Synthesis of Spiro3,3′-Cyclopropyl Oxindolesvia Cyclopropanation of 3‑Alkenyl-oxindoles with CF₃‑Imidoyl Sulfoxonium Ylides

A catalyst and additive-free [2+1] annulation of 3-alkenyl-oxindoles with CF₃-imidoyl sulfoxonium ylides (TFISYs) for the construction of spiro 3,3′-cyclopropyl oxindoles has been achieved. A cascade intermolecular Micheal-addition reaction and intramolecular nucleophilic substitution sequence might be involved in the transformation, which afforded a wide range of multisubstituted spiro 3,3′-cyclopropyl oxindole products with high efficiency and diastereoselectivity.