Base-Mediated Tandem Michael Addition and SuFEx Cyclization for the Synthesis of Sultone-Containing Spirooxindoles

Sulfur-containing spirooxindoles are recognized for their significant biological activity, yet accessing these compounds with diverse heteroatoms in the spirocyclic core has remained challenging. This study introduces a simple and efficient base-mediated tandem Michael addition reaction and SuFEx cyclization to synthesize novel sultone-containing spirooxindoles. The transformation occurred in a green solvent, which proved essential in suppressing side reactions, leading to the successful synthesis of 20 novel sultone-spirooxindoles and two sulfonates that are resistant to cyclization. Additionally, a chiral variant of the reaction was explored, laying the groundwork for the future development of enantioselective methods.