Palladium(II)/Copper Halide/Solvent Combination for Selective Intramolecular Domino Reactions of Indolecarboxylic Acid Allyl-amides: An Unprecedented Arylation/Esterification Sequence

摘要

Intramolecular oxidative palladium-catalyzed reactions of indolylallylamides in the presence of the couple bis(acetonitrile) palladium dichloride and copper(II) halide are described. Starting from 2-and 3-indolylallylamides and involving in both cases the C-3 position of the indole nucleus, variously substituted β-carbolinones were obtained by arylation/ halogenation, arylation/esterification or arylation/ carboalkoxylation processes. On the other hand, an unusual aminohalogenation/halogenation sequence performed on 2-indolylallylamides gave rise topyrazino[1,2-a]indole products. The carboesterifica-tion process is the result of an unknown path that involves the DMF or DMA used as solvent. The outcome of the reactions of the 3-indolylallylamides arises from a totally selective 1,2-migration of the acyl group on the supposed spiro intermediates formed from the nucleophilic attack of the C-3 indole position.