The Fischer indole synthesis uses a protic or Lewis acid catalyst to convert a phenylhydrazine and an aldehyde or ketone to an indole. The phenylhydrazine makes an iminium ion with the carbonyl compound, which tautomerizes to the ene-hydrazine. A [3,3]-sigmatropic rearrangement disrupts the aromatic ring, but a subsequent proton transfer restores it. Cyclization (5-exo-trig), followed by loss of ammonia produces the indole system.

  • Reagents: Protic or Lewis Acid Catalyst
  • Reactant: Phenylhydrazine or Derivative, Aldehyde or Ketone
  • Product: Substituted Indole


Top Citations

Original Paper

Related Reactions

  • Gewald Reaction
  • Synthesis of Indoles

Related Compounds

  • Lewis Acid
  • Bronsted Acid
  • Aldehyde
  • Ketone
By shuhan yang


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