Q4(c). Fischer indole synthesis: 2-phenylindole
Discuss the mechanism of the reaction by writing the product.
[structure] → (ZnCl₂, HCl)
Answer in brief
Ene-hydrazine formation, [3,3]-sigmatropic shift, re-aromatisation, ring closure and loss of NH₃ convert acetophenone phenylhydrazone into 2-phenylindole .
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CoversFischer indole synthesis[3,3]-sigmatropic rearrangementene-hydrazineimine–enamine tautomerismrate-determining
All parts of Question 4
- 4(a) Enamine bromination with ring contraction; Dakin reaction10 marks
- 4(b) Claisen ester condensation: why R₂CHCO₂Et fails10 marks
- 4(c) Fischer indole synthesis: 2-phenylindole10 marks
- 4(d) Stabilised and unstabilised ylids; E/Z selectivity in the Wittig reaction10 marks