Quinoxaline-2-carbonitrile

In the title compound, C₉H₅N₃, the quinoxaline ring is essentially planar, with a maximum deviation of 0.012 (1) Å. Short inter­molecular distances between the centroids of the 2,3-dihydro­pyrazine and benzene rings [3.6490 (5) Å] indicate the existence of π...π inter­actions. In the crystal packing, the mol­ecules are linked via two pairs of inter­molecular C—H...N inter­actions, forming R²₂ (8) and R²₂ (10) ring motifs; these mol­ecules are further linked into a two-dimensional network parallel to (1 0 2) via another C–H...N inter­action.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.001 Å
• R factor = 0.047
• wR factor = 0.135
• Data-to-parameter ratio = 21.1

checkCIF/PLATON results

No syntax errors found



Alert level C
DIFMX01_ALERT_2_C  The maximum difference density is > 0.1*ZMAX*0.75
            _refine_diff_density_max given =      0.527
            Test value =      0.525
DIFMX02_ALERT_1_C  The maximum difference density is > 0.1*ZMAX*0.75
            The relevant atom site should be identified.
PLAT094_ALERT_2_C Ratio of Maximum / Minimum Residual Density ....       2.26
PLAT230_ALERT_2_C Hirshfeld Test Diff for    C8     --  C9      ..       6.30 su
PLAT371_ALERT_2_C Long   C(sp2)-C(sp1) Bond  C8     -   C9     ...       1.45 Ang.
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600         27

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   6 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
   4 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
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Heterocyclic molecules containing a cyano group are useful as drug intermediates. The development of new pathways leading to efficient synthesis of heterocycles with diversity in skeleton and functional groups is an important field of research in both synthetic and medicinal chemistry. Recently, we have synthesized a number of cyano N-heterocyclic compounds using triselenium dicyanide (TSD) (Goswami et al., 2007, 2009). Herein we report the synthesis of 2-cyanoquinoxaline from quinoxaline under microwave irradiation and its molecular structure.

The bond lengths (Allen et al., 1987) and angles in the title compound (Fig. 1) are within normal ranges. The quinoxaline ring (N1/N2/C1-C8) is essentially planar, with the maximum deviation of 0.012 (1) Å for atom C5. Short intermolecular distances between the centroids of the pyrazine (N1/N2/C1/C6-C8) and benzene rings (C1-C6) [3.6490 (5) Å] indicate the existence of π···π interactions.

In the crystal packing (Fig. 2), the molecules are linked via pairs of intermolecular C2—H2···N1 and C7—H7···N3 interactions, forming R²₂ (8) and R²₂ (10) ring motifs (Bernstein et al., 1995) and these molecules are further linked into two-dimensional networks parallel to plane (1 0 2) via C4–H4···N2 interactions.

Related literature

For the synthesis of cyano N-heterocyclic compounds, see: Goswami et al. (2007, 2009). For reference bond lengths, see: Allen et al. (1987). For hydrogen-bond motifs, see: Bernstein et al. (1995). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).

S2. Experimental

A thoroughly ground mixture of selenium dioxide (1.32 g, 12 mmol) and malononitrile (0.26 g, 4 mmol) in 4-5 drops of DMSO was kept stirring in an open-mouth conical flask. The mixture became reddish-brown after 7 min. An exothermic reaction began in the next 10 minutes when triselenium dicyanide was formed. The heterocyclic substrate quinoxaline (0.39 g, 3 mmol) was added to the mixture after the termination of the exothermic reaction. The conical flask was placed in a domestic microwave oven at 240 W for 20 min. The progress of the reaction was monitored by TLC. After completion of the reaction, water was added and the mixture was extracted with chloroform. The organic layer was washed with saturated brine and dried over MgSO₄ and followed by evaporation with a rotary evaporator under low pressure to afford a light yellow substance. This was purified on silica gel (60-120 mesh) column chromatography eluting with petroleum ether (boiling point, 60-80° C) to give the compound (0.34 g, 74 %) as a crystalline solid.

S3. Refinement

All H atoms were located in a difference Fourier map and refined freely.

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures

	Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids for non-H atoms and the atom-numbering scheme.
	Fig. 2. The crystal structure of the title compound viewed along the a axis. Intermolecular interactions are shown in dashed lines.

Quinoxaline-2-carbonitrile

Crystal data

C9H5N3	F(000) = 320
Mr = 155.16	Dx = 1.399 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 4710 reflections
a = 3.8055 (1) Å	θ = 2.9–32.7°
b = 19.0466 (4) Å	µ = 0.09 mm^−1
c = 10.1845 (2) Å	T = 100 K
β = 93.466 (1)°	Block, yellow
V = 736.84 (3) Å^3	0.39 × 0.28 × 0.25 mm
Z = 4

Data collection

Bruker SMART APEXII CCD area-detector diffractometer	2716 independent reflections
Radiation source: fine-focus sealed tube	2183 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.023
ϕ and ω scans	θmax = 32.8°, θmin = 2.1°
Absorption correction: multi-scan (SADABS; Bruker, 2005)	h = −5→5
Tmin = 0.966, Tmax = 0.978	k = −29→21
11604 measured reflections	l = −15→14

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)] = 0.047	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.135	All H-atom parameters refined
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0782P)^2 + 0.0918P] where P = (Fo^2 + 2Fc^2)/3
2716 reflections	(Δ/σ)max = 0.001
129 parameters	Δρmax = 0.53 e Å^−3
0 restraints	Δρmin = −0.23 e Å^−3

Special details

Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.

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
N1	0.12156 (18)	0.46098 (4)	0.84114 (7)	0.01481 (16)
N2	−0.12366 (19)	0.33470 (4)	0.71846 (8)	0.01659 (17)
N3	−0.2187 (2)	0.57757 (5)	0.60971 (9)	0.0269 (2)
C1	0.1884 (2)	0.39728 (4)	0.89844 (8)	0.01344 (17)
C2	0.3822 (2)	0.39456 (5)	1.02181 (9)	0.01744 (18)
C3	0.4514 (2)	0.33059 (5)	1.07937 (10)	0.02033 (19)
C4	0.3352 (2)	0.26756 (5)	1.01678 (10)	0.0210 (2)
C5	0.1474 (2)	0.26871 (5)	0.89805 (9)	0.01857 (19)
C6	0.0674 (2)	0.33382 (4)	0.83638 (9)	0.01441 (17)
C7	−0.1868 (2)	0.39663 (4)	0.66474 (9)	0.01675 (18)
C8	−0.0633 (2)	0.45941 (4)	0.72702 (8)	0.01496 (17)
C9	−0.1450 (2)	0.52598 (5)	0.66332 (9)	0.01913 (19)
H2	0.471 (4)	0.4375 (7)	1.0662 (14)	0.030 (3)*
H3	0.591 (4)	0.3282 (7)	1.1650 (16)	0.038 (4)*
H4	0.396 (3)	0.2229 (7)	1.0622 (13)	0.028 (3)*
H5	0.057 (4)	0.2262 (7)	0.8533 (14)	0.032 (3)*
H7	−0.328 (4)	0.4008 (7)	0.5793 (14)	0.028 (3)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0154 (3)	0.0145 (3)	0.0146 (3)	0.0003 (2)	0.0014 (2)	0.0010 (2)
N2	0.0168 (3)	0.0173 (3)	0.0157 (4)	−0.0006 (2)	0.0014 (3)	−0.0016 (3)
N3	0.0328 (4)	0.0235 (4)	0.0241 (5)	0.0028 (3)	−0.0002 (3)	0.0057 (3)
C1	0.0128 (3)	0.0147 (3)	0.0130 (4)	0.0002 (2)	0.0019 (3)	0.0004 (3)
C2	0.0157 (4)	0.0218 (4)	0.0147 (4)	−0.0004 (3)	−0.0002 (3)	0.0005 (3)
C3	0.0164 (4)	0.0275 (4)	0.0170 (4)	0.0019 (3)	0.0003 (3)	0.0055 (3)
C4	0.0176 (4)	0.0208 (4)	0.0248 (5)	0.0030 (3)	0.0042 (3)	0.0088 (3)
C5	0.0179 (4)	0.0147 (4)	0.0235 (5)	0.0007 (3)	0.0036 (3)	0.0029 (3)
C6	0.0131 (3)	0.0152 (3)	0.0151 (4)	0.0000 (2)	0.0027 (3)	0.0000 (3)
C7	0.0164 (4)	0.0195 (4)	0.0142 (4)	−0.0003 (3)	0.0000 (3)	−0.0004 (3)
C8	0.0145 (3)	0.0168 (4)	0.0137 (4)	0.0005 (3)	0.0019 (3)	0.0015 (3)
C9	0.0204 (4)	0.0202 (4)	0.0167 (4)	0.0005 (3)	0.0005 (3)	0.0015 (3)

Geometric parameters (Å, º)

N1—C8	1.3220 (11)	C3—C4	1.4175 (14)
N1—C1	1.3636 (10)	C3—H3	0.995 (16)
N2—C7	1.3161 (11)	C4—C5	1.3670 (13)
N2—C6	1.3659 (11)	C4—H4	0.988 (13)
N3—C9	1.1506 (12)	C5—C6	1.4150 (11)
C1—C2	1.4190 (12)	C5—H5	0.980 (14)
C1—C6	1.4273 (11)	C7—C8	1.4202 (12)
C2—C3	1.3706 (12)	C7—H7	0.997 (14)
C2—H2	0.985 (14)	C8—C9	1.4495 (12)
C8—N1—C1	115.57 (7)	C4—C5—C6	119.57 (8)
C7—N2—C6	116.78 (7)	C4—C5—H5	123.2 (8)
N1—C1—C2	119.01 (7)	C6—C5—H5	117.2 (8)
N1—C1—C6	121.14 (8)	N2—C6—C5	119.33 (7)
C2—C1—C6	119.85 (7)	N2—C6—C1	121.28 (7)
C3—C2—C1	119.16 (8)	C5—C6—C1	119.38 (8)
C3—C2—H2	119.4 (8)	N2—C7—C8	121.44 (8)
C1—C2—H2	121.5 (8)	N2—C7—H7	120.7 (7)
C2—C3—C4	120.92 (9)	C8—C7—H7	117.9 (7)
C2—C3—H3	119.6 (8)	N1—C8—C7	123.77 (7)
C4—C3—H3	119.4 (8)	N1—C8—C9	117.52 (7)
C5—C4—C3	121.10 (8)	C7—C8—C9	118.71 (8)
C5—C4—H4	121.5 (8)	N3—C9—C8	177.49 (10)
C3—C4—H4	117.4 (8)
C8—N1—C1—C2	−179.34 (7)	C4—C5—C6—C1	0.84 (13)
C8—N1—C1—C6	0.75 (12)	N1—C1—C6—N2	−0.95 (13)
N1—C1—C2—C3	−179.68 (8)	C2—C1—C6—N2	179.14 (7)
C6—C1—C2—C3	0.24 (13)	N1—C1—C6—C5	178.94 (7)
C1—C2—C3—C4	0.62 (13)	C2—C1—C6—C5	−0.97 (12)
C2—C3—C4—C5	−0.75 (14)	C6—N2—C7—C8	−0.32 (13)
C3—C4—C5—C6	0.00 (14)	C1—N1—C8—C7	−0.38 (12)
C7—N2—C6—C5	−179.20 (7)	C1—N1—C8—C9	179.15 (7)
C7—N2—C6—C1	0.69 (12)	N2—C7—C8—N1	0.18 (14)
C4—C5—C6—N2	−179.26 (7)	N2—C7—C8—C9	−179.36 (8)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2···N1^i	0.984 (14)	2.619 (14)	3.5730 (12)	163.4 (12)
C4—H4···N2^ii	0.988 (13)	2.593 (13)	3.4268 (12)	142.0 (10)
C7—H7···N3^iii	0.998 (14)	2.540 (15)	3.5225 (12)	168.3 (12)

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