Indium-Catalyzed [1+n] Annulation Reaction between β-Ketoester and α,ω-Diyne

A catalytic amount of In(NTf(2))(3) effects the inter- and intramolecular addition of a beta-ketoester to an alpha,omega-diyne to produce a 1,3-dimethylenecycloalkane derivative in a single step. This [1 + n] annulation reaction shows good functional group tolerance and allows the synthesis of five-to seven-membered carbo- and heterocyclic as well as spirocyclic structures in moderate to excellent yields.