Radicalcatalytic

Radicalcatalytic refers to catalytic processes in which radical intermediates are central to the catalytic cycle. In radicalcatalytic systems, a catalyst promotes the formation of radical species that participate in bond-forming steps and are regenerated to complete the catalytic cycle. The concept encompasses both metal- and organocatalytic approaches and is frequently associated with photoredox and radical-relay strategies, where light or redox chemistry generates radicals under mild conditions.

Mechanistically, radicalcatalysis often proceeds by initiation to generate one or more radicals, followed by propagation steps in which the substrate undergoes radical addition, abstraction, or coupling to form product and new radical species. The active catalytic species may be a metal complex capable of single-electron transfer, an organic photocatalyst, or a small-molecule mediator. The key feature is that electron transfer and radical intermediates, rather than two-electron processes alone, drive the transformation.

Common platforms include photoredox-catalyzed reactions, nickel- and copper-catalyzed radical couplings, and organocatalytic radical relay cycles. Applications span C–C and C–heteroatom bond formation, hydrofunctionalization, decarboxylative couplings, and late-stage functionalization, often enabling mild temperatures and broad functional-group tolerance.

Challenges include achieving selectivity among competing radical pathways, controlling chain processes to prevent termination or side reactions, and ensuring robust catalyst turnover and scalability. Ongoing research aims to broaden substrate scope, improve efficiency, develop sustainable catalysts, and integrate radicalcatalytic strategies with other catalytic paradigms.