The Fischer Indole Synthesis is a commonly used organic reaction, named after Hermann Emil Fischer, who discovered them in 1883. In the reaction, an indole, a heterocyclic aromatic compound, is formed from a (substituted) phenylhydrazine and an aldehyde or ketone. The reaction takes place in an acidic environment. Many medicines for migraine are synthesized in this way.
The choice of acid catalyst is important for the reaction. Brønde acids such as hydrochloric acid, sulfuric acid, polyphosphoric acids and p-toluenesulfonic acid are generally good catalysts. Lewis acids, such as boron trifluoride, zinc chloride, iron (III) chloride and aluminum chloride have already proven their services. Also see
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