5,6-Bis(pyridin-2-yl)-2,3-di­hydro­pyrazine

Posel, M.; Stoeckli-Evans, H.

doi:10.1107/S241431461601467X

organic compounds

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ISSN: 2414-3146

Volume 1| Part 9| September 2016| x161467

doi:10.1107/S241431461601467X

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5,6-Bis(pyridin-2-yl)-2,3-dihydropyrazine

Maciej Posel ^a and Helen Stoeckli-Evans ^b ^*

^aInstitute of Chemistry, University of Neuchâtel, Av de Bellevaux 51, CH-2000 Neuchâtel, Switzerland, and ^bInstitute of Physics, University of Neuchâtel, rue Emile-Argand 11, CH-2000 Neuchâtel, Switzerland
^*Correspondence e-mail: helen.stoeckli-evans@unine.ch

Edited by K. Fejfarova, Institute of Biotechnology CAS, Czech Republic (Received 6 September 2016; accepted 16 September 2016; online 23 September 2016)

The title compound, C₁₄H₁₂N₄, has approximate twofold rotational symmetry. The pseudo-twofold axis bisects the C—C bonds of the dihydropyrazine ring, which has a screw–boat conformation. The two pyridine rings are inclined to the mean plane of the dihydropyrazine ring by 30.78 (11) and 39.37 (9)°, and to one another by 62.53 (10)°. The pyridine N atoms are cis to one another, with an N⋯N nonbonded distance of 3.101 (2) Å. In the crystal, molecules are linked via a pair of N—H⋯N hydrogen bonds, forming inversion dimers with an R₂²(6) ring motif. These units are linked by further N—H⋯H hydrogen bonds, forming layers parallel to (302). The layers are linked by C—H⋯π interactions, forming a three-dimensional framework.

Keywords: crystal structure; dihydropyrazine; pyridine; C—H⋯N hydrogen bonding; C—H⋯π interactions; three-dimensional framework.

CCDC reference: 1504682

Structure description

The title compound (Fig. 1) has approximate twofold rotation symmetry. The pseudo-twofold axis bisects the C—C bonds of the dihydropyrazine ring, which has a screw-boat conformation. The two pyridine rings (N3/C5–C6 and N4/C10–C14) are inclined to the mean plane of the dihydropyrazine ring (N1/N2/C1–C4) by 30.78 (11) and 39.37 (9)°, respectively, and to one another by 62.53 (10)°. The pyridine N atoms are cis to one another, with an N⋯N nonbonded distance of 3.101 (2) Å.

Figure 1
A view of the molecular structure of the title compound, showing the atom labelling. Displacement ellipsoids are drawn at the 50% probability level.

In the crystal, molecules are linked via a pair of N—H⋯N hydrogen bonds (Table 1), forming inversion dimers with an R₂²(6) ring motif, which is clearly visible in Fig. 2. These units are linked by further N—H⋯H hydrogen bonds, forming layers parallel to (302) (see Table 1 and Fig. 2). The layers are linked by C—H⋯π interactions, forming a three-dimensional framework (Table 1).

Table 1
Hydrogen-bond geometry (Å, °)

Cg3 is the centroid of ring N4/C10–C14.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C12—H12⋯N3ⁱ	0.997 (19)	2.552 (19)	3.382 (3)	140.5 (15)
C13—H13⋯N1ⁱⁱ	0.959 (19)	2.557 (19)	3.432 (3)	151.8 (14)
C14—H14⋯N4ⁱⁱⁱ	0.962 (18)	2.518 (19)	3.375 (3)	148.4 (15)
C3—H3A⋯Cg3^iv	1.00 (2)	2.78 (2)	3.645 (3)	144.7 (15)
Symmetry codes: (i) $[-x+{\script{1\over 2}}, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (ii) x, y+1, z; (iii) -x, -y+1, -z+1; (iv) $[-x-{\script{1\over 2}}, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Figure 2
A view along the a axis of the crystal packing of the title compound. The C—H⋯N hydrogen bonds are shown as dashed lines (see Table 1

) and, for clarity, only the H atoms involved in the intermolecular interactions have been included.

The title compound was prepared as a precursor for the synthesis of 2,3-bis(pyridin-2-yl)pyrazine. In this pyrazine analogue, whose structure has been reported (Huang et al., 1991 ; Robertson et al., 1998 ; Posel & Stoeckli-Evans, 2016 ), the whole molecule is generated by twofold rotational symmetry; the twofold axis bisects the C_ar—C_ar bonds of the pyrazine ring. The pyridine rings are inclined to the pyrazine ring by 42.00 (12)° and to one another by 53.92 (12)° (Posel & Stoeckli-Evans, 2016). The pyridine N atoms are cis to one another, with an N⋯N nonbonded distance of 2.967 (3) Å.

Synthesis and crystallization

The title compound was prepared by a condensation reaction following the method of Goodwin & Lions (1959 ). A round-bottomed flask, fitted with a reflux condenser and a dropping funnel, was charged with a solution of 4.25 g (0.02 mol) of 1,2-di(pyridin-2-yl)ethane-1,2-dione in 20 ml of dry ethanol. A solution of 1.2 g (0.021 mol) of ethylenediamine was then added dropwise and the mixture refluxed for 2 h. After cooling, the mixture was filtered to give a brown product which was washed many times with ethanol, giving a beige solid. On recrystallization from ethanol solution, colourless block-like crystals were obtained (yield 2.8 g, 59%; m.p. 461 K). The IR (KBr disk, cm⁻¹) spectrum is shown in Fig. 3.

Figure 3
The IR spectrum of the title compound.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. All the H atoms were located in difference Fourier maps and freely refined.

Table 2
Experimental details

Crystal data
Chemical formula	C₁₄H₁₂N₄
M_r	236.28
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	293
a, b, c (Å)	7.3989 (16), 9.6247 (10), 17.483 (2)
β (°)	91.112 (13)
V (Å³)	1244.8 (3)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.08
Crystal size (mm)	0.76 × 0.57 × 0.46

Data collection
Diffractometer	Stoe–Siemens AED2 four-circle
No. of measured, independent and observed [I > 2σ(I)] reflections	2191, 2191, 1458
R_int	0.0
(sin θ/λ)_max (Å⁻¹)	0.594

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.040, 0.100, 0.98
No. of reflections	2191
No. of parameters	212
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.12, −0.12
Computer programs: STADI4 and X-RED (Stoe & Cie, 1997 ), SHELXS97 (Sheldrick, 2008 ), Mercury (Macrae et al., 2008 ), SHELXL2014 (Sheldrick, 2015 ), PLATON (Spek, 2009 ) and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 1504682

Crystal structure: contains datablocks I, Global. DOI: 10.1107/S241431461601467X/ff4009sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S241431461601467X/ff4009Isup2.hkl

Supporting information file. DOI: 10.1107/S241431461601467X/ff4009Isup3.cml

checkCIF report

Computing details top

Data collection: STADI4 Software (Stoe & Cie, 1997); cell refinement: STADI4 Software (Stoe & Cie, 1997); data reduction: X-RED Software (Stoe & Cie, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015), PLATON (Spek, 2009) and publCIF (Westrip, 2010).

5,6-Bis(pyridin-2-yl)-2,3-dihydropyrazine top

Crystal data top

C₁₄H₁₂N₄	F(000) = 496
M_r = 236.28	D_x = 1.261 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71069 Å
a = 7.3989 (16) Å	Cell parameters from 21 reflections
b = 9.6247 (10) Å	θ = 14.0–19.5°
c = 17.483 (2) Å	µ = 0.08 mm⁻¹
β = 91.112 (13)°	T = 293 K
V = 1244.8 (3) Å³	Block, colourless
Z = 4	0.76 × 0.57 × 0.46 mm

Data collection top

Stoe–Siemens AED2 four-circle diffractometer	R_int = 0.0
Radiation source: fine-focus sealed tube	θ_max = 25.0°, θ_min = 2.3°
Plane graphite monochromator	h = −8→8
ω/2θ scans	k = 0→−11
2191 measured reflections	l = 0→20
2191 independent reflections	1 standard reflections every 60 min
1458 reflections with I > 2σ(I)	intensity decay: 1%

Refinement top

Refinement on F²	Hydrogen site location: difference Fourier map
Least-squares matrix: full	All H-atom parameters refined
R[F² > 2σ(F²)] = 0.040	w = 1/[σ²(F_o²) + (0.0454P)²] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.100	(Δ/σ)_max < 0.001
S = 0.98	Δρ_max = 0.12 e Å⁻³
2191 reflections	Δρ_min = −0.12 e Å⁻³
212 parameters	Extinction correction: SHELXL2014 (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.038 (3)

Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
N1	0.0009 (2)	0.06093 (16)	0.36192 (10)	0.0601 (5)
N2	−0.0463 (2)	0.25389 (16)	0.23810 (9)	0.0522 (4)
N3	0.3603 (2)	0.29146 (17)	0.38948 (9)	0.0571 (5)
N4	0.0087 (2)	0.46622 (15)	0.39540 (8)	0.0514 (4)
C1	0.0793 (2)	0.17892 (18)	0.36041 (10)	0.0434 (5)
C2	0.0252 (2)	0.28713 (18)	0.30252 (10)	0.0416 (4)
C3	−0.0819 (3)	0.1046 (2)	0.22844 (14)	0.0619 (6)
H3A	−0.177 (3)	0.0990 (19)	0.1872 (10)	0.061 (5)*
H3B	0.030 (3)	0.056 (2)	0.2118 (11)	0.072 (7)*
C4	−0.1407 (3)	0.0426 (3)	0.30222 (15)	0.0682 (7)
H4A	−0.170 (3)	−0.055 (2)	0.2994 (11)	0.072 (6)*
H4B	−0.257 (3)	0.094 (2)	0.3209 (12)	0.084 (7)*
C5	0.2338 (2)	0.20503 (18)	0.41447 (10)	0.0436 (5)
C6	0.2448 (3)	0.1405 (2)	0.48488 (12)	0.0612 (6)
H6	0.152 (3)	0.080 (2)	0.4998 (11)	0.072 (7)*
C7	0.3902 (4)	0.1693 (3)	0.53272 (14)	0.0807 (8)
H7	0.398 (4)	0.119 (3)	0.5830 (16)	0.130 (10)*
C8	0.5193 (4)	0.2576 (3)	0.50801 (16)	0.0894 (9)
H8	0.618 (4)	0.280 (3)	0.5401 (15)	0.123 (10)*
C9	0.5026 (3)	0.3147 (3)	0.43628 (15)	0.0772 (7)
H9	0.590 (4)	0.381 (3)	0.4150 (14)	0.111 (9)*
C10	0.0418 (2)	0.43602 (18)	0.32216 (9)	0.0407 (4)
C11	0.0780 (2)	0.5372 (2)	0.26831 (11)	0.0463 (5)
H11	0.102 (2)	0.5066 (19)	0.2143 (10)	0.060 (6)*
C12	0.0824 (3)	0.6743 (2)	0.29078 (12)	0.0525 (5)
H12	0.104 (3)	0.751 (2)	0.2537 (11)	0.069 (6)*
C13	0.0502 (3)	0.7064 (2)	0.36572 (12)	0.0549 (5)
H13	0.059 (2)	0.801 (2)	0.3820 (10)	0.059 (6)*
C14	0.0137 (3)	0.6004 (2)	0.41552 (12)	0.0575 (6)
H14	−0.009 (2)	0.6193 (19)	0.4685 (11)	0.063 (6)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0611 (11)	0.0446 (10)	0.0739 (12)	−0.0043 (8)	−0.0209 (9)	0.0015 (8)
N2	0.0511 (10)	0.0552 (10)	0.0500 (9)	0.0033 (8)	−0.0108 (8)	−0.0091 (8)
N3	0.0518 (10)	0.0652 (11)	0.0537 (10)	−0.0077 (9)	−0.0117 (8)	−0.0022 (8)
N4	0.0715 (11)	0.0417 (9)	0.0409 (9)	0.0055 (8)	0.0014 (8)	0.0007 (7)
C1	0.0437 (10)	0.0397 (11)	0.0465 (10)	0.0035 (9)	−0.0059 (8)	−0.0055 (8)
C2	0.0375 (9)	0.0444 (11)	0.0427 (10)	0.0020 (8)	−0.0047 (8)	−0.0033 (8)
C3	0.0565 (14)	0.0585 (14)	0.0698 (15)	0.0046 (11)	−0.0250 (12)	−0.0186 (12)
C4	0.0669 (16)	0.0477 (14)	0.0888 (18)	−0.0108 (12)	−0.0287 (13)	−0.0013 (12)
C5	0.0464 (11)	0.0395 (10)	0.0446 (11)	0.0054 (9)	−0.0075 (8)	−0.0058 (8)
C6	0.0641 (14)	0.0639 (14)	0.0552 (13)	0.0012 (12)	−0.0108 (11)	0.0080 (11)
C7	0.091 (2)	0.0889 (19)	0.0607 (15)	0.0032 (16)	−0.0269 (14)	0.0100 (14)
C8	0.0767 (18)	0.109 (2)	0.0806 (18)	−0.0105 (16)	−0.0418 (15)	0.0021 (16)
C9	0.0614 (15)	0.0933 (19)	0.0761 (16)	−0.0177 (14)	−0.0210 (13)	0.0041 (14)
C10	0.0391 (10)	0.0441 (10)	0.0386 (10)	0.0033 (8)	−0.0045 (8)	0.0023 (8)
C11	0.0428 (11)	0.0535 (13)	0.0424 (11)	0.0010 (9)	−0.0013 (8)	0.0044 (9)
C12	0.0500 (12)	0.0498 (12)	0.0577 (13)	−0.0048 (10)	−0.0018 (9)	0.0137 (11)
C13	0.0673 (14)	0.0387 (12)	0.0582 (13)	0.0018 (10)	−0.0110 (10)	0.0018 (10)
C14	0.0855 (16)	0.0435 (12)	0.0434 (12)	0.0093 (10)	−0.0005 (11)	−0.0025 (10)

Geometric parameters (Å, º) top

N1—C1	1.276 (2)	C5—C6	1.380 (3)
N1—C4	1.475 (2)	C6—C7	1.378 (3)
N2—C2	1.276 (2)	C6—H6	0.94 (2)
N2—C3	1.470 (2)	C7—C8	1.355 (4)
N3—C5	1.333 (2)	C7—H7	1.01 (3)
N3—C9	1.339 (3)	C8—C9	1.373 (4)
N4—C14	1.339 (2)	C8—H8	0.94 (3)
N4—C10	1.340 (2)	C9—H9	0.98 (3)
C1—C5	1.490 (2)	C10—C11	1.384 (2)
C1—C2	1.501 (2)	C11—C12	1.377 (3)
C2—C10	1.478 (2)	C11—H11	1.007 (18)
C3—C4	1.494 (3)	C12—C13	1.372 (3)
C3—H3A	1.00 (2)	C12—H12	1.00 (2)
C3—H3B	1.00 (2)	C13—C14	1.372 (3)
C4—H4A	0.96 (2)	C13—H13	0.959 (19)
C4—H4B	1.05 (2)	C14—H14	0.962 (18)

C1—N1—C4	114.15 (17)	C7—C6—H6	121.4 (13)
C2—N2—C3	114.63 (16)	C5—C6—H6	119.6 (13)
C5—N3—C9	116.93 (19)	C8—C7—C6	118.6 (2)
C14—N4—C10	117.10 (16)	C8—C7—H7	123.5 (16)
N1—C1—C5	118.72 (16)	C6—C7—H7	117.7 (16)
N1—C1—C2	121.07 (16)	C7—C8—C9	119.4 (2)
C5—C1—C2	120.12 (16)	C7—C8—H8	119.8 (17)
N2—C2—C10	118.64 (16)	C9—C8—H8	120.8 (17)
N2—C2—C1	121.45 (16)	N3—C9—C8	123.1 (3)
C10—C2—C1	119.75 (15)	N3—C9—H9	113.0 (15)
N2—C3—C4	110.23 (18)	C8—C9—H9	123.8 (15)
N2—C3—H3A	104.9 (11)	N4—C10—C11	122.58 (17)
C4—C3—H3A	112.8 (11)	N4—C10—C2	114.60 (15)
N2—C3—H3B	109.9 (12)	C11—C10—C2	122.71 (16)
C4—C3—H3B	108.9 (12)	C12—C11—C10	118.94 (18)
H3A—C3—H3B	110.0 (16)	C12—C11—H11	123.0 (11)
N1—C4—C3	110.40 (19)	C10—C11—H11	118.1 (11)
N1—C4—H4A	108.2 (12)	C13—C12—C11	119.02 (19)
C3—C4—H4A	114.4 (12)	C13—C12—H12	119.0 (11)
N1—C4—H4B	107.3 (12)	C11—C12—H12	122.0 (11)
C3—C4—H4B	109.6 (12)	C12—C13—C14	118.60 (19)
H4A—C4—H4B	106.6 (17)	C12—C13—H13	119.1 (11)
N3—C5—C6	122.92 (17)	C14—C13—H13	122.2 (11)
N3—C5—C1	115.63 (16)	N4—C14—C13	123.75 (19)
C6—C5—C1	121.44 (18)	N4—C14—H14	115.5 (11)
C7—C6—C5	118.9 (2)	C13—C14—H14	120.7 (11)

C4—N1—C1—C5	−175.57 (18)	C1—C5—C6—C7	−179.59 (19)
C4—N1—C1—C2	0.9 (3)	C5—C6—C7—C8	−1.6 (4)
C3—N2—C2—C10	−171.25 (17)	C6—C7—C8—C9	−0.5 (4)
C3—N2—C2—C1	4.1 (3)	C5—N3—C9—C8	−2.0 (4)
N1—C1—C2—N2	−26.3 (3)	C7—C8—C9—N3	2.3 (5)
C5—C1—C2—N2	150.18 (17)	C14—N4—C10—C11	−0.7 (3)
N1—C1—C2—C10	149.06 (18)	C14—N4—C10—C2	−177.04 (17)
C5—C1—C2—C10	−34.5 (2)	N2—C2—C10—N4	140.74 (17)
C2—N2—C3—C4	36.7 (2)	C1—C2—C10—N4	−34.7 (2)
C1—N1—C4—C3	39.9 (3)	N2—C2—C10—C11	−35.6 (3)
N2—C3—C4—N1	−59.8 (3)	C1—C2—C10—C11	148.93 (17)
C9—N3—C5—C6	−0.2 (3)	N4—C10—C11—C12	0.8 (3)
C9—N3—C5—C1	−178.73 (18)	C2—C10—C11—C12	176.81 (17)
N1—C1—C5—N3	148.95 (18)	C10—C11—C12—C13	−0.2 (3)
C2—C1—C5—N3	−27.6 (2)	C11—C12—C13—C14	−0.4 (3)
N1—C1—C5—C6	−29.6 (3)	C10—N4—C14—C13	0.1 (3)
C2—C1—C5—C6	153.85 (18)	C12—C13—C14—N4	0.5 (3)
N3—C5—C6—C7	2.0 (3)

Hydrogen-bond geometry (Å, º) top

Cg3 is the centroid of ring N4/C10-C14.

D—H···A	D—H	H···A	D···A	D—H···A
C12—H12···N3ⁱ	0.997 (19)	2.552 (19)	3.382 (3)	140.5 (15)
C13—H13···N1ⁱⁱ	0.959 (19)	2.557 (19)	3.432 (3)	151.8 (14)
C14—H14···N4ⁱⁱⁱ	0.962 (18)	2.518 (19)	3.375 (3)	148.4 (15)
C3—H3A···Cg3^iv	1.00 (2)	2.78 (2)	3.645 (3)	144.7 (15)

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

Acknowledgements

We are grateful to the Swiss National Science Foundation and the University of Neuchâtel for financial support.

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