Indium(III)-Catalysed [3+2] Annulation Reaction of Alkenes with α,β-Unsaturated Keto-Carboxylic Acid Derivatives for the Synthesis of γ-Butyrolactones

Herein, we report In(OTf)3 catalyzed (3+2) annulation reaction of an alkene with α,β-unsaturated keto-carboxylic acid for the synthesis of γ-butyrolactone derivatives. Furthermore, this [3+2] annulation reaction is also demonstrated with in situ generated iso-butylene and substituted α,β-unsaturated keto-carboxylic acid derivatives with broad substrate scope in very good yields. This expedient strategy selectively forms various C3-butyrolactone substituted oxindole derivatives in very good yield via simultaneous activation of electron rich and eletron poor alkene without formation of any other side products.