Abstract:
A method to prepare 3-substituted-2-formyl indole derivatives from N-Boc o-aminoarylketones and ethoxyacetylene through a cascade of reactions in a single operation that included a metal/catalyst free nucleophile triggered 5-exo-dig cyclization and acid mediated 1,3-allyl alcohol isomerization (1,3-AAI) is described. A variety of aryl, vinyl and alkynyl groups are introduced at C3 of indole-2-carboxaldehyde while having a high functional group compatibility. The 3-alkynyl adducts, which are highly valuable substrates for diversity oriented synthesis, are further transformed to useful carboline and carbazole derivatives through novel pathways.
