3-Cyanopyridine:Uses,Preparation and Hazard

3-Cyanopyridine(nicotinonitrile) is a valuable intermediate useful in the preparation of nicotinic acid (niacin) and nicotinamide. Nicotinamide is an essential B vitamin with antipellagra activity.

Uses

3-Cyanopyridine (3-CNpy) can act as a bridging or terminal ligand in transition metal coordination polymers. The compounds [MIIBr2(3-CNpy)4] with M = Mn, Fe, Co, Ni (1a–4a) consist of individual complexes, in which the metal atom is octahedrally coordinated by two bromine atoms and four 3-cyanopyridine ligands, which coordinate through their pyridine N atoms only. Thermal decomposition at around 160 °C leads to the release of two 3-cyanopyridine molecules and the formation of [MIIBr2(3-CNpy)2]n with M = Mn, Fe, Co, Ni (1b–4b). For 3b and 4b two polymorphs were observed each (α-3b, β-3b, α-4b, β-4b). In all six phases the metal atoms are linked by bromine bridges into [MIIBr2]n chains. The 3-cyanopyridine ligands again act as terminal ligands coordinating with their pyridine N atoms. Upon further heating to around 250 °C, the compounds [MIIBr2(3-CNpy)1]n with M = Mn, Fe, Co, Ni (1c–4c) are obtained. 1c–4c are again built up from [MIIBr2]n chains with lateral 3-CNpy ligands, but additionally the cyano groups coordinate to the metal atoms. 1c–4c are the first compounds with 3-cyanopyridine as a bridging ligand between two 3d M2+ ions. The bridges connect neighbouring [MIIBr2]n chains and this results in the formation of a wavy, two-dimensional network. All crystal structures were determined from X-ray powder diffraction data.^[1]

Preparation

In accordance with the following flow sheet, 3-cyano pyridine is prepared from 2-methylene glutaronitrile. 2-methyleneglutaronitrile (II), prepared by known methods, is reacted with a compound of the type RX where X is a halogen and R is either hydrogen or X. The reaction is a simple addition across a double bond forming III where R is X and V where R is H. III and V are treated with a Lewis acid in a cyclization reaction such that the nitrile group farthest from the halogen (X) and forming VI where R is H and VII where R is X. HR is eliminated from each of these compounds forming the desired 3-cyanopyridine. The elimination is car ried out by treatment with alkali in the case where R is equal to halogen and catalytically in the case where R is equal to hydrogen.^[2]

Hazard

3-Cyanopyridine has acute oral toxicity, it causes skin corrosion/irritation and serious eye damage/eye irritation.

References

[1]Ronald Harmetz, Dover, and Roger J. Tull, Metuchen, N.J., assignors to Merck & Co., Inc., Rahway, N.J. No Drawing. Filed Nov. 24, 1969, Ser. No. 879,519 at, C. C07d 31/46.

[2] HEINE M, FINK L, SCHMIDT M U. 3-Cyanopyridine as a bridging and terminal ligand in coordination polymers†[J]. CrystEngComm, 2018, 46: 7556-7566. DOI:10.1039/C8CE01568F.

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