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Heterocyclic Ring

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A heterocyclic compound is a cyclic compound that has atoms of at least two different elements as members of its ring(s). The counterparts of heterocyclic compounds are homocyclic compounds, the rings of which are made of a single element.

Although heterocyclic compounds may be inorganic, most contain at least one carbon atom, and one or more atoms of elements other than carbon within the ring structure, such as sulfur, oxygen, or nitrogen.

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Classification based on electronic structure

5-Membered rings 6-Membered rings

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5-Membered rings i.e – Furan, Thiphene, Pyrrole 6-Membered rings i.e – Pyridine, Pyran

Benzofused rign i.e – Indole ring, Quinoline ring

etc

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With heterocycles containing five atoms, the unsaturated compounds are frequently more stable because of aromaticity.

i.e - Puran,, Pyrrole,Thiphene etc

Puran, It is an aromatic compound. Because it has Resonance structure.

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Pyrrole ring

It is also a aromatic compound.

It show aromaticity in its structure.

Synthesis of Pyrrole:

Pyrrole can be synthesized from mucic acid Acetylene Paal-knorr synthesis Succinamide Furan etc

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Pyrole ring is acidic. Pyrrol donate proton in reaction for this

reason,it is acidic in nature.

Chemical Reaction of Pyrrole . It gives Electrophilic substitution

reaction

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Six-membered rings with a single heteroatom

i.e – Pyridine

Synthesis of pyridine:

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Chemical reaction of Pyridine -Electrophilic Substitution reaction of

pyridine.

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Benzofuse ring such as Indole ring, Quinoline ring, Isoquinoline ring.

Indole synthesis

Leigngruber-Batcho indole synthesis Fisher indole synthesis

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Electrophilic Substitution reaction

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Oxidation of indole Due to the electron-rich nature of

indole, it is easily oxidized. Simple oxidants such as N-bromosuccinimide will selectively oxidize indole 1 to oxindole (4 and 5).

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Halogenation reaction of Isoquinoline

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