Indium(III)-Catalyzed Cyclization of Aromatic 5-Enynamides: Facile Synthesis of 2-Aminonaphthalenes, 2-Amino-1H-indenes, and 2,3-Dihydro-1H-indeno[2,1-b]pyridines

Indium(III)-catalyzed cyclization reactions of aromatic 5-enynamides were studied. Indium triflate enabled the efficient synthesis of 2-aminonaphthalenes and 2-amino-1H-indenes from aromatic N-methyl-N-tosyl-ynamides bearing an ortho-vinyl and -isobutenyl group, respectively. The aromatic N-3-arylpropargylynamides bearing an ortho-gem-dihalovinyl subunit underwent a tandem cyclization/carbobromination reaction in the presence of indium tribromide to provide the dibrominated 2,3-dihydro-1H-indeno[2,1-b]pyridine derivatives in good yields.