Jing Li; Ming-Yang He

doi:10.1107/S1600536813003206

. 2013 Feb 13;69(Pt 3):o376. doi: 10.1107/S1600536813003206

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

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

PMCID: PMC3588508 PMID: 23476563

Abstract

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,
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[F ² > 2σ(F ²)] = 0.043
wR(F ²) = 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

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.

Supplementary Material

Click here for additional data file.^{(18.7KB, cif)}

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536813003206/yk2078sup1.cif

e-69-0o376-sup1.cif^{(18.7KB, cif)}

Click here for additional data file.^{(105.3KB, hkl)}

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

e-69-0o376-Isup2.hkl^{(105.3KB, hkl)}

Click here for additional data file.^{(3.8KB, cml)}

Supplementary material file. DOI: 10.1107/S1600536813003206/yk2078Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

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

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Symmetry codes: (i) Inline graphic ; (ii) .

supplementary crystallographic information

Comment

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).

Experimental

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).