Rhenium-catalyzed synthesis of indene derivatives via C–H bond activation*

Rhenium complex, [ReBr(CO)3(thf)]2-catalyzed reactions between aromatic imines and either acetylenes or α,β-unsaturated carbonyl compounds gave indene derivatives in good to excellent yields. These reactions proceed via C–H bond activation, insertion of acetylenes or α,β-unsaturated carbonyl compounds, intramolecular nucleophilic cyclization, and reductive elimination. Indene derivatives were also obtained from aromatic ketones and α,β-unsaturated carbonyl compounds in the presence of catalytic amounts of the rhenium complex and p-anisidine. Sequential ruthenium-catalyzed hydroamination of aromatic acetylenes with anilines, and rhenium-catalyzed reactions of the formed aromatic ketimines with α,β-unsaturated carbonyl compounds also provided indene derivatives.