Heterocyclic chemistry

More than half of all known organic compounds and most drugs contain a heterocycle, a ring with some atom other than carbon. Aromatic heterocycles are found in nucleic acids, haem, chlorophyll, vitamins, alkaloids and dyes.

This topic covers the reactivity of the π-excessive five-membered heterocycles (pyrrole, furan and thiophene) and the π-deficient six-membered ones (pyridine), that of heterocycles fused to benzene (indole and quinoline) and the great classical syntheses of heteroaromatic rings: Paal–Knorr, Hantzsch and Fischer.