Foscarnet is an antiviral drug with an unusual chemical structure and an important clinical role. Unlike many medicines that must be converted inside cells into an active form, foscarnet directly interferes with viral DNA polymerases and reverse transcriptases, enzymes that viruses need to copy their genetic material. Its phosphate-like structure enables it to interact with the catalytic machinery of these enzymes, helping block the extension of newly synthesized viral DNA. The drug is especially valuable in situations involving viral infections that have become resistant to other treatments, including certain cytomegalovirus and herpesvirus infections. Yet the same phosphorus-rich chemistry that gives foscarnet its biological activity also complicates its preparation. Producing the molecule requires precise control over carbon–phosphorus and oxygen-rich functional groups, and conventional routes can involve multiple steps, carefully selected reagents and waste-generating transformations. The possibility of building foscarnet electrochemically from carbon dioxide and phosphite is therefore significant not simply because it uses a different reactor, but because it proposes a more direct way to assemble a medically valuable compound from abundant, relatively inexpensive starting materials.

Carbon dioxide is chemically stable, which is one reason it accumulates in the atmosphere and another reason it is difficult to use as a raw material. To convert CO₂ into a useful organic or inorganic product, chemists must first activate it by adding electrons, often creating a highly reactive intermediate known as the carbon dioxide radical anion, CO₂·⁻. This species has an unpaired electron and can participate in bond-forming reactions that ordinary carbon dioxide cannot. Electrochemistry offers a way to generate such intermediates at an electrode, using electrical current rather than a separate chemical reducing agent. But the radical anion is also fleeting and can follow many competing pathways, including reactions that return it to carbon dioxide or convert it into unwanted products such as carbon monoxide, formate or oxalate. The central problem is thus not merely making CO₂·⁻, but producing it at the right rate and bringing it into contact with the correct reaction partner before it disappears. In this study, that partner is a phosphite-derived radical species, written as PO₃·²⁻, whose encounter with activated carbon dioxide leads toward the phosphorus-containing framework of foscarnet.

The researchers addressed the problem by modifying bismuth with an ionic liquid. Bismuth is already known as a useful electrocatalyst for carbon dioxide reduction because it can promote selective transformations while avoiding some of the hydrogen evolution and hydrocarbon-forming reactions associated with other electrode materials. On its own, however, bismuth did not produce foscarnet at the same rate. The ionic liquid changes the microscopic environment around the catalyst and the dissolved reactants. Ionic liquids are salts that remain liquid at relatively low temperatures, and their charged, highly tunable structures can influence solvent organization, ion transport, adsorption and electron-transfer reactions. According to the mechanistic analysis, the ionic liquid in IL@Bi participates in radical-mediated electron transfer, enhancing the generation of CO₂·⁻ in the electrolyte rather than leaving the electrode to carry out the entire activation process directly. This distinction matters because the reaction is controlled not only by the electrode’s composition, but also by what happens in the thin liquid layer surrounding it. By creating a more favorable interfacial environment, IL@Bi increases the supply of activated carbon dioxide available for the next bond-forming step.

The proposed mechanism then brings the two radical intermediates together. Phosphite, a lower-oxidation-state phosphorus compound, can be converted under electrochemical conditions into the phosphite radical PO₃·²⁻. The ionic-liquid-modified surface helps facilitate an encounter between this species and CO₂·⁻, allowing the carbon component from carbon dioxide to become connected to the phosphorus-containing component. Subsequent electron-transfer and proton-transfer steps can then produce the oxygen-rich structure associated with foscarnet. The importance of the ionic liquid is therefore twofold: it promotes the formation of carbon dioxide radicals and helps organize or accelerate their reaction with phosphite radicals. This is a form of reaction control that operates through local molecular encounters. Instead of treating the electrolyte as an inert medium through which current merely flows, the study presents it as an active chemical participant in steering reactive intermediates toward the desired product. Such control is especially valuable in radical chemistry, where small changes in concentration, charge distribution or diffusion distance can determine whether a useful coupling occurs or the intermediates are lost to side reactions.

The performance figures provide a quantitative measure of the advance. Faradaic efficiency describes the fraction of electrical charge that is used to form the target product rather than driving competing reactions. A value of 37.5 percent means that more than one-third of the electrons passed through the electrochemical system contributed, on the reported basis, to foscarnet formation. The current density of 224.2 milliamperes per square centimetre indicates how much electrical current the electrode can sustain per unit area while operating in the process. High current density is important for practical electrochemical manufacturing because it can allow more product to be made from a smaller electrode, although efficiency, stability, separation and energy consumption must also be considered when judging industrial potential. The reported production rate—1,555.6 micromoles per square centimetre per hour—was ten times that achieved with unmodified bismuth. Together, these measurements show that the ionic-liquid modification substantially improves throughput, not merely the detectability of a previously inaccessible product. They also establish a benchmark for future work aimed at raising selectivity and converting more of the electrical input into foscarnet.

The study is part of a broader effort to transform carbon dioxide from an emissions problem into a feedstock for valuable chemicals. Electrochemical manufacturing can, in principle, be powered by renewable electricity and can replace some stoichiometric reducing or oxidizing reagents used in conventional synthesis. That does not automatically make every electrochemical process sustainable: the overall environmental profile depends on the source of electricity, the lifetime and manufacture of the catalyst, the identity and recovery of the electrolyte, solvent use, product purification and the fate of unreacted feedstocks. Ionic liquids can be advantageous because they have low volatility and tunable properties, but their production, recycling and possible environmental release also require assessment. Likewise, phosphite is a useful phosphorus source, yet the complete material and energy balance of the process will determine whether it offers a meaningful advantage at manufacturing scale. The new results nevertheless provide a compelling proof of concept: carbon dioxide can be incorporated into a clinically relevant phosphorus-containing molecule through a carefully engineered electrochemical radical-coupling pathway rather than being treated solely as an inert by-product.

The researchers’ findings could influence both pharmaceutical synthesis and catalyst design, but several steps remain before the method can be considered a replacement for established production routes. Long-duration operation will need to show that the IL@Bi catalyst retains its activity and that the ionic liquid does not leach, degrade or become contaminated by reaction products. The process must also be tested with respect to product isolation, purity, water and energy requirements, electrode fabrication and operation at larger scales. A laboratory current density and production rate are promising indicators, but scale-up can change mass transport, heat management and the distribution of reactive intermediates across the electrode. Further improvements in Faradaic efficiency could reduce electrical waste and simplify downstream purification. Even with those challenges, the work demonstrates a striking chemical possibility: a greenhouse gas and an inorganic phosphorus compound can be joined through electricity to make an important antiviral drug. By using an ionic liquid to mediate radical formation and pairing it with a bismuth catalyst, the researchers have shown how the boundaries between electrode, electrolyte and reactant can be deliberately blurred to create new routes to valuable medicines.

Subject of Research: Electrochemical synthesis of the antiviral drug foscarnet by coupling carbon dioxide and phosphite using an ionic-liquid-modified bismuth catalyst

Article Title: Electrochemical coupling of CO₂ and phosphite for foscarnet synthesis

Article References: Wang, H., Duan, R., Wang, Y. et al. “Electrochemical coupling of CO₂ and phosphite for foscarnet synthesis.” Nature Catalysis (2026). https://doi.org/10.1038/s41929-026-01608-6

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41929-026-01608-6

Keywords: foscarnet synthesis, carbon dioxide utilization, electrochemical catalysis, ionic-liquid-modified bismuth, phosphite coupling, antiviral drugs, radical-mediated electron transfer, sustainable chemistry

Published on March 12, 2026, in the esteemed journal Nature Synthesis, the study introduces what is described as an “anti-Friedel–Crafts” reaction, flipping the classic Friedel–Crafts approach on its head. Traditional Friedel–Crafts reactions rely on the use of strong acids or metal catalysts under harsh conditions, necessitating their application early in drug manufacturing. These reactions often require lengthy and complex multistep syntheses to reach the final drug molecule. The Cambridge team’s approach allows key modifications to be made at a much advanced stage, sparing chemists the laborious dismantling and rebuilding of complex molecular frameworks.

At the heart of this new chemistry lies a photoinitiated process powered solely by visible light from an LED source—eliminating the reliance on heavy metals or forcing reagents often linked to environmental and toxicological concerns. By operating at ambient temperature and pressure, the reaction triggers a chain mechanism that selectively creates carbon–carbon bonds with high functional-group tolerance. This selectivity means sensitive functionalities present in the molecule remain intact throughout the reaction, a crucial feature for late-stage functionalization in medicinal chemistry.

David Vahey, the first author of the study and a PhD candidate at St John’s College, Cambridge, emphasizes the practical implications of this finding. Drug discovery traditionally involves painstakingly reconstructing whole molecular regions just to evaluate the impact of subtle modifications. With this method, scientists can instead modify “hit” compounds directly, rapidly exploring a variety of structural analogs without the overhead of complete resynthesis. This capability promises to speed up the iterative process of medicinal chemistry, a bottleneck that often stifles drug innovation and increases costs.

The environmental benefits are equally compelling. Conventional synthetic routes consume large quantities of hazardous reagents and energy, generating substantial chemical waste. This photon-driven chemistry markedly reduces reagent requirements and energy inputs, aligning seamlessly with the pharmaceutical industry’s increasing commitment to sustainability. Given the global push to lower the environmental footprint of drug manufacturing, such advancements have the potential to usher in greener, cleaner pharmaceutical production practices on a large scale.

Professor Erwin Reisner, senior author and a leading figure in the field of sustainable chemistry and energy at Cambridge, highlights the importance of expanding the toolbox of synthetic chemists with mild yet powerful methods. His group’s legacy, heavily inspired by nature’s photosynthesis, aims to turn sunlight into a practical energy source for chemical transformations. This latest discovery leverages that ethos by coupling light energy with a radical, metal-free reaction pathway for carbon–carbon bond formation, a cornerstone reaction in organic chemistry.

One of the most fascinating aspects of this discovery is its serendipitous origin. The breakthrough emerged unexpectedly during a “failed” control experiment, where the removal of a designed photocatalyst did not abolish the reaction as predicted but instead led to equal or better yields. Rather than discarding this anomaly, the researchers pursued its mechanism and found that the reaction was driven by an electron donor–acceptor interaction induced simply by light. This highlights the essential role of curiosity and critical thinking in scientific research, where unexpected results can lead to transformative insights.

Machine learning has also been seamlessly integrated into the discovery workflow. Collaboration with computational scientists from Trinity College Dublin enabled the team to develop predictive models that forecast where on the molecule this reaction would occur. By training algorithms on experimental data, the researchers can simulate outcomes in silico, substantially reducing the need for costly and time-consuming laboratory trials. This synergy of artificial intelligence with experimental chemistry paves the way for smarter, more efficient drug development pipelines.

Demonstrations of the reaction across diverse drug-like molecules have showcased remarkable versatility, while adaptation to continuous-flow systems suggests strong scalability and industrial applicability. Collaboration with pharmaceutical giant AstraZeneca confirmed that this approach meets both practical and environmental standards required for large-scale pharmaceutical production. The transition from batch chemistry to continuous operation is an important step toward meeting the demands of real-world manufacturing and regulatory environments.

Chemical bond formation is foundational to synthetic chemistry, underpinning everything from fuel production to the creation of complex biomolecules and medicines. The ability to selectively forge new carbon–carbon links under mild, green conditions could revolutionize late-stage drug discovery. This method’s high functional-group tolerance enables medicinal chemists to explore nuanced molecular landscapes previously too challenging or resource-intensive to access, accelerating the creation of optimized therapeutic candidates with improved efficacy and safety profiles.

This work exemplifies a growing movement across the chemical sciences to reduce reliance on hazardous metals and extreme conditions. Such progress is vital for the sustainability of not only pharmaceuticals but the entire chemical industry. By developing reactions that function efficiently under ambient conditions and minimize toxic waste, chemists can reduce energy consumption and environmental harm—a priority underscored by the ongoing global energy and climate challenges.

According to Vahey, the implications extend far beyond academic curiosity or even incremental pharmaceutical advances. The methodology introduces a powerful, yet practical, tool into the medicinal chemist’s arsenal, enabling faster exploration of chemical space and more precise manipulation of molecular architecture. He notes that while their laboratory workflow features many ordinary days, moments of discovery like this one profoundly impact future research trajectories and the industry as a whole.

Professor Reisner eloquently sums up the ethos behind their success: “As a chemist, you only need one or two good days a year—and those can come from a failed experiment.” This insight speaks to the deep scientific value of remaining open to the unexpected, embracing data anomalies, and integrating human insight with computational power to push the boundaries of what chemistry can achieve.

The study represents a landmark in photochemical synthesis and drug discovery, combining innovative photoinitiation with machine learning and green chemistry principles. If widely adopted, it could accelerate the development of safer, more effective medicines while dramatically reducing the environmental impact of pharmaceutical research and manufacturing. This breakthrough offers a compelling vision of how chemical science can evolve to meet both technological and sustainability challenges in the 21st century.

Article Title:
Anti-Friedel–Crafts alkylation via electron donor–acceptor photoinitiation

News Publication Date:
12 March 2026

Web References:
https://www.nature.com/articles/s44160-026-00994-w
http://dx.doi.org/10.1038/s44160-026-00994-w

References:
David Vahey et al, Anti-Friedel–Crafts alkylation via electron donor–acceptor photoinitiation, Nature Synthesis, DOI: 10.1038/s44160-026-00994-w

Image Credits:
Credit: Nordin Ćatić / St John’s College, Cambridge

Keywords:
Chemistry, Photochemistry, Medicinal Chemistry, Carbon–Carbon Bond Formation, Green Chemistry, Sustainable Pharmaceutical Development, Electron Donor–Acceptor Complex, Light-Driven Catalysis, Machine Learning in Chemistry, Late-Stage Functionalization