Tandem Au-Catalyzed 3,3-Rearrangement−2 + 2 Cycloadditions of Propargylic Esters:  Expeditious Access to Highly Functionalized 2,3-Indoline-Fused Cyclobutanes

The treatment of readily available propargylic indole-3-acetates with a catalytic amount of AuCl(PPh3)/AgSbF6 leads to tandem activations of the propargylic esters and the in situ generated allenylic esters, resulting in expeditious access to highly functionalized cyclobutanes with fused 2,3-indoline and gamma-lactone rings and an exocyclic E-double bond through sequential 3,3-rearrangement and 2 + 2 cyclization.