Heterocycles

Heterocycles represent a larger group of organic compounds and play an important role in all aspects of pure and applied chemistry. Currently, chlorinated heterocyclic compounds can be found among potent pharmaceuticals, crop protection agents, and products of technical importance.

Pentachloropyridine

Pentachloropyridine is a perhalogenated heterocyclic compound with the chemical formula C5Cl5N. It is a white to off-white Flake. It is a potentially excellent scaffold because they are highly reactive toward nucleophilic attack as a result of its electron-deficient nature, and in principle, all halogen atoms may be displaced by nucleophile.

Synthesis and functionalized

The first realistic and readily scaled synthesis of pentachloropyridine was reported by Kekule. In addition, commercially available pentachloropyridine and its derivatives can be further functionalized by Sell and Dootson. Another commonly used method of functionalization of pentachloropyridine is to heat a pyridine mixture at 250°C and use excess phosphorus pentachloride, which can form a mixture. But its total yield is low.

Reaction properties

Differentiation reactivity of perchlorinated heteroaromatic compounds toward nucleophiles was achieved by substitution at 2-, 3-, and 4-positions of pyridine. In general rule, reactions of nucleophiles with pentachloropyridine occur almost exclusively to give products arising from ortho and para to ring nitrogen in which bulky nucleophiles are more likely to attack the less hindered 2-position, while small nucleophiles substitute the 4-position. It is able to synthesize a variety of compounds through nucleophilic substitution reactions, such as reactions with N?centered nucleophiles, O?center nucleophiles, O and N bidentate nucleophiles, organolithium compounds, etc., and is also capable of synthesizing polychlorobipyridines which is the organic heterocyclic compound used prominently in many areas of chemistry and common precursors to many derivatives. Perchloropyridines represent an extremely interesting class of organic compounds that can be utilized as precursors and building blocks for the synthesis of a wide range of substituted heterocyclic compounds.

References

[1] Ranjbar-Karimi R, et al. Utility of pentachloropyridine in organic synthesis. Journal of the Iranian Chemical Society, 2020; 17: 2145–2178. 

[2] Moradi T, et al. Site reactivity of indole derivatives with pentachloropyridine. Polycyclic Aromatic Compounds, 2020; 42: 1610-1619. 

[3] Ager E, et al. Photolysis of pentachloropyridine and pentachloropyridine 1-oxide. Journal of the Chemical Society, Chemical Communications, 1972; 505-506.