Silver triflate and triphenylphosphine co-catalyzed reactions of 2-alkynylbenzaldehyde, amine, and α,β-unsaturated ketone

A two-component activation system that combines metal catalysis (AgOTf) and the employment of catalytic amount of organocatalyst (PPh₃) has been successfully employed in the three-component reaction of 2-alkynylbenzaldehyde, amine, and α,β-unsaturated ketone. This reaction proceeds smoothly in THF under mild conditions leading to the functionalized 1,2-dihydroisoquinolines in moderate to good yields.     

Integrated Photochromic-Photothermal Processes for Catalytic Plastic Upcycling

Incorporating high-energy ultraviolet (UV) photons into photothermal catalytic processes may enable photothermal-photochemical synergistic catalysis, which represents a transformative technology for waste plastic recycling. The major challenge is avoiding side reactions and by-products caused by these energetic photons. Here, we break through the limitation of the existing photothermal conversion mechanism and propose a photochromic-photothermal catalytic system based on polyol-ligated TiO₂ nanocrystals. Upon UV or sunlight irradiation, the chemically bonded polyols can rapidly capture holes generated by TiO₂, enabling photogenerated electrons to reduce Ti⁴⁺ to Ti³⁺ and produce oxygen vacancies. The resulting abundant defect energy levels boost sunlight-to-heat conversion efficiency, and simultaneously the oxygen vacancies facilitate polyester glycolysis by activating the nucleophilic addition-elimination process. As a result, compared to commercial TiO₂ (P25), we achieve 6-fold and 12.2-fold performance enhancements under thermal and photothermal conditions, respectively, while maintaining high selectivity to high-valued monomers. This paradigm-shift strategy directs energetic UV photons for activating catalysts and avoids their interaction with reactants, opening the possibility of substantially elevating the efficiency of more solar-driven catalysis.     

Urea-Functionalized Fe4L6 Cages for Supramolecular Gold Catalyst Encapsulation to Control Substrate Activation Modes

The excellent catalytic performances of enzymes in terms of activity and selectivity are an inspiration for synthetic chemists and this has resulted in the development of synthetic containers for supramolecular catalysis. In such containers the local environment and pre-organization of catalysts and substrates leads to control of the activity and selectivity of the catalyst. Herein we report a supramolecular strategy to encapsulate single catalysts in a urea-functionalized Fe₄L₆ cage, which can co-encapsulate a functionalized urea substrate through hydrogen bonding. Distinguished selectivity is obtained, imposed by the cage as site isolation only allows catalysis through π activation of the substrate and as a result the selectivity is independent of catalyst concentration. The encapsulated catalyst is more active than the free analogue, an effect that can be ascribed to transitionstate stabilization rather than substrate pre-organization, as revealed by the MM kinetic data. The simple strategy reported here is expected to be of general use in many reactions, for which the catalyst can be functionalized with a sulfonate group required for encapsulation.     

Neuroprotective Bioorthogonal Catalysis in Mitochondria Using Protein-Integrated Hydrogen-Bonded Organic Frameworks

Mitochondria-targeted bioorthogonal catalysis holds promise for controlling cell function precisely, yet achieving selective and efficient chemical reactions within organelles is challenging. In this study, we introduce a new strategy using protein-integrated hydrogen-bonded organic frameworks (HOFs) to enable synergistic bioorthogonal chemical catalysis and enzymatic catalysis within mitochondria. Utilizing catalytically active tris(4,4′-dicarboxylicacid-2,2′-bipyridyl) ruthenium(II) to self-assemble with [1,1′-biphenyl]-4,4′-biscarboximidamide, we synthesized nanoscale RuB-HOFs that exhibit high photocatalytic reduction activity. Notably, RuB-HOFs efficiently enter cells and preferentially localize to mitochondria, where they facilitate bioorthogonal photoreduction reactions. Moreover, we show that RuB-HOFs encapsulating catalase can produce hydrogen sulfide (H₂S) in mitochondria through photocatalytic reduction of pro-H₂S and degrade hydrogen peroxide through enzymatic catalysis simultaneously, offering a significant neuroprotective effect against oxidative stress. Our findings not only introduce a versatile chemical toolset for mitochondria-targeted bioorthogonal catalysis for prodrug activation but also pave the way for potential therapeutic applications in treating diseases related to cellular oxidative stress.     

Atomic Insights into Synergistic Nitroarene Hydrogenation over Nanodiamond-Supported Pt1−Fe1 Dual-Single-Atom Catalyst

Fundamental understanding of the synergistic effect of bimetallic catalysts is of extreme significance in heterogeneous catalysis, but a great challenge lies in the precise construction of uniform dual-metal sites. Here, we develop a novel method for constructing Pt₁−Fe₁/ND dual-single-atom catalyst, by anchoring Pt single atoms on Fe₁−N₄ sites decorating a nanodiamond (ND) surface. Using this catalyst, the synergy of nitroarenes selective hydrogenation is revealed. In detail, hydrogen is activated on the Pt₁−Fe₁ dual site and the nitro group is strongly adsorbed on the Fe₁ site via a vertical configuration for subsequent hydrogenation. Such synergistic effect decreases the activation energy and results in an unprecedented catalytic performance (3.1 s⁻¹ turnover frequency, ca. 100 % selectivity, 24 types of substrates). Our findings advance the applications of dual-single-atom catalysts in selective hydrogenations and open up a new way to explore the nature of synergistic catalysis at the atomic level.     

The catalytic olefination reaction of aldehydes and ketones with CBr3CF3

The new approach of catalytic olefination reaction (COR) has been used to convert aromatic and aliphatic aldehydes and ketones to 2-bromo-3,3,3-trifluoroprop-1-enes by the treatment of corresponding hydrazones with CBr₃CF₃ under copper(I) catalysis conditions. The reaction proceeds stereoselectively, the target alkenes were obtained in good yields.     

Manganese/Cobalt Bimetallic Relay Catalysis for Divergent Dehydrogenative Difluoroalkylation of Alkenes

The involvement of manganese radical for halogen atom transfer (XAT) reactions has been esteemed as one reliable method but encountered with limited catalytic models. In this paper, a novel bimetallic relay catalysis of Mn₂(CO)₁₀ and cobaloxime has been developed for divergent dehydrogenative difluoroalkylation of alkenes using commercially available difluoroalkyl bromides. A wide range of structurally diverse terminal, cyclic and internal alkenes as well as tetrasubstituted alkenes are found to be good coupling partners to deliver difluoroalkylated allylic products and difluoromethylated cyclic products, accompanied with the production of H₂ as the by-product. This bimetallic relay strategy features broad substrate scope, mild reaction conditions and excellent functional group compatibility. Its success represents an important step-forward to expedite the construction of a rich library of difluoroalkylated products.     

Organocatalytic Enantioselective Protonation for Photoreduction of Activated Ketones and Ketimines Induced by Visible Light

The first catalytic asymmetric photoreduction of 1,2‐diketones and α‐keto ketimines under visible light irradiation is reported. A transition‐metal‐free synergistic catalysis platform harnessing dicyanopyrazine‐derived chromophore (DPZ) as the photoredox catalyst and a non‐covalent chiral organocatalyst is effective for these transformations. With the flexible use of a chiral Brønsted acid or base in H⁺ transfer interchange to control the elusive enantioselective protonation, a variety of chiral α‐hydroxy ketones and α‐amino ketones were obtained with high yields and enantioselectivities.     

Bidirectional Tandem Electrocatalysis Manipulated Sulfur Speciation Pathway for High-Capacity and Stable Na-S Battery

The sluggish polysulfide redox kinetics and the uncontrollable sulfur speciation pathway, leading to serious shuttling effect and high activation barrier associated with sulfur cathode. We describe here the use of core–shell structured composite matrixes containing abundant catalytic sites for nearly fully reversible cycling of sulfur cathodes for Na-S batteries. The bidirectional tandem electrocatalysis provide successive reversible conversion of both long- and short-chain polysulfides, whereas Fe₂O₃ accelerates Na₂S₈/Na₂S₆ to Na₂S₄ conversion and the redox-active Fe(CN)₆⁴⁻-doped polypyrrole shell catalyzes Na₂S₄ reduction to Na₂S. The electrochemically reactive Na₂S can be readily charged back to sulfur with minimal overpotential. Simultaneously, stable cycling of Na-S pouch cell with a high reversible capacity of 696 mAh g⁻¹ is also demonstrated. The bidirectional confined tandem catalysis renders the manipulation of sulfur redox electrochemistry for practical Na-S cells.     

Rhodium-Catalyzed Regio- and Diastereoselective [3+2] Cycloaddition of gem-Difluorinated Cyclopropanes with Internal Olefins

Direct synthesis of gem-difluorinated carbocyclic molecules represents a longstanding challenge in organic chemistry. Herein, a Rh-catalyzed [3+2] cycloaddition reaction between readily available gem-difluorinated cyclopropanes (gem-DFCPs) and internal olefins has been developed, enabling the efficient synthesis of gem-difluorinated cyclopentanes with good functional group compatibility, excellent regioselectivity and good diastereoselectivity. The resulting gem-difluorinated products can undergo downstream transformations to access various mono-fluorinated cyclopentenes and cyclopentanes. This reaction demonstrates the use of gem-DFCPs as a type of “CF₂” C3 synthon for cycloaddition under transition metal catalysis, which provides potential strategy for synthesizing other gem-difluorinated carbocyclic molecules.     

Generation and Stabilization of a Dinickel Catalyst in a Metal-Organic Framework for Selective Hydrogenation Reactions

Although many monometallic active sites have been installed in metal–organic frameworks (MOFs) for catalytic reactions, there are no effective strategies to generate bimetallic catalysts in MOFs. Here we report the synthesis of a robust, efficient, and reusable MOF catalyst, MOF-NiH, by adaptively generating and stabilizing dinickel active sites using the bipyridine groups in MOF-253 with the formula of Al(OH)(2,2′-bipyridine-5,5′-dicarboxylate) for Z-selective semihydrogenation of alkynes and selective hydrogenation of C=C bonds in α,β-unsaturated aldehydes and ketones. Spectroscopic studies established the dinickel complex (bpy⋅⁻)Ni^II(μ₂-H)₂Ni^II(bpy⋅⁻) as the active catalyst. MOF-NiH efficiently catalyzed selective hydrogenation reactions with turnover numbers of up to 192 and could be used in five cycles of hydrogenation reactions without catalyst leaching or significant decrease of catalytic activities. The present work uncovers a synthetic strategy toward solution-inaccessible Earth-abundant bimetallic MOF catalysts for sustainable catalysis.     

Synergistic Catalysis: Enantioselective Addition of Alkylbenzoxazoles to Enals

A novel catalytic enantioselective methodology based on synergistic catalysis is reported. The strategy involves: 1) the metal‐Lewis‐acid activation of alkylazaarenes, and 2) the secondary‐amine activation of enals. Consequently, highly functionalized chiral alkylazaarenes were obtained in good yields and with reasonable stereoselectivity.     

Rare-Earth Catalyzed C−H Bond Alumination of Terminal Alkynes

Organoaluminum reagents’ application in catalytic C−H bond functionalization is limited by competitive side reactions, such as carboalumination and hydroalumination. Herein, rare-earth tetramethylaluminate complexes are shown to catalyze the exclusive C−H bond metalation of terminal alkynes with the commodity reagents trimethyl-, triethyl-, and triisobutylaluminum. Kinetic experiments probing alkyl-group exchange between rare-earth aluminates and trialkylaluminum, C−H bond metalation of alkynes, and catalytic conversions reveal distinct pathways of catalytic aluminations with triethylaluminum versus trimethylaluminum. Most significantly, kinetic data point to reversible formation of a unique [Ln](AlR₄)₂⋅AlR₃ adduct, followed by turnover-limiting alkyne metalation. That is, C−H bond activation occurs from a more associated organometallic species, rather than the expected coordinatively unsaturated species. These mechanistic conclusions allude to a new general strategy for catalytic C−H bond alumination that make use of highly electrophilic metal catalysts.     

Synergistic Diastereo‐ and Enantioselective Functionalization of Unactivated Alkyl Quinolines with α,β‐Unsaturated Aldehydes

A novel alkyl functionalization of unactivated alkyl quinolines has been developed combining InCl₃ activation with organocatalytic activation of α,β‐unsaturated aldehydes in a synergistic fashion. The reaction proceeds in a highly stereoselective manner as a sequence involving two consecutive synergistic catalytic cycles (Lewis acid‐ and iminium ion‐catalyzed) and requires neither pre‐activated alkyl quinoline substrates with electron‐withdrawing substituents nor highly activated electrophiles. The reaction provides selectively double‐ or mono‐addition products in good yields and high to excellent stereoselectivities. Furthermore, based on spectroscopic and labelling experiments, the mechanisms for the reactions are discussed.     

Combined Transition‐Metal‐ and Organocatalysis: An Atom Economic C3 Homologation of Alkenes to Carbonyl and Carboxylic Compounds

A combination of regioselective room‐temperature/ambient‐pressure hydroformylation (transition‐metal catalysis) and decarboxylative Knoevenagel reactions (organocatalysis) allowed for the development of an efficient, one‐pot C3 homologation of terminal alkenes to (E)‐α,β‐unsaturated acids and esters, (E)‐β,γ‐unsaturated acids, (E)‐α‐cyano acrylic acids, and α,β‐unsaturated nitriles. All reactions proceed under mild conditions, tolerate a variety of functional groups, and furnish unsaturated carbonyl compounds in good yields and with excellent regio‐ and stereocontrol. Further, an iterative C2 homologation of (E)‐α,β‐unsaturated carboxylic acids is possible through a combination of decarboxylative hydroformylation employing a supramolecular catalyst followed by decarboxylative Knoevenagel condensation with an organocatalyst.     

Carbon Dioxide as an Alternative C1 Synthetic Unit: Activation by Transition-Metal Complexes

The carbon dioxide molecule has been of limited importance as a synthetic unit in organic chemistry. When it is coordinated to transition metals, however, completely new possibilities arise; CO₂ can bond to metal complexes in a variety of ways and can enter into insertion and coupling reactions, or become catalytically attached to other substrates. The formation of C? C bonds between carbon dioxide and unsaturated hydrocarbons under conditions of homogeneous catalysis makes available new synthetic routes to industrially interesting organic compounds.     

Two novel heterobimetallic metal-organic frameworks for the enhanced catalytic thermolysis and laser ignition of CL-20

The study of multiple complex catalytic mechanisms is currently one of the great scientific issues for the application of high-energy solid propellants. Two novel heterobimetallic metal-organic frameworks (MOFs), Ba₄Pb₄(CH₃CO₂)₈ [(CH₆CO₂)₄Pb](CH₃CO₂)₄ (PbBa-MOF) and Ba₂Ni(CO₂H)₆(OH₂)₄ (NiBa-MOF), were prepared via the solvothermal method, and their structures and composition were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR) techniques and N₂ adsorption/desorption experiment. The thermal decomposition characteristics of the two MOFs and their catalytic performances on the hexanitro hexaazaisowurtzitane (CL-20) thermolysis were also studied by differential scanning calorimetr (DSC) and thermogravimetric-fourier transform infrared spectroscopy-mass spectrum (TG-FTIR-MS) methods. The results showed that the NiBa-MOF presented a lower initial decomposition temperature than the PbBa-MOF, and the difference of the MOFs structures affected the starting point of thermal decomposition. Compared with the pure CL-20, the thermolysis peak temperature and apparent activation energy (E_a) of the CL-20/PbBa-MOF mixture were decreased by 2.2 °C and 23.76 kJ?mol^?1, respectively. The E_a of CL-20/NiBa-MOF mixture was lower and 42.01 kJ?mol^?1, indicating the better catalytic activity of NiBa-MOF. The thermolysis catalytic mechanisms were studied by analyzing the transformation of gas products during the pyrolysis of mixtures. The effect of these two MOFs on the CL-20 thermolysis is primarily owing to the strong attraction of metal cations to electronics, bimetallic synergistic catalysis, and the release of active free radicals. Furthermore, the laser ignition and flame propagation features showed that these two MOFs reduced the minimum ignition power density and ignition delay time of the CL-20, and the flame becomes brighter and more luminous. The influence of the two MOFs on the flame bright spot of CL-20 based mixtures was described.     

Recent advances in gold-complex and chiral organocatalyst cooperative catalysis for asymmetric alkyne functionalization

Homogeneous gold catalysis has demonstrated the preponderant capability of realizing a broad range of synthetically versatile alkyne functionalization over the last two decades. Though catalytic asymmetric alkyne transformation has focused on the principle of using gold catalysts either associated with chiral phosphine ligand or combined with chiral counterion, a variety of breakthroughs have been reported with the application of gold-complex and chiral organocatalyst cooperative catalysis strategy, which could enable the challenging transformations that cannot be realized by mono-catalysis with excellent stereoselectivity. This review will cover two general protocols in this field, including relay catalysis and synergistic catalysis, with emphasis on the detailed cooperative catalysts models to illustrate the roles of the two catalysts and highlight the potential synthetic opportunities offered by asymmetric cooperative catalysis.     

Copper-catalyzed oxidative coupling of carboxylic acids with formamides for the synthesis of α,β-unsaturated amides

A novel and efficient protocol for the synthesis of α,β-unsaturated amides has been developed using catalytic amount of Cu(OAc)₂ and TBHP as an available oxidant. Oxidative coupling of various unsaturated carboxylic acids with N,N-disubstituted formamides was examined to furnish the desired products in good yields.     

A Compartmentalized Nanoreactor Formed by Interfacial Hydrogelation for Cascade Enzyme Catalytic Therapy

Some cellular enzymatic pathways are located within a single organelle, while most others involve enzymes that are located within multiple compartmentalized cellular organelles to realize the efficient multi-step enzymatic process. Herein, bioinspired by enzyme-mediated biosynthesis and biochemical defense, a compartmented nanoreactor (Burr-NCs@Gl^SOD) was constructed through a self-confined catalysis strategy with burr defect-engineered molybdenum disulfide/Prussian blue analogues (MoS₂/PBA) and an interfacial diffusion-controlled hydrogel network. The specific catalytic mechanism of the laccase-like superactivity induced hydrogelation and cascade enzyme catalytic therapy were explored. The confined hydrogelation strategy introduces a versatile means for nanointerface functionalization and provides insight into biological construction of simulated enzymes with comparable activity and also the specificity to natural enzymes.