Yb(OTf)₃‐ or AuI‐Catalyzed Domino Intramolecular Hydroamination and Ring‐Opening of Sulfonamide‐Substituted 1,1‐Vinylidenecyclopropanediesters

Hard or soft determines the outcome: Five-membered N,O-heterocyclic compounds containing an alkyne moiety or a carbonyl group were efficiently synthesized from sulfonamide-substituted vinylidenecyclopropanediesters, catalyzed by a hard Lewis acid Yb(OTf)3 and a soft Lewis acid AuI complex, respectively (see scheme). The products were obtained in moderate to excellent yields under mild conditions and the reaction mechanisms were discussed on the basis of control and 18O-labeling experiments.