Construction of polysubstituted spiro[2.3] or [3.3] cyclic frameworks fused with a tosylated pyrrolidine promoted by visible-light-induced photosensitization

Herein, we presented a visible-light-induced intramolecular [2 + 2] cycloaddition of methylenecyclopropanes (MCPs) in the presence of a polypyridyl iridium(III) catalyst for the rapid construction of polysubstituted spiro[2.3] or [3.3] cyclic frameworks fused with a tosylated pyrrolidine in good yields under mild conditions. This newly developed photochemical protocol demonstrates a broad scope on the preparation of spirocyclic skeletons including diversified multi-spiral compounds containing dispiro[2.0.24.23] and dispiro[2.0.34.23] frameworks that might be useful in the synthesis of drug like molecules or the other functional materials. The mechanistic paradigm has been investigated on the basis of fluorescence emission quenching analysis, CV measurement and the control experiments, indicating that this visible-light photoinduced [2 + 2] cycloaddition proceeded through a triplet excited state.