Ruthenium-Catalysed Isomerisation of Allylhydrazines: A New Entry to the Fischer Indole Synthesis

The synthesis of non-symmetrically substituted allyl phenylhydrazines and their isomerisation to the corresponding enehydrazines is reported. The isomerisation is triggered by a combination of Grubbs' first-generation catalyst and LiBEt3F1. Indoles are formed directly from the enehydrazines by the Fischer indole synthesis under the reaction conditions.