Abstract
| - Aryl-2-(N-methyl/benzyl-3-indolyl)cyclopropyl ketones 2a−m are shown to undergo a novel unexpected domino carbocationic rearrangement in the presence of SnCl4/CH3NO2 yielding 2-aroyl-3-aryl-1H-cyclopenta[c]carbazoles3a−m in good yields. The possible mechanistic pathway forthis interesting transformation involves a series of cascadeevents, (a) electrophilic ring opening of cyclopropyl ketone,(b) intermolecular enol capture of the resulting zwitterionicintermediate, (c) electrophilic dimerization of indole moietiesto give tetrahydrocarbazole intermediate and its subsequentaromatization by elimination of an indole moiety and dehydrogenation, and (d) intramolecular aldol condensation ofthe side chain to give a cyclopentene ring. The overall transformation involves formation of three carbon−carbon bondsalong with a fused benzene and a substituted cyclopentenering in one-pot operation from simple indole precursors.
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