Fischer indolisation of 2,6-dialkyl and 2,4,6-trialkylphenylhydrazones of diketones and ketoesters

Unlike the migration of a methyl group observed in the ZnCl2 or acetic acid-catalysed indolisation of phenylhydrazones, dry ethanolic HCl catalysed indolisation of 2,6-dimethyl- and 2,4,6-trimethylphenylhydrazones of various substituted butane-2,3-diones and ethyl pyruvates yields 7-methyl- and 5,7-dimethyl-3-substituted indoles indicating elimination of an ortho-methyl group during indolisation.