The carbonyl–ene reaction belongs to a family of transformations in which an alkene and a carbonyl compound reorganize their atoms to create a new carbon–carbon bond. In a typical ene-type process, an alkene bearing a transferable allylic hydrogen interacts with a carbonyl group. The hydrogen migrates to the carbonyl oxygen, the double bond changes position, and a new bond forms between the alkene and carbonyl carbon. The product is generally an alcohol with a newly modified carbon skeleton. Although the overall rearrangement is conceptually simple, it requires precise control over orbital alignment, energy and competing reaction pathways. In intermolecular versions, the two reacting molecules must also find one another in solution in the correct orientation.

The difficulty becomes greater when the alkene is “unactivated.” Activated alkenes contain nearby electron-withdrawing or otherwise directing groups that make them more reactive toward a carbonyl partner. Unactivated alkenes lack those advantages. They are chemically less eager to participate, and they can undergo several alternative reactions, including alkene isomerization, polymerization or simple decomposition under forcing conditions. Aldehydes present their own complications: they are reactive enough to engage in unwanted side reactions, yet the desired carbonyl–ene pathway may remain too slow without carefully designed catalysis. Bringing these two uncooperative partners together selectively has therefore been a longstanding target in catalytic chemistry.

The new work is significant because it combines three demanding objectives in a single intermolecular transformation. First, it uses aldehydes and alkenes that are not pre-engineered with highly reactive functional groups. Second, it forms a carbon–carbon bond between separate molecules rather than rearranging a substrate that already contains both reaction partners. Third, it introduces asymmetry, meaning that the catalyst guides the reaction toward one three-dimensional arrangement of the product over its mirror-image alternative. Enantiomeric control is crucial in medicinal chemistry because two mirror-image molecules can interact very differently with biological targets, even when they have the same atoms and connectivity.

At the heart of an asymmetric reaction is a chiral catalytic environment. A catalyst accelerates the transformation without being consumed, while its three-dimensional architecture can make one approach of the alkene to the aldehyde more favorable than the other. In a successful carbonyl–ene-type process, this control must operate while the catalyst also activates the carbonyl, organizes the two substrates and suppresses competing pathways. The product’s stereochemistry is established as the new carbon–carbon bond and alcohol-bearing center are formed. Achieving these tasks with unactivated components is especially demanding because weak differences in transition-state energy can determine whether a reaction is fast, selective and useful—or produces a mixture that is difficult to separate.

The researchers’ strategy illustrates a broader trend in modern synthesis: replacing preactivation with catalytic organization. Traditional approaches often convert starting materials into more reactive derivatives before coupling them, generating additional steps and chemical waste. A catalytic reaction that works directly with aldehydes and simple alkenes could shorten synthetic sequences and make molecular assembly more efficient. The carbonyl and alkene partners are among the most familiar functional groups in organic chemistry, and their abundance means that the method may offer a flexible platform for constructing more elaborate compounds. Its value will ultimately depend on how many substrate classes tolerate the conditions, how efficiently the products can be isolated and how readily the catalyst can be used at larger scale.

The reaction also offers a lesson in selectivity. Chemists generally evaluate a transformation not only by whether it occurs, but by where it occurs and what stereochemical form it produces. Aldehydes can react at multiple sites, while alkenes may possess more than one possible orientation or can rearrange before bond formation. A useful catalytic system must distinguish among these possibilities. In an asymmetric intermolecular setting, the catalyst is effectively solving a molecular recognition problem: it must bring together two freely moving molecules, select the productive alignment and then lock in the desired three-dimensional outcome. That combination of reactivity and discrimination is what makes the reported chemistry more than a simple addition reaction.

For drug discovery, reactions of this kind could be particularly valuable because alcohols and adjacent stereocenters appear throughout biologically active molecules. A direct method for installing such features may enable medicinal chemists to prepare analogues rapidly, changing the size, shape and spatial orientation of candidate compounds without rebuilding them from scratch. In natural-product synthesis, the same reaction logic could help connect fragments while establishing stereochemistry in a single operation. Beyond pharmaceuticals, asymmetric carbon–carbon-bond-forming reactions are relevant to agrochemicals, fragrances and advanced materials, where the precise arrangement of atoms can influence stability, biological activity or physical properties.

The findings do not eliminate every challenge associated with carbonyl–ene chemistry. As with any emerging catalytic method, future studies will need to define its full substrate scope, clarify the detailed catalytic mechanism and test its performance with increasingly complex molecules. Researchers will also be interested in catalyst loading, reaction speed, scalability and the recovery or recycling of the catalyst. Mechanistic information could reveal whether the key step proceeds through direct activation of the aldehyde, a catalyst-bound intermediate or another coordinated pathway. Such knowledge may allow the method to be extended to less reactive alkenes, more sensitive aldehydes or other classes of carbonyl compounds.

Nevertheless, the study marks a striking advance in the effort to make simple molecules behave with the precision normally associated with highly engineered substrates. By enabling an asymmetric intermolecular carbonyl–ene-type reaction between unactivated aldehydes and alkenes, the researchers have opened a route to chiral structures through a bond-forming event that is both conceptually economical and synthetically powerful. The broader message is clear: sophisticated catalyst design can turn weakly reactive, commonplace molecules into partners capable of building complexity directly. In a field increasingly focused on efficiency, selectivity and sustainable synthesis, that kind of molecular shortcut is exactly the sort of chemistry that can spread rapidly from the research laboratory into the toolkits of scientists designing the next generation of medicines and materials.

Subject of Research: Catalytic asymmetric intermolecular carbonyl–ene-type reactions of unactivated aldehydes and alkenes

Article Title: Catalytic asymmetric intermolecular carbonyl–ene-type reactions of unactivated aldehydes and alkenes

Article References: Grimm, J.A.A., Shi, L., Tsuji, N. et al. Catalytic asymmetric intermolecular carbonyl–ene-type reactions of unactivated aldehydes and alkenes. Nature Catalysis 9, 893–900 (2026). https://doi.org/10.1038/s41929-026-01589-6

Image Credits: AI Generated

DOI: 10.1038/s41929-026-01589-6

Keywords: asymmetric catalysis, carbonyl–ene reaction, aldehydes, unactivated alkenes, intermolecular reactions, carbon–carbon bond formation, chiral molecules, organic synthesis

Internal alkenes are common in complex organic molecules, but they are considerably more difficult to functionalize than terminal alkenes. Their substituents crowd the carbon–carbon double bond, making it harder for a metal catalyst to approach and insert into the alkene. At the same time, the two alkene carbons often offer similar electronic environments, so the catalyst may generate mixtures of regioisomers rather than a single defined product. Internal alkenes can also migrate along a carbon chain through isomerization, while the alkyl–metal intermediates formed during catalysis may undergo β-hydride elimination. These competing pathways can destroy both efficiency and stereochemical control. Although directing groups have previously helped guide metal catalysts toward internal alkenes, those groups must usually be installed and later removed, adding extra steps to a synthesis.

The new strategy addresses these challenges through the combined design of the nickel catalyst, the NHC ligand and the reaction medium. The NHC ligands used by the researchers are sterically demanding but structurally flexible. Their bulky substituents help shield the reactive nickel center and suppress unwanted β-hydride elimination, while their flexible framework allows the catalyst to accommodate crowded internal alkenes during migratory insertion. The ligand also creates a chiral pocket around the metal. As the alkene enters this environment, one of its two possible orientations is favored over the other, allowing the reaction to generate predominantly one enantiomer of the product. This control is essential because enantiomers can have dramatically different biological properties, even though they share the same molecular formula and connectivity.

The team first optimized the reaction using 2,5-dihydrofuran, a cyclic internal alkene, and an aryl trifluoromethanesulfonate. Screening a series of NHC ligands revealed that structures bearing bulky 3,5-dimethylphenyl groups were particularly effective. The optimized system delivered β-arylated chiral dihydrofuran products in high yield and with strong enantiomeric enrichment. Solvent selection proved to be unusually important. Isopropanol, or iPrOH, improved not only the chemical yield but also chemoselectivity and enantioselectivity. The result is notable because asymmetric Heck chemistry involving 2,5-dihydrofuran has been difficult to achieve, in part because this substrate can isomerize and because the catalyst must control both the position and the three-dimensional outcome of aryl addition.

The reductive Heck coupling displayed a broad electrophile scope. Aryl trifluoromethanesulfonates containing electron-donating or electron-withdrawing substituents underwent the transformation efficiently. The compatible groups included aniline, ether, fluorine, ester and acetal functionalities, as well as drug-related heterocycles such as morpholine, benzofuran and dibenzofuran. The resulting products were generally obtained with high yields and enantiomeric excesses ranging from 88% to 94%. Alkenyl trifluoromethanesulfonates could also participate, allowing the preparation of trisubstituted alkenes. This range is important for pharmaceutical chemistry, where late-stage coupling methods must tolerate many functional groups without requiring extensive protection or deprotection strategies.

The alkene component was similarly versatile. In addition to 2,5-dihydrofuran, the reaction accepted N-Boc-, N-Cbz- and N-PMP-protected dihydropyrroles, substituted styrene-derived internal alkenes and sulfur- or oxygen-containing cyclic systems. Functional groups such as ethers, fluorine, chlorine and silyl-protected alcohols remained intact during the reaction. Thiochromene-, chromene-, acyclic and bridged cyclic alkenes could also be transformed, with the best examples reaching approximately 94% enantiomeric excess. In one gram-scale experiment using 8.0 millimoles of substrate, the desired product was isolated in 95% yield and 90% enantiomeric excess. Such a result suggests that the chemistry is not limited to small exploratory reactions and may be adaptable to the preparation of useful quantities of chiral intermediates.

The researchers also examined the conventional asymmetric Heck pathway, in which the alkyl–nickel intermediate undergoes β-hydride elimination to form an alkene rather than receiving a hydrogen atom. Using lithium tert-butoxide as the base and tert-butanol as the solvent, the sterically hindered NHC ligand enabled the coupling of 2,5-dihydrofuran with an aryl trifluoromethanesulfonate to produce a β-arylated product in 92% yield and 94% enantiomeric excess. The reaction accommodated ortho-, meta- and para-substituted aryl partners, as well as compounds bearing aniline, ether, fluorine, chlorine, ester, acetal and methylthio groups. Heterocyclic and alkenyl electrophiles also reacted successfully, providing a direct route to β-arylated chiral dihydrofurans.

Mechanistic experiments indicate that the reaction does not follow the most familiar nickel-hydride pathway. Deuterium-labeling studies showed that the hydrogen incorporated into reductive Heck products originates from the methine group of isopropanol or from isopropoxide, rather than from a preformed nickel–hydrogen species. Control experiments established that the aryl trifluoromethanesulfonate is necessary to initiate catalysis, while radical-trapping tests did not suppress the reaction, arguing against a free-radical mechanism. Kinetic measurements found the process to be zero-order in both the alkene and the aryl electrophile but first-order in catalyst concentration, suggesting that catalyst activation or a catalyst-centered step influences the overall rate.

On the basis of these observations, the authors propose a catalytic cycle beginning with oxidative addition of the aryl trifluoromethanesulfonate to a Ni(0)–NHC complex, generating an aryl–nickel(II) intermediate. The internal alkene then inserts into the nickel–carbon bond in a regioselective and enantioselective fashion, forming a chiral alkyl–nickel species. If isopropoxide is absent, β-hydride elimination dominates and produces the Heck-coupled alkene. When isopropoxide is present, hydrogen transfer and reductive elimination instead release the reduced arylated product and regenerate the active catalyst. The bulky, flexible NHC ligand is central to this balance: it discourages unproductive β-hydride elimination when reduction is desired, promotes insertion of sterically hindered alkenes and maintains a chiral environment throughout the bond-forming steps.

By combining broad functional-group tolerance with control over both regioselectivity and enantioselectivity, the nickel/NHC system offers a potentially general platform for modifying internal alkenes without directing groups. The products include chiral dihydrofurans, dihydropyrroles, chromene-related structures and thiochromene-related structures, many of which resemble frameworks found in biologically active compounds. The study also demonstrates how ligand architecture can solve several problems at once: steric protection of the metal center, selective alkene insertion, suppression of side reactions and asymmetric induction. Published as an open-access research article in CCS Chemistry, the work could attract attention well beyond catalytic methodology because it provides a practical way to add complexity to molecules late in a synthesis—one of the most sought-after capabilities in modern drug discovery and chemical manufacturing.

Subject of Research: Asymmetric functionalization of internal cyclic alkenes using nickel/N-heterocyclic carbene catalysis.

Article Title: Enantioselective Reductive Heck and Heck Coupling of Internal Cyclic Alkenes Enabled by Nickel/N-Heterocyclic Carbene Catalysis

News Publication Date: 10-Jul-2026

Web References: CCS Chemistry, https://doi.org/10.31635/ccschem.026.202607864

References: Wu, Hai-Yu, et al. “Enantioselective Reductive Heck and Heck Coupling of Internal Cyclic Alkenes Enabled by Nickel/N-Heterocyclic Carbene Catalysis.” CCS Chemistry. DOI: 10.31635/ccschem.026.202607864

Image Credits: CCS Chemistry

Keywords

Nickel catalysis, N-heterocyclic carbene, asymmetric synthesis, reductive Heck reaction, Heck coupling, internal alkenes, enantioselective catalysis, chiral molecules, organic chemistry, drug discovery

At the heart of this innovation lies the asymmetric bimetallic synergistic copper-catalyzed propargyl substitution (CuAPS), an elegant transformation where the activation of both the propargyl electrophile and α-cyano ester nucleophile is finely orchestrated. This is mediated by a chiral Cu(I)–BOX complex catalyst, which not only recognizes the subtle electronic landscapes of both substrates but also transiently assembles into a binuclear complex of quasi-C₂ symmetry. This dynamic entity, combining a Cu-propynyl intermediate on one side and a stabilized deprotonated α-cyano ester on the other, facilitates an exquisitely stereoselective carbon–carbon bond formation. The conformational locking enabled by H···π stacking interactions underpins the high enantio- and diastereoselectivity achieved, culminating in yields of cyclic imidates with enantioselectivities as high as 94%.

This breakthrough addresses a longstanding challenge in asymmetric synthesis: the comprehensive activation and stereocontrol over both partners in propargyl substitution reactions. Historically, the understanding of catalytic activation modes has been fragmented, limiting the scope and efficiency of constructing chiral propargyl skeletons. Moreover, chiral cyclic imides—particularly those accessed as N-unprotected variants—have remained elusive targets due to synthetic limitations. The approach presented here revolutionizes this field by harnessing a transiently formed, dual-copper catalytic system that effectively lowers activation barriers and unlocks previously inaccessible chemical space.

One of the most striking facets of this method is its broad substrate scope and robustness under mild reaction conditions. The system tolerates diverse propargyl carbonates and α-cyano esters bearing a variety of functional groups, enabling the rapid assembly of structurally diverse chiral cyclic imidates. This versatility not only expands the utility of chiral imidates but also opens myriad avenues for late-stage functionalization and derivatization, positioning these scaffolds as versatile building blocks in synthetic and medicinal chemistry.

The potential of the synthesized cyclic imine esters extends well beyond their immediate formation. Their rich functional group profile, including reactive N–H and alkynyl groups, permits facile post-synthetic modification. Using strategies such as N-alkylation and the Sonogashira cross-coupling reaction, researchers can swiftly access a library of chiral imidate derivatives with tailored properties. This modularity is particularly valuable in drug discovery, where rapid generation of analogues is critical for structure-activity relationship studies and optimization of pharmacological profiles.

In a compelling demonstration of the biomedical promise embedded in these new compounds, several derivatives exhibited remarkable antiviral activity against the feline calicivirus (FCV) infection model. The antiviral efficacy surpassed that of nitrozonide, a benchmark positive control drug, highlighting these chiral imidates not only as chemical curiosities but also as potential therapeutic leads. This intersection of synthetic innovation and biological relevance underscores the translational impact of the research and fuels optimism for future drug development endeavors centered on these novel scaffolds.

The mechanistic insights gained through this work are equally transformative. The transient binuclear copper complex and its quasi-C₂ symmetric nature elucidate how the cooperative interplay between two distinct copper catalytic centers can be tactically exploited to direct stereochemical outcomes with precision. Such mechanistic clarity paves the way for the rational design of next-generation bimetallic catalysts tailored for other challenging asymmetric transformations, signaling a paradigm shift in catalyst development.

From a practical perspective, the catalytic efficiency demonstrated—manifested in high substrate-to-catalyst ratios (S/C up to 2000)—and mild reaction milieu suggest scalability and potential industrial applicability. The synthetic accessibility and operational simplicity may transform how chiral cyclic imidates are produced at scale, benefiting sectors ranging from pharmaceutical synthesis to agrochemicals and materials science.

This research also embodies the spirit of international collaboration and support, having been facilitated by foundational grants provided by the Fundamental Research Funds for the Central Universities and Shanghai Jiao Tong University’s Research Start-up Fund. The choice to publish open access in CCS Chemistry, a premier platform established by the Chinese Chemical Society to disseminate cutting-edge chemical research globally, ensures that these scientific advancements are readily accessible to the worldwide community, accelerating innovation.

The Chinese Chemical Society, established in 1932 and now comprising over 120,000 members worldwide, continues to foster the growth and development of chemistry in China and beyond. Its flagship publication CCS Chemistry serves as a beacon for seminal discoveries like this, bridging frontiers in fundamental chemistry and its applications with open sharing of knowledge.

Ultimately, this study represents a hallmark achievement in asymmetric catalysis, with the dual copper-catalyzed tandem reaction epitomizing synergy at the molecular level to unlock new chemical transformations. The confluence of mechanistic insight, synthetic scope, catalytic performance, and biological activity exemplifies the multidisciplinary impact of modern chemistry, affirming its pivotal role in addressing both scientific and societal challenges.

As researchers delve deeper into the subtleties of bimetallic synergy and continue optimizing related catalytic systems, the horizon promises even more unprecedented reactions, new classes of chiral molecules, and potential breakthroughs in drug discovery. The chiral N-unprotected cyclic imidates synthesized through this elegant methodology are poised to become indispensable tools, laying the foundation for future innovations in chemical synthesis and therapeutic development.

Subject of Research: Not applicable

Article Title: Bimetallic Copper-Catalyzed Asymmetric Propargylic Substitution: Synthesis of Chiral N-Unprotected Imidates, Mechanistic Study, and Antiviral Activity

News Publication Date: 5-Mar-2026

Web References:
– CCS Chemistry Journal: https://www.chinesechemsoc.org/journal/ccschem
– Chinese Chemical Society: https://www.chinesechemsoc.org/

References:
DOI: 10.31635/ccschem.026.202507061

Image Credits: CCS Chemistry

Keywords

Catalysis, Asymmetric synthesis, Copper catalysis, Propargyl substitution, Chiral imidates, Binuclear catalysis, Tandem reaction, Enantioselectivity, Pinner reaction, Antiviral compounds, Medicinal chemistry, Chiral ligand design

Recent advances have spotlighted enantiomerically enriched boronic esters as versatile intermediates that allow for the rapid assembly of diverse molecular frameworks. Their stereochemical integrity and broad applicability endow them with immense potential in the modular synthesis of bioactive compounds, pharmaceuticals, and natural product analogs. Yet, the catalytic transformation of these species, particularly in the context of stereospecific alkyl-alkyl couplings, has remained an elusive challenge. The stereogenic nature of the sp^3-hybridized carbons involved often leads to issues of selectivity, reaction efficiency, and functional group compatibility.

Addressing this gap, a groundbreaking study led by researchers Zhang, Palka, Zhang, and colleagues has unveiled a novel copper-catalyzed stereospecific C(sp^3)–C(sp^3) cross-coupling reaction employing four-coordinate boron “ate” complexes. This transformative approach not only demonstrates high stereochemical fidelity but also showcases an unprecedented tolerance towards various functional groups, including unreacted boronic esters within the substrate milieu. Such unique chemoselectivity represents a significant leap forward in broadening the synthetic utility of organoboron compounds.

At the heart of this innovation lies the strategic exploitation of copper acetylide complexes as catalysts, which deftly navigate the challenges traditionally associated with alkyl-alkyl couplings. Unlike palladium or nickel-based systems, copper catalysis introduces distinct mechanistic pathways that afford better control over stereochemical outcomes. The researchers meticulously optimized reaction parameters to ensure that the copper catalyst engages selectively with the boron “ate” intermediates, facilitating stereospecific carbon-carbon bond formation without compromising sensitive functional groups present in complex molecules.

This method’s ability to retain stereochemical integrity through the coupling sequence is particularly remarkable, given the propensity for alkyl centers adjacent to stereogenic carbons to undergo racemization or competing side reactions. By employing a strategy that leverages the configurational stability of the four-coordinate boron “ate” complexes, the team successfully preserved enantiomeric purity during the cross-coupling events. This achievement opens pathways to synthesizing chiral molecules with defined three-dimensional orientation, a crucial factor influencing biological activity and drug-like properties.

Functionally, the methodology exhibits a broad substrate scope, accommodating a variety of alkyl boronic esters and diverse electrophiles. Its robustness and operational simplicity underscore its practical value for synthetic chemists aiming to assemble complex molecular frameworks rapidly and efficiently. The reaction conditions display admirable tolerance for commonly encountered functional groups such as ethers, esters, and unprotected alcohols, diminishing the need for extensive protective group strategies that often complicate synthetic routes.

The implications of this copper-catalyzed stereospecific cross-coupling extend beyond academic curiosity. The research team demonstrated the synthetic potential of their methodology through the total synthesis of (–)-spongidepsin, a marine natural product renowned for its biological activities, and through the construction of the intricate carbon skeleton of fluvirucinine A1, a molecule of pharmaceutical relevance. These applications underscore how this approach can streamline synthetic efforts toward complex bioactive targets, facilitating access to molecules that would otherwise be challenging to synthesize with precise stereochemical control.

Mechanistically, the coupling entails initial formation of a copper acetylide species, which then engages the four-coordinate boron “ate” complex in a stereospecific transmetalation step. This pivotal step transfers the alkyl group with retention of stereochemistry, contrasting with many prior methodologies where configuration was often lost or obscured. The subsequent reductive elimination step closes the catalytic cycle, delivering the desired alkyl-alkyl coupled product while regenerating the copper catalyst. The careful orchestration of these mechanistic stages is central to achieving the stereochemical and functional group compatibility observed.

Notably, the strategy’s insensitivity to other boronic esters present during the reaction provides a unique handle for sequential and iterative coupling reactions. Chemists can therefore envision multi-step transformations where boronic esters serve as latent coupling partners, activated selectively in the presence of other potentially reactive sites. This modularity promises to revolutionize synthetic planning and accelerate the discovery of novel molecular entities across medicinal chemistry and material science domains.

This advancement is emblematic of the broader movement within organic chemistry to harness earth-abundant metals like copper in catalytic transformations traditionally dominated by precious metals. By developing cost-effective and sustainable methodologies that do not compromise on efficiency or selectivity, researchers contribute significantly to greener and more scalable chemical synthesis. The accessible nature of copper catalysts also widens the potential for industrial adoption, thereby amplifying the impact of such discoveries.

As synthetic challenges become increasingly complex, innovations like this stereospecific copper-mediated alkyl-alkyl coupling offer elegant solutions to assemble carbon skeletons with intricacy and precision. The interplay of mechanistic insight, catalyst design, and substrate engineering exemplifies the creative ingenuity at the core of modern chemical research. The publication of these findings in a leading journal such as Nature further emphasizes the significance of the work and its prospective influence on multiple fields.

In summary, the novel copper acetylide-catalyzed cross-coupling of four-coordinate boron “ate” complexes represents a milestone in stereospecific C(sp^3)–C(sp^3) bond formation. It addresses longstanding challenges in boronic ester chemistry, expands the toolkit available to synthetic chemists, and unlocks new avenues for the synthesis of complex, chiral molecules. As this methodology gains traction, it is poised to transform strategies in natural product synthesis, drug development, and the broader scope of modular organic synthesis for years to come.

Subject of Research: Development of a stereospecific C(sp^3)–C(sp^3) cross-coupling reaction of enantiomerically enriched boronic esters catalyzed by copper acetylide complexes.

Article Title: Stereospecific alkyl–alkyl cross-coupling of boronic esters.

Article References:

Zhang, X., Palka, K.T., Zhang, M. et al. Stereospecific alkyl–alkyl cross-coupling of boronic esters.
Nature (2026). https://doi.org/10.1038/s41586-026-10261-9

Image Credits: AI Generated