Spiro­[indoline-3,4′-piperidine] is a significant structural scaffold in numerous polycyclic indole alkaloids with a variety of bioactivities. In this study, a synthetic strategy was developed to access spiro­[indoline-3,4′-pyridin]-2-yl carbamate via an AgOTf/PPh3-catalyzed tandem cyclization of tryptamine-ynesulfonamides. The unique feature of this strategy is the efficient intermolecular capturing of the in situ generated spiroindoleninium intermediates with carbamates, leading to the diastereoselective syntheses of spiro­[indoline-3,4′-pyridin]-2-yl carbamate derivatives. A broad scope of this cyclization was demonstrated by a variety of tryptamine-ynesulfonamide substrates and several carbamates. A plausible mechanism of this reaction was proposed.

N‐Fluorobenzenesulfonimide (NFSI), one of the most popular fluorinating agents in organic synthesis, was used as a ligand of silver triflate (AgOTf) to assist the trapping of the persistent spiroindoleninium intermediates by forming a weak noncovalent interaction between the substrate and metal ligand. The AgOTf/NFSI catalytic system was identified in the cycloisomerization of tryptamine‐ynamide to spiro[indoline‐3,4′‐piperidine] derivatives. The substrate tolerances were demonstrated by various synthetic substrates and commercially available nucleophiles. A cation‐π‐π model was proposed to elucidate the mechanism of action based on the experimental observations and density functional theory (DFT) calculations.