2,6-Dichloro­pyridine-3,5-dicarbonitrile

Adrian Woiczechowski-Pop; Richard A Varga; Anamaria Terec; Ion Grosu

doi:10.1107/S160053681003758X

. 2010 Sep 25;66(Pt 10):o2638. doi: 10.1107/S160053681003758X

2,6-Dichloropyridine-3,5-dicarbonitrile

Adrian Woiczechowski-Pop ^a,^*, Richard A Varga ^b, Anamaria Terec ^a, Ion Grosu ^a

PMCID: PMC2983305 PMID: 21587610

Abstract

In the crystal, essentially planar (r.m.s. deviation = 0.003 Å) molecules of the title compound, C₇HCl₂N₃, form chains along the b axis by means of C—H⋯N interactions. These chains are further linked into layers parallel to the ab plane by C—Cl⋯N interactions.

Related literature

For the structures of related pyridine derivatives, see: Boer et al. (1972 ▶); Clegg et al. (1997 ▶); Julia et al. (1983 ▶); Schlosser et al. (2006 ▶); Schmidt et al. (2005 ▶); Smith et al. (2008 ▶). For more information on the synthesis of 2,6-dichloropyridine-3,5-dicarbonitrile, see: Duindam et al. (1993 ▶). For compounds obtained from 2,6-dichloropyridine-3,5-dicarbonitrile, see: Katz et al. (2005 ▶); Vilarelle et al. (2004 ▶).

Experimental

Crystal data

C₇HCl₂N₃
M _r = 198.01
Orthorhombic,
a = 6.8473 (9) Å
b = 12.1307 (15) Å
c = 19.430 (3) Å
V = 1613.9 (4) Å³
Z = 8
Mo Kα radiation
μ = 0.74 mm⁻¹
T = 297 K
0.41 × 0.39 × 0.39 mm

Data collection

Bruker SMART APEX CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2000 ▶) T _min = 0.751, T _max = 0.761
10614 measured reflections
1420 independent reflections
1328 reflections with I > 2σ(I)
R _int = 0.049

Refinement

R[F ² > 2σ(F ²)] = 0.067
wR(F ²) = 0.133
S = 1.29
1420 reflections
109 parameters
H-atom parameters constrained
Δρ_max = 0.25 e Å⁻³
Δρ_min = −0.33 e Å⁻³

Data collection: SMART (Bruker, 2000 ▶); cell refinement: SAINT-Plus (Bruker, 2001 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg & Putz, 2006 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablocks I, New_Global_Publ_Block. DOI: 10.1107/S160053681003758X/ya2129sup1.cif

e-66-o2638-sup1.cif^{(14.1KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S160053681003758X/ya2129Isup2.hkl

e-66-o2638-Isup2.hkl^{(70.2KB, hkl)}

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

Table 1. Intermolecular interactions (Å, °).

D—X⋯A	D—X	X⋯A	D⋯A	D—X⋯A
C3—H3⋯N1ⁱ	0.93	2.54	3.412 (5)	157
C1—Cl1⋯N2ⁱⁱ	1.71 (1)	3.24 (1)	4.820 (5)	152 (1)
C5—Cl2⋯N3ⁱⁱⁱ	1.72 (1)	3.28 (1)	4.851 (6)	151 (1)

Open in a new tab

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

Acknowledgments

This work was supported by the National University Research Council of Romania (CNCSIS–UEFISCSU); project number PNII–IDEI 570/2007. We thank Dr Ciprian Rat for helpful disussions and advice.

supplementary crystallographic information

Comment

Some pyridine derivatives are known to be important intermediates in pharmaceutical and medicinal chemistry. They can be used for the synthesis of various compounds having antibacterial, antianaphilactic, antipyretic, antiallergic or anticancer properties (Vilarelle et al., 2004). Lately, pyridine derivatives were used in the synthesis of cage molecules, supramolecular structures which are important as tools for the study of molecular encapsulation and host–guest interactions (Katz et al., 2005).

Relatively few crystal structures of pyridines substituted in positions 2 and 6 with chlorine atoms were published (Boer et al., 1972; Clegg et al., 1997; Julia et al., 1983; Schlosser et al., 2006; Schmidt et al., 2005; Smith et al., 2008). The synthesis of the title compound has been reported some years ago (Duindam et al., 1993), however its crystal structure has not yet been determined, even though electron withdrawing CN groups, causing considerable acidity of the H atom in position 4, as well as chlorine substituents at the pyridine atoms adjacent to the endocyclic N atom, may give rise to important non-conventional intermolecular interactions. Therefore, one may expect that structural study of the title compound may provide some non-trivial information.

Molecule of the title compound (Fig. 1) is essentially planar; the N2 and N3 atoms deviate from the pyridine plane by 0.060 (4) Å and 0.026 (4) Å respectively.

The molecules are linked by means of C3—H3···N1ⁱ ineractions (Table 1) into infinite chains running along the b axis. The pyridine rings in the adjacent molecules of these chains are not coplanar, but rather form substantial dihedral angle with one another [56.5 (1)°]. The chains are further linked via C1—Cl1···N2ⁱⁱ and C5—Cl2···N3ⁱⁱⁱ interactions into layers parallel to the ab-plane (Table 1; Fig. 2).

Experimental

A mixture of malononitrile (5 g, 75.69 mmol, 2 equiv.), triethyl orthoformate (5.61 g, 37.84 mmol, 1 equiv.) and pyridine (2.99 g, 37.84 mmol, 1 equiv.) was allowed to reflux for 20 minutes, then concentrated HCl was added at 80°C. The mixture was cooled to room temperature and water (20 ml) was added. The formed precipitate was collected by filtration, washed successively with water, ethanol and diethylether to afford the intermediate 2-amino-6-chloropyridine-3,5-dicarbonitrile (9.74 g, 96%). To a solution of 2-amino-6-chloropyridine-3,5-dicarbonitrile (3 g, 16.8 mmol, 1 equiv.) and CuCl₂ (3.39 g, 25.2 mmol, 1.5 equiv.) in dry CH₃CN (150 ml), isopentyl nitrite was added (2.95 g, 25.2 mmol, 1.5 equiv.). The mixture was heated at 65°C for 5 h. The solution was acidified (HCl, 2 N) to pH=3, extracted with CH₂Cl₂ (3×50 ml) and dried with Na₂SO₄. The solvent was removed under reduced pressure and the crude product was purified by flash chromatography using CH₂Cl₂ as eluent to yield 2,6-dichloropyridine-3,5-dicarbonitrile as a colourless solid (2.97 g, 89%). The crystals were obtained by slow evaporation of the solvent from solution of the title compound in dichloromethane.