Five Membered Heterocyclic Compounds
Furan, Thiophene, Pyrrole and their derivatives are all highly activated compared to benzene. These compounds all contain an atom with an unshared pair of electrons (oxygen, sulphur, or nitrogen) as a member of the aromatic ring, which substantially increases the stability of the cationic intermediate. Examples of electrophilic substitutions to pyrrole are the Pictet-Spengler reaction and the Bischler-Napieralski reaction.
Read more about this topic: Electrophilic Aromatic Substitution
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