Radical Cyclization Techniques in Organic Synthesis

Radical cyclization has emerged as a powerful strategy for constructing diverse ring systems under mild conditions. By generating reactive radical intermediates that undergo intramolecular bond formation, this approach enables the rapid assembly of carbocycles and heterocycles with high levels of regiocontrol and stereocontrol. Traditional methods employ oxidants or radical initiators such as manganese(III) acetate to abstract hydrogens or to activate 1,3-dicarbonyl precursors, while more recent developments harness photoredox catalysis and metal‐free radical generators. These innovations have expanded substrate scope to include spirocyclic frameworks, fused bicycles and densely substituted heterocycles. Radical cyclization techniques are valued for their operational simplicity, tolerance of functional groups and capacity to streamline multistep syntheses of natural products and pharmaceuticals. Advances in catalyst design and mechanistic understanding have enabled unprecedented selectivities, facilitating late-stage diversification and enabling scalable access to bioactive scaffolds. As a result, radical cyclizations now play a central role in the modular construction of complex molecular architectures with global impact in medicinal chemistry, agrochemistry and materials science.

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Radical Cyclization Techniques in Organic Synthesis publication trend

The graph below shows the total number of articles in radical cyclization techniques in organic synthesis across all publications each year (not limited to Nature Index journals).

Technical terms

Radical cyclization: Intramolecular ring formation via a carbon-centred radical intermediate.

Oxidative radical cyclization: Generation of radical intermediates through an oxidation step, often using metal oxidants.

Regioselectivity: Preference for reaction at one position over others in a multifunctional substrate.

Stereoselectivity: Preference for formation of one stereoisomer when multiple are possible.

Spirocycle: A bicyclic system in which two rings share a single atom (the spiro centre).

References

1. Recent Advances in Manganese(III)-Assisted Radical Cyclization for the Synthesis of Natural Products: A Comprehensive Review. Molecules (2024).
2. Facile Access to Highly-Substituted Dihydrofurans Using Resonated Vinylpentanedione Radicals Generated by Mn(III)-Based Oxidation. Heterocycles (2021).
3. A Short Synthesis of Aphanamol I in Both Racemic and Enantiopure Forms. Chemistry - A European Journal (2016).