Indium-catalyzed [1 + n] annulation reaction between beta-ketoester and alpha,omega-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.