Catalytic System Research Articles

Hydroalkylation of unactivated olefins with C(sp3)─H compounds enabled by NiH-catalyzed radical relay.

The hydroalkylation reaction of olefins with alkanes is a highly desirable synthetic transformation toward the construction of C(sp3)─C(sp3) bonds. However, such transformation has proven to be challenging for unactivated olefins, particularly when the substrates lack directing groups or acidic C(sp3)─H bonds. Here, we address this challenge by merging NiH-catalyzed radical relay strategy with a HAT (hydrogen atom transfer) process. In this catalytic system, a nucleophilic alkyl radical is generated from a C(sp3)─H compound in the presence of a HAT promotor, which couples with an alkyl metallic intermediate generated from the olefin substrate with a NiH catalyst to form the C(sp3)─C(sp3) bond. Starting from easily available materials, the reaction not only demonstrates wide functional group compatibility but also provides hydroalkylation products with regiodivergence and excellent enantioselectivity through effective catalyst control under mild conditions.

Fischer-Speier Esterification and Beyond: Recent Mechanicistic Advances

Over the past 130 years, Fischer-Speier esterification has been established as the benchmark method for synthesizing esters from organic acids and alcohols. The reaction’s versatility, arising from the vast combinations of starting materials and the numerous catalytic alternatives to the traditional H2SO4, has maintained its relevance, with a steady flow of publications addressing new developments. This review highlights the most significant contributions to Fischer-Speier esterification over the past five years, with a particular emphasis on mechanistic advancements and innovative catalytic systems. Both homogeneous and heterogeneous catalytic approaches are discussed, including novel catalysts leveraging hydrogen-bonding interactions and systems offering fresh insights into specific reaction mechanisms and atypical methodologies. Some of these catalytic systems, as ionic liquids or sulfonated heterogeneous catalytic precursors, reached excellent yields (>90%), e.g., in the synthesis of fatty acids methyl esters. Also, classic catalysts such as H2SO4 and para-toluen sulfonic acid were optimized for quantitative conversions (e.g., in the esterification of trans-cinnamic acid with methanol). A consistent number of catalysts was studied with model substrates (as benzoic acid in combination with methanol, ethanol, and ethylene glycol), and new activation pathways were presented.

Chemocatalytic Conversion of Dinitrogen to Ammonia Mediated by a Tungsten Complex

Whereas molybdenum dinitrogen complexes have played a major role as catalytic model systems of nitrogenase, corresponding tungsten complexes were in most cases found to be catalytically inactive. Herein, we present a modified pentadentate tetrapodal (pentaPod) phosphine ligand in which two dimethylphosphine groups of the pentaPodMe (P5Me) ligand have been replaced with phospholanes (Pln). The derived molybdenum complex [Mo(N2)P5Pln] generates 22 and the analogous tungsten complex [W(N2)P5Pln] 7 equivalents of NH3 from N2 in the presence of 180 equiv.s of SmI2(thf)2/H2O, rendering the latter the first tungsten complex chemocatalytically converting N2 to NH3. In contrast, the tungsten complex [W(N2)P5Me] generates ammonia from N2 only in a slightly overstoichiometric fashion. The reasons for these reactivity differences are investigated with the help of spectroscopic and electrochemical methods.

Palladium-Catalyzed Ortho-Alkylation of Iodoarenes Enabled by a Cooperative Cycloolefin Ligand and a Bulky Trialkylphosphine

We recently achieved ortho-alkylation of iodoarenes utilizing a dual-ligand catalytic system that effectively combines palladium/olefin ligand cooperative catalysis with reversible C(sp²)−I reductive elimination enabled by a bulky trialkylphosphine ligand. Through careful mechanistic investigations, we confirmed the compatibility of the crucial steps involved in this process by isolating key organometallic intermediates and studying their stoichiometry transformations. Utilizing this protocol, we successfully achieved the ortho-alkylation of a variety of iodoarene substrates, thereby expanding the scope of applications for Catellani-type reactions. This study showcases the synthetic potential of the Pd/olefin ligand cooperative system as an innovative complement to established Pd/NBE catalysis. In this Synpacts article, we present the conceptual framework underpinning this reaction and detail the key aspects of its development. 1Introduction 2Research Background 2.1The Catellani Reaction: Pd/Norbornene Catalysis 2.2Cooperative Cycloolefin Ligands for the Catellani-Type Reactions 2.3C-X Reductive Elimination on Pd Center 3Development of the Reaction 3.1Proof-of-Concept by Stoichiometric Reactions 3.2Substrate Scope and Synthetic Applications 4Conclusion

Recent Applications of the Sonogashira Reaction in the Synthesis of Drugs and Their Derivatives: A Review

ABSTRACTMetal‐catalyzed cross‐coupling reactions are essential tools for constructing C–C bonds in organic synthesis. Among these prominent approaches, the Sonogashira reaction stands out as a key player and is widely utilized in medicinal chemistry. This versatile method enables the creation of complex C (sp2)–C (sp) bonds by linking aryl or vinyl halides with terminal alkynes, facilitating the efficient construction of molecular structures crucial for drug development. A notable application of the Sonogashira reaction is its ability to incorporate aromatic and alkynyl functionalities into pharmaceutical compounds. Depending on the impactful catalytic system evolved gradually, the Sonogashira reaction can involve either double‐metal catalysis or single‐metal catalysis. This review sheds light on the diverse applications of the Sonogashira coupling approach in drug synthesis and the generation of their derivatives.

Ambient Synthesis of Cyclohexanone Oxime via In Situ Produced Hydrogen Peroxide over Cobalt-Based Electrocatalyst.

Cyclohexanone oxime, a critical precursor for nylon-6 production, is traditionally synthesized via the hydroxylamine method under industrial harsh conditions. Here is present a one-step electrochemical integrated approach for the efficient production of cyclohexanone oxime under ambient conditions. This approach employed the coupling of in situ electro-synthesized H2O2 over a cobalt (Co)-based electrocatalyst with the titanium silicate-1 (TS-1) heterogeneous catalyst to achieve the cyclohexanone ammoximation process. The cathode electrocatalyst is consisted of atomically dispersed Co sites and small Co nanoparticles co-anchored on carboxylic multi-walled carbon nanotubes (CoSAs/SNPs-OCNTs), which delivered superior electrocatalytic activity toward the two-electron oxygen reduction reaction (2e- ORR) with high-efficient H2O2 production in 0.1m sodium phosphate (NaPi). Theoretical calculations revealed that the introduction of Co nanoparticles effectively optimized the binding strength of *OOH species on Co atomic sites, thus facilitating the 2e- ORR. The subsequent tandem catalytic system achieved a high cyclohexanone conversion of 71.7%±1.1% with a cyclohexanone oxime selectivity of 70.3%±0.6%. In this system, the TS-1 catalyst effectively captured the *OOH intermediate and activated the in situ generated H2O2 to form Ti-OOH species, which promoted the formation of hydroxylamine and thereby enhanced the oxime production performance.

Strong Acid‐Free Homogeneous Catalytic Systems for the Ester Products Synthesis by Alkenes Alkoxycarbonylation: Recent Advances

AbstractAlkoxycarbonylation represents a method for the ester products synthesis from available reagents – unsaturated compounds, alcohols, and CO. The beginning of research on this reaction was laid in W. Reppe’ works in 1953. In early works, halides and carbonyls of Co, Ni, Rh, and Ir were used as catalysts, and alkoxycarbonylation was often complicated by the unsaturated compounds hydroformylation or alcohol carbonylation. In recent decades, in the presence of the most active and selective Pd‐phosphine systems with strong protonic acids, the products are typically only isomeric esters, which corresponds to the creating waste‐free production principles. At present, a large‐capacity synthesis process for methyl methacrylate, dubbed Alpha, is in operation, with the initial stage being ethylene methoxycarbonylation. In light of these developments, there is a growing interest among chemists and technologists in alkenes alkoxycarbonylation. The use of strong protonic acids as co‐catalysts is essential for the formation of active catalytic complexes. However, these acids are highly corrosive and can cause the alkenes isomerisation. This review is devoted to the analysis of acid‐free homogeneous Pd‐, Ru‐, Co‐, and Ni‐catalysts employed in alkenes alkoxycarbonylation over the past 15 years. As a result, polymers, monomers and other valuable linear and branched esters were obtained.

Basic-Functionalized Ionic Porous Organic Polymers: Triple Roles in One for Highly Efficient and Recyclable Carboxylative Cyclization of CO2 under Mild Conditions.

The transformation of carbon dioxide (CO2) into high-value chemicals is a significant step towards achieving the goal of "carbon neutrality". α-methylene cyclic carbonate, as an intermediate for the synthesis of many important organic compounds, is widely employed in industrial productions. In this work, a series of ionic porous organic polymers (IPOPs) with different basic-functionalized anions were successfully synthesized and adjusted to have certain BET surface areas and high contents of ion sites by post-modification. These basic-functionalized IPOPs could exhibit excellent catalytic performance for carboxylative cyclization of CO2 at 30 °C and 1 bar in presence of silver salts, eliminating the use of the extra organic bases. In the whole catalytic reaction, the basic-functionalized anions could play triple roles: enriching CO2 for further transformation, activating the hydroxyl groups of substrates to improve the catalytic performance, while coordinating with Ag atom to stabilize and regenerate catalyst. Notably, the catalytic system of DCX-4-Tet/Ag2O exhibited excellent recyclability, and the yield of α-alkylidene cyclic carbonate was well maintained at 99 % after 5 cycles. To the best of our knowledge, the catalytic system was the first example of basic-functionalized IPOPs that played multiple roles for highly efficient CO2 cyclization under mild conditions without any extra organic bases.

Ruthenium-Catalyzed Carbocycle-Selective Hydrogenation of Fused Heteroarenes.

The homogeneous catalytic hydrogenation of benzo-fused heteroarenes generally provides partially hydrogenated products wherein the heteroaryl ring is preferentially reduced, such as quinoline hydrogenation, leading to 1,2,3,4-tetrahydroquinoline. Herein, we report a carbocycle-selective hydrogenation of fused N-heteroarenes (quinoline, isoquinoline, quinoxaline, etc.) using the Ru complex of a chiral spiroketal-based diphosphine (SKP) as the catalyst, affording the corresponding 5,6,7,8-tetrahydro products in high chemoselectivities. This catalytic system is also effective for the asymmetric carbocycle hydrogenation of fused heteroarenes bearing a boryl or amino group. Experimental studies provided a strong support for the homogeneous nature of the catalysis, and an inner-sphere mechanism was proposed for the hydrogenation. DFT calculations indicated that the hydrogenation is initiated by η4-coordinative activation of quinoline carbocycle to Ru dihydride complex of SKP, followed by metal-to-ligand hydride transfer. Subsequent carbocycle reduction proceeds via consecutive steps of the H2 oxidative addition and C-H reductive elimination.

Non-covalent organocatalyzed enantioselective cyclization reactions of α,β-unsaturated imines.

Asymmetric cycloaddition is a straightforward strategy which enables the synthesis of structurally distinct cyclic derivatives which are difficult to access by other methodologies, using an efficient and atom-economical path from simple precursors. In recent years several asymmetric catalytic cyclization strategies have been accomplished for the construction of N-heterocycles using various catalytic systems such as chiral metal catalysts, chiral Lewis acids or chiral organocatalysts. This review presents an overview of the recent advances in enantioselective cyclization reactions of 1-azadienes catalyzed by non-covalent organocatalysts.

Increasing the dual-enzyme cascade biocatalysis efficiency and stability of metal-organic frameworks via one-step coimmobilization for visual detection of glucose.

In biosensing analysis, the activity of enzyme systems is limited by their fragility, and substrates catalyzed by monoenzymes tend to undergo spontaneous decomposition during ineffective mass transfer processes. In this study, we propose a novel strategy to encapsulate the glucose oxidase and horseradish peroxidase (GOx&HRP) cascade catalytic system within the hydrophilic zeolite imidazole framework ZIF-90. By leveraging the specific pore structure of ZIF-90, we effectively immobilized GOx and HRP molecules in their three-dimensional conformations, which improved the catalytic activity of the encapsulated enzymes compared with that of free GOx and HRP in various harsh environments. Additionally, our strategy reduced the occurrence of ineffective mass transfer and enhanced the sensitivity of the biosensor through an enzyme cascade system. When this biosensor was applied to serum samples containing complex biological matrices, the degradation of GOx&HRP by various proteases and the surface adsorption of diverse biomolecules were effectively prevented, thereby generating stable and reliable signals of glucose levels. The sensor shows remarkable sensitivity and selectivity for determining glucose concentrations ranging from 0 to 2.5 μg ml-1, with a detection limit as low as 0.034 μg ml-1. Furthermore, we developed a paper-based colorimetric sensor utilizing GOx&HRP@ZIF-90 integrated with a smartphone platform for the visual detection of blood glucose.

Advances in Valorization of Biomass-Derived Glycolic Acid Toward Polyglycolic Acid Production

Glycolic acid (GA) is a versatile two-carbon organic chemical with multiple applications in industry and daily life. Currently, GA production depends heavily on the coal chemical industry. In this context, the sustainable production of GA from renewable resources has garnered significant attention. With the design and development of various catalytic systems, the yield of GA from biomass-based feedstocks has been improved observably. Poly(glycolic acid) (PGA) is an aliphatic polyester that exhibits a unique crystalline structure, excellent gas barrier properties, high mechanical strength, superior biocompatibility, and biodegradability. It has a wide range of applications in various fields, such as medical devices, oil extraction, bottle materials, film materials, and textile materials. This article comprehensively elaborates on the methods for the biomass-based synthesis of glycolic acid, the precursor of polyglycolic acid (PGA), as well as the preparation process of PGA. It fills the research gap regarding the sources of biomass raw materials for polyglycolic acid. Additionally, it delves into various modification strategies for PGA and provides an overview of its current applications in multiple fields, including biomedicine, food packaging materials, oil and gas resource development, and agricultural cultivation. The purpose of this article is to provide comprehensive reference information on the synthesis techniques, modification methods, and practical applications of PGA. Furthermore, it offers guidance for research on biodegradable plastics and the biomass-based synthesis of glycolic acid.

INFRARED SPECTROSCOPIC ANALYSIS OF COMPLEX COPPER(II) CONTAINING CATALYTIC SYSTEM

The synthesized 2 individual orthophosphate catalysts AlPO4 and Cu3(PO4)2 and 7 new complex aluminum-copper (II) orthophosphate catalytic systems of the type xAlPO4·yCu3(PO4)2 was obtained based on them were investigated by the method of IR spectroscopic analysis. At the same time, the content of both orthophosphates in the catalyst structure varies in the range of 0.5 - 99.5 wt. %. In the entire series of air-dry samples and those baked at the optimal heat treatment temperature (600 °С), the frequencies and intensities of the absorption bands of the IR spectra of the obtained catalytic systems of the type type xAlPO4·yCu3(PO4)2 are characterized by intense absorption in the region of valence vibrations of OH groups of water molecules (3610‒3005 cm-1). Valence vibrations of OH groups of water molecules, which take a direct part in the formation of hydrogen bonds, are observed in the region of 2380‒1880 cm-1. Characteristic manifestations of the hydrogen bond in the vibrational spectrum of H2O, which is part of the structure of the synthesized aluminum-copper (II) orthophosphate catalysts, are a low-frequency shift, an increase in intensity, and a broadening of the bands of valence vibrations of its OH groups. At the same time, in the region 1114‒400 cm-1, valence and deformation vibrations of the orthophosphate ion PO43- are observed, which are clearly expressed in the form of clear absorption bands in the dehydration products for all synthesized binary catalytic systems. Additional coordination of the orthophosphate anion with metal cations Al3+ and Сu2+ is observed. Heating all synthesized orthophosphate samples above 700 °С contributes to their complete dehydration and the emergence of IR spectra characteristic of anhydrous orthophosphate salts.

SYNTHESIS AND RESEARCH OF THE CATALYTIC SYSTEM xAlPO4 . yCu3(PO4)2

Individual orthophosphate catalysts AlPO4 and Cu3(PO4)2 were synthesized. A new synthesis technique was developed and a new complex aluminum-copper (II) orthophosphate catalytic system of the type xAlPO4·yCu3(PO4)2 was obtained based on them (К-1–К-7), which has the predicted physical and chemical properties. The content of both orthophosphates in the catalyst structure varies in the range of 0.5 - 99.5 wt. %. At the final heat treatment temperature (700oC), all synthesized complex catalysts K-1–K-7 are X-ray crystalline. The process of thermal treatment of catalysts contributes to their gradual dehydration and release of water from the structure of the samples, as well as the occurrence of characteristic endothermic effects at the appropriate temperatures. At high temperatures of heat treatment (about 500 oC), the processes of crystallization of the structures are observed on the synthesized samples K-1–K-7. Heating of all samples of a complex catalytic orthophosphate system of the type xAlPO4.yCu3(PO4)2 at temperatures above 700 oC leads to their complete dehydration and the formation of anhydrous salts. It can be predicted that the synthesized new complex oxide catalytic heterogeneous systems of the type xAlPO4.yCu3(PO4)2 have been will show improved both acidic surface properties and catalytic parameters: activity and selectivity in reactions of partial oxidation of n-alkanes to valuable products.

Anaerobic Catalyst Design for Alcohol Oxidation: Fine‐Tuning Copper/TEMPO with Bipyridine Proportions

In this study, we investigate the indirect electro‐oxidation of benzyl alcohol using the Copper/TEMPO catalytic system, which combines copper complexes with 2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPO) in an anaerobic medium. We reexamine the impact of bpy ligand proportions, exploring ratios of 1:1, 2:1, 3:1, and 4:1 on catalytic activity. Cyclic voltammetry and visible spectroscopy reveal distinct electrochemical characteristics and complex formations at different bpy ratios. Simulations uncover intricate energy equilibria involving ion coordination, varying with oxidation state and bpy proportion. Theoretical and experimental spectra align, supporting the proposed structures. The Brønsted base, triethylamine (TEA), essential in this anaerobic system, shows different voltammetric profiles with each ligand ratio, revealing key interactions with bpy complexes. In the presence of benzyl alcohol, the 1:1 and 2:1 ratios exhibit indirect catalytic activity, with the 2:1 ratio yielding significantly higher current densities. This establishes a new optimal condition where [Cu(bpy)₂]²⁺ formed in a 2:1 stoichiometry demonstrates superior activity with a lower redox potential, while maintaining labile coordination points for necessary interactions. Theoretical results also indicate weaker TEMPO coordination to [Cu(bpy)₂]²⁺.

Enhanced catalytic degradation of methylene blue using self-propelled Janus micromotors: An insight into decomposing characteristics of passive and active hematite particles studded with Pt nanoparticles.

Recent advancements in catalytic micromotors have shown significant potential for environmental applications, yet challenges such as particle agglomeration persist. In this study, we compare the degradation of methylene blue using hematite particles fully coated with platinum and those partially decorated with platinum. The selective decoration, confirmed through techniques like EDX, FESEM, TEM, and XPS, plays a crucial role in the micromotors' behavior. The decomposition of hydrogen peroxide (H2O2) by Pt nanoparticles on one side of the hematite particles generates thrust, propelling the micromotors and enhancing their interaction with pollutant molecules. This active mobility helps counteract agglomeration, preventing the formation of irregular 3D clusters and improving catalytic efficiency. Our findings show that partially decorated particles achieve up to 85% dye removal within 90min, outperforming fully decorated particles, which reach only 33% efficiency due to aggregation and sedimentation. These results underscore the importance of optimized surface decoration for improving the performance and stability of catalytic systems in pollutant degradation.

Neodymium‐Mediated Coordinative Chain Transfer Homopolymerization of Bio‐Based Myrcene and Copolymerization With Butadiene and Isoprene

ABSTRACTCoordinative chain transfer polymerization (CCTP) has emerged as a powerful strategy in controlling the polymerization behavior of petroleum‐based diene monomers of butadiene (BD) and isoprene (Ip) and has been extensively studied in the past few years. Nevertheless, for the bio‐based terpene monomer of myrcene (My), its polymerization performance is rarely disclosed. Herein, by using a neodymium‐based Ziegler–Natta catalytic system of Nd(vers)3/Al(i‐Bu)2H/AlEt3/EASC, the CCTP of My was systematically evaluated. In order to concrete the CCTP characteristic, more evidence was provided, including its comprehensive comparison with the Ip system, kinetic studies, and seeding polymerization. All these results have led to the conclusion that, despite the long alkenyl substitute in the My monomer, CCTP properties were still demonstrated, albeit with relative lower chain transfer efficiency. Coordinative chain transfer copolymerization (CCTcoP) of My with BD or Ip was also studied, in which, similar to My homopolymerization, well‐controlled polymerization behaviors were also revealed that gave narrow polydispersities, high atom economies, as well as controlled copolymer compositions. Monomer reactivity ratio studies by Fineman‐Ross plot revealed that, for CCTcoP of My and BD, rMy and rBD were determined as 0.62 and 0.27, whereas for My/Ip system, rMy and rIp values were 0.74 and 0.24, respectively, implying both two systems preferred to undergo cross‐polymerization to give copolymers rather than homopolymer sequences.

Decarboxylative Coupling of Ketoacids with Allylic Acetates.

We developed a novel, metal-free catalytic system for synthesizing a broad range of itaconates using α-ketoacids and allylic acetate. This method, leveraging phosphine and Mes-Acr+(BF4-) catalysts, has proven versatile, enabling the efficient itaconation of peptides, the synthesis of bioactive itaconates, and the preparation of an itaconate-based bio-orthogonal probe.

Ruthenium-Catalyzed α-Regioselective Hydroboration of Allenes.

Hydroboration of allenes is powerful and atom-economic approach to the synthesis of organoboranes, such as the highly versatile allylboranes. However, regarding regiocontrol, existing methods uniformly deliver the boron functionality to the less hindered β- or γ-position, but not the α-position. The latter is particularly challenging for allenes with substantial steric difference between the two terminals and lacking electronic bias (e.g., 1,1-disubstituted allenes). Herein we report the first highly efficient ruthenium-catalyzed hydroboration of allenes featuring exclusive α-regioselectivity, providing access to sterically hindered allyl boranes that are limitedly accessible by conventional methods. DFT studies suggested that the unusual α-regioselectivity is attributed to the disfavored reductive elimination at the γ-position due to the high energy cost required to overcome the agnostic interaction and rotation of the key π-allyl intermediates. This protocol is also applicable to the previously unprecedented α-hydroalkynylation and underdeveloped α-hydrosilylation of allenes, thus complementing known catalytic systems and providing convenient access to highly congested yet densely-functionalized allyl silanes and skipped enynes bearing a fully-substituted allylic carbon center. It is expected that this ruthenium-catalyzed system can serve as a new platform for the development of other hydrofunctionalization processes with unorthodox selectivity.

Photocatalytic CeCl3-Promoted C-H Alkenylation and Alkynylation of Alkanes.

The reemerging field of photoredox catalysis offers numerous advantages towards the development of novel, sustainable and easy-to-execute organic transformations. Herein, we report a light-triggered application of cerium complexes towards the C-H alkenylation and alkynylation of alkanes. An indirect HAT-mediated photocatalytic protocol was developed, using a cerium salt (CeCl3.7H2O) and a chlorine source (TBACl) as the catalytic system. A variety of cyclic and linear hydrocarbons were utilized, delivering the corresponding alkenylation or alkynylation products in good to high yields, displaying high regioselectivity. A series of mechanistic experiments were conducted.