Explore the vast range of titles available.

Fibre-reinforced epoxy composites are well established in regard to load-bearing applications in the aerospace, automotive and wind power industries, owing to their light weight and high durability. These composites are based on thermoset resins embedding glass or carbon fibres 1 . In lieu of viable recycling strategies, end-of-use composite-based structures such as wind turbine blades are commonly landfilled 1 – 4 . Because of the negative environmental impact of plastic waste 5 , 6 , the need for circular economies of plastics has become more pressing 7 , 8 . However, recycling thermoset plastics is no trivial matter 1 – 4 . Here we report a transition-metal-catalysed protocol for recovery of the polymer building block bisphenol A and intact fibres from epoxy composites. A Ru-catalysed, dehydrogenation/bond, cleavage/reduction cascade disconnects the C(alkyl)–O bonds of the most common linkages of the polymer. We showcase the application of this methodology to relevant unmodified amine-cured epoxy resins as well as commercial composites, including the shell of a wind turbine blade. Our results demonstrate that chemical recycling approaches for thermoset epoxy resins and composites are achievable. The authors report a transition-metal-catalysed protocol for recovery of polymer building block bisphenol  A and intact fibres from epoxy composites, demonstrating that chemical recycling approaches for thermoset epoxy resins and composites are achievable.

Incorporation of fluoroalkyl motifs in pharmaceuticals can enhance the therapeutic profiles of the parent molecules. The hydrofluoroalkylation of alkenes has emerged as a promising route to diverse fluoroalkylated compounds; however, current methods require superstoichiometric oxidants, expensive/oxidative fluoroalkylating reagents and precious metals, and often exhibit limited scope, making a universal protocol that addresses these limitations highly desirable. Here we report the hydrofluoroalkylation of alkenes with cheap, abundant and available fluoroalkyl carboxylic acids as the sole reagents. Hydrotrifluoro-, difluoro-, monofluoro- and perfluoroalkylation are all demonstrated, with broad scope, mild conditions (redox neutral) and potential for late-stage modification of bioactive molecules. Critical to success is overcoming the exceedingly high redox potential of feedstock fluoroalkyl carboxylic acids such as trifluoroacetic acid by leveraging cooperative earth-abundant, inexpensive iron and redox-active thiol catalysis, enabling these reagents to be directly used as hydroperfluoroalkylation donors without pre-activation. Preliminary mechanistic studies support the radical nature of this cooperative process.Alkene hydrofluoroalkylation offers a promising route to diverse fluoroalkylated compounds but current methods have limitations, such as needing expensive fluoroalkylating reagents. Now, leveraging iron photocatalysis and hydrogen-atom-transfer catalysis, a hydrofluoroalkylation method has been developed that utilizes feedstock chemicals such as trifluoroacetic acid as direct fluoroalkyl radical precursors, providing a redox-neutral, general protocol to introduce fluoroalkyl moieties.

Cross-coupling reactions are among the most important transformations in modern organic synthesis 1 – 3 . Although the range of reported (het)aryl halides and nucleophile coupling partners is very large considering various protocols, the reaction conditions vary considerably between compound classes, necessitating renewed case-by-case optimization of the reaction conditions 4 . Here we introduce adaptive dynamic homogeneous catalysis (AD-HoC) with nickel under visible-light-driven redox reaction conditions for general C( sp 2 )–(hetero)atom coupling reactions. The self-adjustive nature of the catalytic system allowed the simple classification of dozens of various classes of nucleophiles in cross-coupling reactions. This is synthetically demonstrated in nine different bond-forming reactions (in this case, C( sp 2 )–S, Se, N, P, B, O, C( sp 3 ,  sp 2 ,  sp ), Si, Cl) with hundreds of synthetic examples under predictable reaction conditions. The catalytic reaction centre(s) and conditions differ from one another by the added nucleophile, or if required, a commercially available inexpensive amine base. A self-adjustive catalytic system with nickel under visible-light-driven redox reaction conditions provides a general method for carbon–(hetero)atom cross-coupling reactions and is demonstrated for nine different bond-forming reactions.

A major roadblock in realizing large-scale production of hydrogen via electrochemical water splitting is the cost and inefficiency of current catalysts for the oxygen evolution reaction (OER). Computational research has driven important developments in understanding and designing heterogeneous OER catalysts using linear scaling relationships derived from computed binding energies. Herein, we interrogate 17 of the most active molecular OER catalysts, based on different transition metals (Ru, Mn, Fe, Co, Ni, and Cu), and show they obey similar scaling relations to those established for heterogeneous systems. However, we find that the conventional OER descriptor underestimates the activity for very active OER complexes as the standard approach neglects a crucial one-electron oxidation that many molecular catalysts undergo prior to O–O bond formation. Importantly, this additional step allows certain molecular catalysts to circumvent the “overpotential wall”, leading to enhanced performance. With this knowledge, we establish fundamental principles for the design of ideal molecular OER catalysts. While water electrolysis affords hydrogen as a carbon-neutral fuel, the oxygen evolution half-reaction limits overall performances. Here, authors examine molecular catalysts and their water oxidation mechanisms via computational methods.

Glycans have diverse physiological functions, ranging from energy storage and structural integrity to cell signalling and the regulation of intracellular processes 1 . Although biomass-derived carbohydrates (such as d -glucose, d -xylose and d -galactose) are extracted on commercial scales, and serve as renewable chemical feedstocks and building blocks 2 , 3 , there are hundreds of distinct monosaccharides that typically cannot be isolated from their natural sources and must instead be prepared through multistep chemical or enzymatic syntheses 4 , 5 . These ‘rare’ sugars feature prominently in bioactive natural products and pharmaceuticals, including antiviral, antibacterial, anticancer and cardiac drugs 6 , 7 . Here we report the preparation of rare sugar isomers directly from biomass carbohydrates through site-selective epimerization reactions. Mechanistic studies establish that these reactions proceed under kinetic control, through sequential steps of hydrogen-atom abstraction and hydrogen-atom donation mediated by two distinct catalysts. This synthetic strategy provides concise and potentially extensive access to this valuable class of natural compounds. Various rare sugars that cannot be isolated from natural sources are synthesized using light-driven epimerization, a process which may find application in other synthetic scenarios.

Hydrogen atom abstraction (HAT) from C( sp 3 )–H bonds of naturally abundant alkanes for alkyl radical generation represents a promising yet underexplored strategy in the alkylation reaction designs since involving stoichiometric oxidants, excessive alkane loading, and limited scope are common drawbacks. Here we report a photo-induced and chemical oxidant-free cross-dehydrogenative coupling (CDC) between alkanes and heteroarenes using catalytic chloride and cobalt catalyst. Couplings of strong C( sp 3 )–H bond-containing substrates and complex heteroarenes, have been achieved with satisfactory yields. This dual catalytic platform features the in situ engendered chlorine radical for alkyl radical generation and exploits the cobaloxime catalyst to enable the hydrogen evolution for catalytic turnover. The practical value of this protocol was demonstrated by the gram-scale synthesis of alkylated heteroarene with merely 3 equiv. alkane loading. Hydrogen atom abstraction from C( sp 3 )–H bonds of naturally abundant alkanes for alkyl radical generation represents a promising yet underexplored strategy in the alkylation reaction designs. Here the authors show a photo-induced and chemical oxidant-free cross-dehydrogenative coupling between alkanes and heteroarenes using catalytic chloride and cobalt catalyst.

The intermolecular three-component alkene vicinal dicarbofunctionalization (DCF) reaction allows installation of two different carbon fragments. Despite extensive investigation into its ionic chemistry, the enantioseletive radical-mediated versions of DCF reactions remain largely unexplored. Herein, we report an intermolecular, enantioselective three-component radical vicinal dicarbofunctionalization reaction of olefins enabled by merger of radical addition and cross-coupling using photoredox and copper dual catalysis. Key to the success of this protocol relies on chemoselective addition of acyl and cyanoalkyl radicals, generated in situ from the redox-active oxime esters by a photocatalytic N-centered iminyl radical-triggered C-C bond cleavage event, onto the alkenes to form new carbon radicals. Single electron metalation of such newly formed carbon radicals to TMSCN-derived L1 Cu(II)(CN) 2 complex leads to asymmetric cross-coupling. This three-component process proceeds under mild conditions, and tolerates a diverse range of functionalities and synthetic handles, leading to valuable optically active β –cyano ketones and alkyldinitriles, respectively, in a highly enantioselective manner (>60 examples, up to 97% ee). Vicinal dicarbofunctionalization (DCF) reactions of alkenes have been extensively explored in ionic chemistry but the enantioselective radical mediated version of DCF remains largely unexplored. Here, the authors demonstrate a radical vicinal DCF reaction of olefins by merging of radical addition and cross-coupling using photoredox and copper dual catalysis.

Catalytic hydrogenation of amides is of great interest for chemists working in organic synthesis, as the resulting amines are widely featured in natural products, drugs, agrochemicals, dyes, etc. Compared to traditional reduction of amides using (over)stoichiometric reductants, the direct hydrogenation of amides using molecular hydrogen represents a greener approach. Furthermore, amide hydrogenation is a highly versatile transformation, since not only higher amines (obtained by C–O cleavage), but also lower amines and alcohols, or amino alcohols (obtained by C–N cleavage) can be selectively accessed by fine tuning of reaction conditions. This review describes the most recent advances in the area of amide hydrogenation using H 2 exclusively and molecularly defined homogeneous as well as nano-structured heterogeneous catalysts, with a special focus on catalyst development and synthetic applications. Catalytic hydrogenation of amides is a pivotal chemical transformation for both research labs and chemical production in industry. Here, the authors comprehensively review this topic by including state-of-art homogeneous and heterogeneous catalysts that can hydrogenate amides and related compounds.

Plastics pollution is causing an environmental crisis, prompting the development of new approaches for recycling, and upcycling. Here, we review challenges and opportunities in chemical and biological catalysis for plastics deconstruction, recycling, and upcycling. We stress the need for rigorous characterization and use of widely available substrates, such that catalyst performance can be compared across studies. Where appropriate, we draw parallels between catalysis on biomass and plastics, as both substrates are low-value, solid, recalcitrant polymers. Innovations in catalyst design and reaction engineering are needed to overcome kinetic and thermodynamic limitations of plastics deconstruction. Either chemical and biological catalysts will need to act interfacially, where catalysts function at a solid surface, or polymers will need to be solubilized or processed to smaller intermediates to facilitate improved catalyst–substrate interaction. Overall, developing catalyst-driven technologies for plastics deconstruction and upcycling is critical to incentivize improved plastics reclamation and reduce the severe global burden of plastic waste. Plastics are invaluable materials for modern society, although they result in the generation of large amounts of litter at the end of their life cycle. This Review explores the challenges and opportunities associated with the catalytic transformation of waste plastics, looking at both chemical and biological approaches to transforming such spent materials into a resource.

Using a ligand as a promoter enhances the reactivity of the palladium catalyst in non-directed C–H functionalization of arenes, enabling the arene to be used as the limiting reagent. The catalyst does it all The functionalization of a carbon–hydrogen (C–H) bond is one of the most useful reactions in organic synthesis as it precludes the need to install reactive groups to perform a reaction. However, the reactivity and number of C–H bonds that are present in organic molecules mean that selectively targeting one is challenging. Typically this has been achieved by 'directing groups', where proximity to a specific C–H bond guides the reaction. Now, Jin-Quan Yu and colleagues report a palladium-catalysed non-directed arene C–H functionalization method using a 2-pyridone ligand. The ligand makes the catalyst more reactive, allowing the arene to be used as the limiting reagent—overcoming a key limitation in the use of such reactions in the derivatization of complex molecules. The ligand also enhances the effects of sterics on site selectivity, in some cases improving it significantly without the need for a directing group. The directed activation of carbon–hydrogen bonds (C–H) is important in the development of synthetically useful reactions, owing to the proximity-induced reactivity and selectivity that is enabled by coordinating functional groups 1 , 2 , 3 , 4 , 5 , 6 . Palladium-catalysed non-directed C–H activation could potentially enable further useful reactions, because it can reach more distant sites and be applied to substrates that do not contain appropriate directing groups; however, its development has faced substantial challenges associated with the lack of sufficiently active palladium catalysts 7 , 8 . Currently used palladium catalysts are reactive only with electron-rich arenes, unless an excess of arene is used 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , which limits synthetic applications. Here we report a 2-pyridone ligand that binds to palladium and accelerates non-directed C–H functionalization with arene as the limiting reagent. This protocol is compatible with a broad range of aromatic substrates and we demonstrate direct functionalization of advanced synthetic intermediates, drug molecules and natural products that cannot be used in excessive quantities. We also developed C–H olefination and carboxylation protocols, demonstrating the applicability of our methodology to other transformations. The site selectivity in these transformations is governed by a combination of steric and electronic effects, with the pyridone ligand enhancing the influence of sterics on the selectivity, thus providing complementary selectivity to directed C–H functionalization.