Photoinduced radical-polar crossover cyclization reactions

Cyclization reactions provide an instant and effective path to generate mono- and polycyclic systems and are one of the most important and fundamental fields in organic chemistry. Catalytic transformations involving photoinduced radical-polar crossover cyclization (RPCC) have become highly valuable and powerful processes for transforming simple and readily available alkene precursors into structurally complex cyclic molecular scaffolds; especially, C–X unsaturated bond net-neutral RPCC, in which both the single-electron oxidation and reduction steps occur through interaction with the photocatalyst and without the addition of exogenous oxidants or reductants, is undergoing rapid development. This review will summarize the latest advances in the photoinduced RPCC reactions (only redox-neutral and oxidant/reductant-free transformations were taken into closer consideration) and aims to give an overview of the different existing strategies based on alkene RPCC to photocatalytically build cyclic architectures from radicals and carbon-centered anions or equivalents of those.