Stereoselective Synthesis of Spirocyclic Indolin-3-ones through a Gold(I)-Catalyzed Cascade Cyclization of Azido-alkynes

Herein, we describe a gold(I)-catalyzed synthesis of spirocyclic indoline-3-ones, a motif found in numerous biologically active natural products. The reaction proceeds through the addition of an oxygen nucleophile to an α-imino gold carbene, which is generated by a gold(I)-catalyzed cyclization of an azido-alkyne, followed by spirocyclization. Notably, the spirocyclization step proceeds stereoselectively to give 2-(hydroxymethyl)-C2-spirocyclic indolin-3-ones as the sole isolable stereoisomer. The reaction has a good substrate scope, affording a variety of indoline-3-ones in satisfactory yields.