ACS Chemical Biology最新文献

The direct catalytic reductive functionalization of nitroarenes to produce amines with enhanced properties continues to attract attention for both academic and industrial synthesis. However, most previous reports on the reductive functionalization of nitroarenes were based on C-NAr bond formation; the reductive functionalization on the aryl group for the synthesis of functionalized anilines has been scarcely reported. Here, we report a reductive ortho-allylation of nitroarenes with 1,3-dienes via molybdenum catalysis. Various ortho-allyl anilines were regioselectively produced in favorable yields from easily accessible precursor materials. This work represents a unique instance of the reductive functionalization of nitroarenes which forms a C–C bond on the aryl group to synthesize functionalized anilines. Notable features of this work include: (1) the reductive functionalization of nitroarenes on the aryl group, (2) high stereoconvergent synthesis, wherein the mixtures of E/Z isomers of 1,3-dienes selectively yield E-isomer products, and (3) broad substrate scopes, accompanied by favorable yields and selectivity.

We introduce a phosphine-catalyzed cycloaddition involving unprecedented long-range intramolecular proton transfer, facilitating the synthesis of nine-membered heterocycles, which are privileged structures in natural products, as well as potent pharmacophores. Experimental and computational studies revealed that the enamide tether of the N-aromatic zwitterion directly enables long-range regioselective intramolecular proton transfer to proceed independently of outer-sphere proton shuttling. This understanding of selective proton transfer has led to the improved efficiency and regioselectivity of the desired 1,9-proton transfer reaction under anhydrous conditions, thereby advancing the development of higher-order cycloaddition reactions. Further stereoselective contraction of the synthesized nine-membered cyclic compounds using 3-aza-Cope rearrangement demonstrates the synthetic versatility of our approach. The findings of this study not only advance the general understanding of the long-range proton transfer mechanism but also broaden its practical utility in various chemical fields.

The electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) provides a viable pathway for the efficient utilization of biomass resources. However, designing and regulating the activity and selectivity of the corresponding electrocatalysts remain significant challenge. Spinel compounds show great potential as catalysts due to their adjustable electronic structures and notable catalytic properties, but their intrinsic low conductivity has limited their further application. Herein, a lignin-based carbon fiber (LCF) embedded CuFe₂O₄ catalyst (CuFe₂O₄/LCF) is successfully constructed using an electrospinning technique. The catalyst can efficiently and selectively synthesize 2,5-furandicarboxylic acid (FDCA) at a relatively low potential. The experimental results and theoretical simulations demonstrate that the introduction of lignin can significantly optimize the pregraphitic turbine carbon microstructure of the carbon fibers and facilitate rapid electron transfer between CuFe₂O₄ and the carbon layer. Furthermore, the A_Td–O–B_Oh interactions on the surface of the CuFe₂O₄ spinel structure significantly enhance the adsorption capacity for the substrates and OH^– species, effectively promoting the catalytic reaction. The findings hope to provide a unique perspective to improve the catalytic activity of lignin carbon fiber spinel catalysts and the stability of biomass value-added mechanism.

Lignin is the most abundant aromatic source of natural products, but developing efficient catalysts to depolymerize it into valuable monophenol with high yield and unique selectivity remains a challenge. Herein, we report a Ru single-atom catalyst (SAC) supported on rod CeO₂ with oxygen vacancies (Ov) for the depolymerization of birch dioxane acidolysis lignin (DAL). A near-theoretical maximum monophenol yield (14.8 wt %) with good selectivity to 4-n-propenyl guaiacol (51.4%), as well as high catalyst stability, was achieved. The calculated turnover (TON) was 387 mol_aromatics/mol_Ru, which is 55× higher than that of the Ru/C catalyst. The possible reaction for this catalyst was proposed by studying a series of lignin model compounds and in situ DRIFT measurements. The mechanism involves the cleavage of C_α–OH and C_β–O bonds to produce coniferyl alcohol, followed by the removal of γ-OH to generate 4-n-propenyl guaiacol. The effects of some key parameters like solvent, Ru content, temperature, reaction time, and H₂ pressure were also investigated in terms of monophenol yields and average molecular weight. This work provides an economically feasible method for the depolymerization of lignin into highly valuable monophenols.

Hydrocracking of plastics over bifunctional hierarchical zeolites is promising for the upcycling of plastics into value-added products. However, the exact role of their acidic and textural properties toward the catalytic activity remains unclear. Herein, we modified the structure of a β zeolite via dealumination and desilication routes, resulting in hierarchical zeolites. The parent and hierarchical modified β zeolite samples were loaded with Ni and studied for the hydrocracking of virgin HDPE. In comparison to the parent and dealuminated β zeolite, desilicated β zeolite showed a higher conversion of 87.8% with 66.7% of the products in the gasoline range, owing to its significantly high textural properties. The conversion and selectivity of gasoline-range hydrocarbons over the desilicated zeolite were further improved to 95.9 and 69.2%, respectively, by Ni addition. To unlock the structure–activity correlation of the various zeolite samples, the role of different activity-driven factors was studied, resulting in an empirical relationship that aligns with the observed conversions over different zeolite samples. Moreover, it was observed that it is possible to achieve high selectivity of iso-paraffins in gasoline-range hydrocarbons via the optimization of the balance between metal-acid sites on bifunctional hierarchical zeolites. Furthermore, both Ni-loaded hierarchical β zeolites showed good stability and the ability to be regenerated under cyclic runs. The best-performing Ni-loaded desilicated β zeolite was also maintained over various postconsumer waste plastics (conversion = 85–95%) and when using a mixture of postconsumer waste plastics (88.4%). A life cycle assessment and a comparison with the recent literature also demonstrated the advantages of the proposed hierarchical modification routes in achieving high gasoline productivity (6.6–7.6 g_gasoline/g_cat·h) and less environmental impact. Overall, these findings highlight the role of improved textural properties of noble-metal-free, easily modifiable, and environmentally friendly bifunctional hierarchical β zeolites for the enhanced conversion of waste plastics into liquid fuels.

Heterogeneous catalysis over single-atom catalysts (SACs) has garnered significant attention in biomass-derived platform chemical conversion owing to the high atomic utilization and reliable selectivity/stability. Herein, Co single-atom catalysts (Co–N/F1) derived from fractionated lignin were employed for the oriented oxidation of 5-hydroxymethylfurfural (HMF), a typical platform chemical derived from glucose, into 2,5-furandicarboxylicacid (FDCA) under mild conditions. The Co–N/F1 with enhanced Co content was obtained using the low-molecular-weight lignin fraction (F1) with high functional group contents (e.g., Ph–OH and COOH), and the as-prepared catalyst was demonstrated to present a Co–N₄ configuration. Owing to the absence of colored byproduct formation from HMF at elevated temperatures, Co–N/F1 realized the highly selective conversion of HMF to FDCA (100% HMF conversion, 99.20% FDCA yield) under mild conditions (65 °C, 3 bar O₂), which outperformed most reported non-noble metal-supported catalysts. Density functional theory calculations indicate that the Co–N₄ site in Co–N/F1 facilitates the dehydrogenation of the α-C position on HMF and its aldehyde intermediates, resulting in a significantly enhanced catalytic efficiency. Furthermore, Co–N/F1 exhibited stable reusability due to the alkaline resistance of the Co–N₄ structure. Our study details the insights into the synthesis of Co-SACs using a lignin fractionation strategy and further demonstrates its good feasibility for the oriented conversion of biomass-derived platform chemicals under mild conditions.

A photoexcited palladium-catalyzed synthesis of chiral allenes from alkynes via a sequence of isomerization and deracemization is disclosed. This method offers an efficient and cost-effective approach to produce a wide range of chiral allenes with good enantioselectivities and yields (up to 98% yield and 99% ee). The use of readily available and stable alkynes as starting materials simplifies experimental procedures and broadens the scope of the chiral allene synthesis. DBU plays a crucial dual role in this reaction to effectively facilitate the isomerization of alkynes to allenes and enhance the palladium-catalyzed deracemization under visible light excitation, both of which are vital for the success of the process.

Hydrolytic enzymes, such as lactamases or hydantoinases, can be valuably applied to convert lactams (cyclic amides) and cyclic imides into optically pure compounds, for example, d- or l- amino acids, and to resolve racemic mixtures, such as Vince lactams. The chiral building blocks can be utilized to produce biologically active peptides, pesticides, sweeteners, and antibiotics, such as semisynthetic penicillins or cephalosporins. Furthermore, these compounds find application as feed and food additives and constitute useful intermediates for cosmetics, pharmaceuticals, or agrochemicals. Beyond their application in chemical synthesis, cyclic amide and imide hydrolyzing enzymes hold promise in the recovery of materials containing polyamides or in the bioremediation of antibiotics and herbicides. Today, lactam and cyclic imide hydrolyzing biocatalysts mainly originate from enzyme families associated with two distinct structural archetypes: (a) α/β-hydrolases (e.g., lipases) and (b) metal-dependent amidohydrolases (e.g., dihydropyrimidinases/hydantoinases). Beyond these well-explored sources, nature offers an additional wealth of mechanistically, catalytically, and structurally distinct enzymes for lactam and cyclic imide hydrolysis, including serine and metallo-β-lactamases, allantoinases, 5-oxoprolinases, and members of the amidase signature family. To facilitate the discovery of suitable biocatalysts for such types of hydrolysis reactions, we provide a comprehensive overview of application examples, as well as functional annotations (EC identifiers) and structural architectures (CATH identifiers), of the currently known biocatalytic toolbox. In addition, a protein sequence database containing all relevant biocatalyst superfamilies for cyclic amide and imide hydrolysis has been created (https://github.com/ccbiozhaw/CyclAmidImid).

Catalysis is an eternal theme in chemical research because it is indispensable in the chemical industry. Homogeneous and heterogeneous catalysts possess their individual advantages and disadvantages, which are significantly complementary. Therefore, it is highly desirable to develop an effective and practical method for merging the benefits of homogeneous and heterogeneous catalysis. Recently, the application of organic ligands to modify heterogeneous supported catalysts has emerged as an important method to combine the advantages of heterogeneous catalysis with those of homogeneous catalysis. Ligands modified supported catalysts offer the potential to overcome major challenges in tunability and stability for supported catalysts. This Viewpoint discusses the recent progress in the synthesis and application of ligand modified supported metal catalysts in organic reactions that merge the advantages of homo- and heterogeneous catalysis. We discuss the preparation and characterization, the origin of enhanced activities, and the structure–activity relationship of ligand modified supported metal catalysts. The challenges and perspectives for future progress in this field will be given. This viewpoint provides important insights into the development of well-defined heterogeneous catalysts for integrating homogeneous and heterogeneous catalysis.