Photoinduced [3+2] cycloaddition <i>via</i> HFIP-promoted <i>in situ</i> formation of isobutylene from the Boc group

We herein report an HFIP-promoted, photoinduced [3+2] cycloaddition between carbonyl cyclopropanes and <i>in situ</i> generated isobutylene, which enables access to diverse polysubstituted cyclopentane and pyrrolidine derivatives. Mild conditions, simple operation and excellent functional group tolerance characterize this protocol. Above all, it not only eliminates the hazards linked with the storage and handling of pressurized isobutylene but also highlights the versatility of the Boc group as a synthon in complex molecule assembly, providing a strategic advance toward greener and more sustainable synthetic methodologies.