Plancher rearrangement

What is Plancher rearrangement?

The Plancher rearrangement involves the migration of an alkyl or aryl group from position 2 to position 3 of indolenines or vice versa. This results in the formation of compounds that originate from a more stable carbocation intermediate.

Plancher rearrangement - general reaction scheme
Plancher rearrangement
Plancher rearrangement - general reaction scheme
Plancher rearrangement

R1, R2= alkyl, aryl (see list of acronyms)

Due to its discovery by Plancher in 1896, the reaction is named after him and is commonly referred to as the Plancher rearrangement. The rearrangement is influenced by both the migratory aptitude of the group and the thermodynamic stability of the product. However, the Plancher rearrangement typically does not occur at room temperature.

References

Ciamician, G. and Plancher, G. (1896), Ueber die Einwirkung von Jodäthyl auf α-Methylindol (Methylketol). [On the effect of iodoethyl on α-methylindole (methyl ketol).] Ber. Dtsch. Chem. Ges., 29: 2475-2482. https://doi.org/10.1002/cber.18960290318

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