DBU-Promoted [3+2] Cycloaddition for the Synthesis of Trispiro Heterocycles from Acetylpyrazolyl-Substituted Oxindoles and Substituted Isatins

Stable and highly reactive 3-pyrazolyl oxindole derivatives have been developed as a novel three-carbon synthon, which undergo a formal [3+2] annulation with isatin promoted by non-nucleophilic base. This protocol provides a direct route for  the rapid construction of a novel class of 3,3’-polyspiro oxindole-γ-butyrolactone scaffolds. These polyspiro frameworks are recognized as privileged scaffolds for a wide range of bioactive compounds. The developed protocol features mild reaction conditions, a broad substrate scope, and scalability.