TfOH-Catalyzed Reactions of Aryl Methyl Ketones with Ynamides: Synthesis of 1-Amino-1 H -indenes and 2,4-Dienamides.

The efficient synthesis of 1-amino-1 H -indenes and 2,4-dienamides was realized via TfOH-catalyzed reactions of aryl methyl ketones with terminal ynamides in two distinct pathways. Aromatic ketones with high electrophilicity underwent [3 + 2] annulation with ynamides to produce 1-amino-1 H -indenes, while aromatic ketones with low electrophilicity proceeded under the same conditions to afford 2,4-dienamides. Furthermore, the obtained 1-amino-1 H -indenes could be converted into the corresponding 1 H -indenes and dihydro-1 H -indenes in excellent yields.