Five-Membered Heterocycles Fused to One Benzene Ring

Five-Membered Heterocycles Fused to One Benzene Ring... 

FIVE-MEMBERED HETEROCYCLES FUSED TO ONE BENZENE RING... 

The fusion of a benzene ring to the 2,3-positions of a pyrrole generates one of the most important heterocyclic ring systems - indole. This chapter develops a description of the chemistry of indole, then discusses modifications necessary to rationalise the chemistry of the benzo[ )]furan and benzo[ >]thiophene analogues. Finally, the trio of heterocycles in which the benzene ring is fused at the five-membered ring 3,4-positions are considered. 

Firefly luciferin is an example of an azole that contains a benzene ring fused to the five-membered ring. Such structures are fairly common. Another example is benzimidazole, present as a structural unit in vitamin B12. Some compounds related to benzimidazole include purine and its amino-substituted derivative adenine, one of the so-called heterocyclic bases found in DNA and RNA (Chapter 28). 

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