Indium-Catalyzed Synthesis of Furans and Pyrroles via Cyclization of α-Propargyl-β-keto Esters

In(OTf)(3) or In(NTf2)(3) effectively catalyze the cycloisomerization reaction of alpha-propargyl-beta-keto esters and their imine analogues to afford trisubstituted furans and pyrroles, respectively. Both terminal and internal alkynes take part in the reaction with good functional-group compatibility in the presence of only a small amount of the catalyst.