Harnessing Strain-Release via Photocatalysis to Construct Functionalized Spirocyclobutyl Oxindoles

Bicyclo[1.1.0]butanes have attracted significant attention from synthetic chemists for their strain-release functionalization, enabling access to complex molecular architectures. This study demonstrates a photocatalyzed, strain-release-driven radical cyclization for efficiently synthesizing heteroarylated spirocyclobutyl oxindoles. By strategically incorporating redox-active functionalities into the substrate design, we achieve an unusual/reverse mode of reactivity in bicyclo[1.1.0]butanes (BCB). This approach enables the broad and efficient installation of diverse heterocycles onto spirocyclobutyl oxindoles under mild, operationally simple conditions, making it suitable for the late-stage functionalization of drug-like molecules.