Rearrangement of 3-Alkyl-1-allylindoles: a model reaction for the biogenesis of echinulin-type compounds

Abstract

3-Alkyl-1-allylindoles (1) rearrange under acid catalysis to give the 2-substituted derivatives (2) and (3) with partial inversion of the migrating group (but-2-enyl, 3-methylbut-2-enyl). This represents a hitherto unobserved type of rearrangement, which may have both biogenetic and synthetic implications for echinuline-type compounds. The mechanism of the reaction has been proved to be intramolecular by a ‘cross-over’ experiment with deuteriated specimens.