Photoredox Catalysis in Organic Synthesis and Transformations

Photoredox catalysis has emerged as a transformative approach in organic chemistry, harnessing visible light to mediate electron‐transfer events and generate reactive radical species under mild conditions. By judicious selection of photocatalysts—ranging from transition‐metal complexes to organic dyes—chemists can orchestrate single‐electron transfer cycles that activate strong bonds, induce selective oxidations or reductions and drive cross‐coupling, deoxygenation and C–H functionalisation processes. Recent advances have expanded the substrate scope to include unactivated alkenes, aromatic carboxylic acids and simple alkyl halides, while the integration of chiral co‐catalysts has enabled enantioselective variants of classical transformations. The inherently green nature of photoredox protocols—employing visible light rather than stoichiometric reagents—has fostered applications in late‐stage functionalisation of complex molecules, pharmaceutical synthesis and the sustainable valorisation of biomass‐derived feedstocks. As mechanistic understanding deepens through actinometry and intermittent illumination studies, photoredox catalysis is poised to deliver ever more selective, energy‐efficient and scalable routes for the construction of C–C, C–N, C–O and C–S bonds.

Research from Nature Portfolio

Recent studies have showcased the power of photoredox methods to achieve deoxygenative coupling of aromatic acids with alkenes in aqueous media, delivering structurally diverse ketones from simple feedstocks. This strategy employs visible light to generate acyl radicals beyond conventional redox limits, enabling concise syntheses of macrocycles and active pharmaceutical targets. In parallel, innovations in asymmetric photoredox radical coupling have realized formal enantioconvergent substitution of racemic alkyl halides, uniting alkyl and amino radicals under the influence of chiral Brønsted acids to afford enantiomerically enriched β-amino ketones and quaternary stereocentres. More broadly, the drive for sustainability has led to a portfolio of photoredox‐driven processes that mimic natural photosynthesis, offering greener routes for industry and academia by minimising waste and harnessing ambient light sources.

Photoredox Catalysis in Organic Synthesis and Transformations publication trend

The graph below shows the total number of articles in photoredox catalysis in organic synthesis and transformations across all publications each year (not limited to Nature Index journals).

Technical terms

Photoredox catalysis: A strategy that uses light‐absorbing catalysts to induce single‐electron transfer, generating radical ions for subsequent bond‐forming reactions.

Single‐electron transfer (SET): The process in which one electron is transferred between reactants or between a catalyst and substrate during a photoredox cycle.

Radical intermediate: Short‐lived, open‐shell species bearing an unpaired electron, which can engage in diverse bond‐forming or bond‐breaking events.

Enantioconvergent substitution: A transformation in which both enantiomers of a racemic electrophile are converted into a single enantiomer of a product under catalytic conditions.

Reductive radical–polar crossover: A mechanism that transitions from a radical pathway to a polar reaction manifold, enabling the use of conventional electrophiles in radical additions.

References

1. Synthetic Photoelectrochemistry. Angewandte Chemie International Edition (2020).
2. Recent advances in visible light-activated radical coupling reactions triggered by (i) ruthenium, (ii) iridium and (iii) organic photoredox agents. Chemical Society Reviews (2021).
3. A general deoxygenation approach for synthesis of ketones from aromatic carboxylic acids and alkenes. Nature Communications (2018).
4. Chemistry glows green with photoredox catalysis. Nature Communications (2020).
5. Reductive radical-polar crossover: traditional electrophiles in modern radical reactions. Chemical Science (2019).
6. Metal-free, visible-light-mediated, decarboxylative alkylation of biomass-derived compounds. Green Chemistry (2016).
7. Formal enantioconvergent substitution of alkyl halides via catalytic asymmetric photoredox radical coupling. Nature Communications (2018).
8. Visible-Light Actinometry and Intermittent Illumination as Convenient Tools to Study Ru(bpy)3Cl2 Mediated Photoredox Transformations. Scientific Reports (2015).