Homogeneous Catalytic System Research Articles

Synthesis of isochromanones and benzoxepinones by palladium catalyzed cyclocarbonylation reactions

Heterocyclic compounds such as lactones, lactams or pyrrolidinones are employed as useful intermediates for the synthesis of biologically active products. In the past decades various preparation routes to these class of heterocycles have been described and palladium-based compounds have been regarded as the most efficient catalysts for the preparation of important cyclic compounds. In this work, novel isochromanome and benzoxepinone derivatives have been prepared and fully characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopies and gas chromatography–mass spectrometry (GC–MS) analysis. An effective homogeneous catalytic system based on palladium complex was used. Isochromanone and benzoxepinone derivatives have been synthesized through selective cyclocarbonylation reactions respectively of 2-vinylbenzylalcohols and 2-alkynylbenzylalcohols under syn-gas condition using Pd(OAc)2-dppb as the catalytic system. Depending on the subtrate, different lactone structures were obtained with a good selectivity for each reaction.

Advances in the homogeneous catalyzed alcohols homologation: The mild side of the Guerbet reaction. A mini-review

The Guerbet reaction would be an optimal solution for bio-ethanol refinery by homologation and it substantially requires the development of active and highly selective catalysts. Although heterogeneous catalysis remains more desirable, homogeneous Guerbet catalytic systems are nowadays acknowledged as challenging proposals for high selectivity and conversion under mild reaction conditions. Several molecular bi-functional catalysts, based on ruthenium, iridium and manganese complexes bearing different ligands such as phosphine, bidentate bisphosphine (P-P) and phosphamine (P-N), pincer (N-N-N), (P-N-P) and cyclopentadienone, are active in the co-presence of a base, which is essential in all the cases for the condensation reaction. This mini-review is aimed to describe the state of the art, with incremental steps forward to understand the role of the catalytic systems and the reaction conditions on conversion and selectivity. While showing different efficiency, mutable behavior by minimal change in the ligand scaffold, variation in water tolerance and only one example of recyclability, metal catalysts are found to be similar in terms of proposed mechanisms. The influence of additives and capability to maintain activity in fermentation broth and bio-ethanol from wine value chain to second generation bio-fuel are also discussed. Although not yet completely rationalized, experimental and theoretical mechanistic investigations pave the way for the design of more stable and efficient catalysts toward improved applicability.

Enhanced Catalytic Activity of TEMPO-Mediated Aerobic Oxidation of Alcohols via Redox-Active Metal-Organic Framework Nodes.

Metal-organic frameworks (MOFs) are outstanding platforms for heterogeneous catalysis due to their tunable pore size, huge surface area, large porosity, and potential active sites. The design and synthesis of MOF/organocatalyst co-catalytic systems have attracted considerable interest owing to their high catalytic activity, low toxicity, and mild reaction conditions. Herein, we reported the synthesis of a bifunctional TEMPO-IsoNTA organocatalyst featuring a pyridyl group as an anchoring site and a TEMPO radical as a catalytic active site. By using the topologically isomorphic structures of MIL-101(Fe) and MIL-101(Cr) as co-catalysts, these MOF/TEMPO-IsoNTA systems enable the efficient aerobic oxidation of various alcohols to their corresponding aldehydes or ketones under mild conditions. Notably, the MIL-101(Fe)/TEMPO-IsoNTA system exhibits superior catalytic activity, thanks to their redox-active FeIII-oxo nodes, which facilitate the regeneration of TEMPO-IsoNTA. Our research not only solves the problem of potential heavy metal contamination in the TEMPO-based homogeneous catalytic system, but also enriches the understanding of synergism of MOFs/organocatalysts.

Aerobic oxidative C-C bond cleavage and functionalization for the synthesis of value-added chemicals.

The aerobic oxidative cleavage of C-C bonds is an attractive and sustainable route for constructing valuable molecules such as esters, nitriles, and amides. Traditionally homogeneous catalytic systems for C-C bond cleavage required harsh conditions, stoichiometric oxidants, and noble metal catalysts to overcome the thermodynamic and kinetic barriers of C-C bonds, imposing environmental concerns of the transformation. Therefore, developing efficient, low-cost, and environmentally benign methods for C-C bond cleavage is of great importance and a cutting-edge area in modern chemistry. This feature article summarizes the sustainable aerobic oxidative C-C bond cleavage method developed by our group in the past 5 years. Fundamental principles in catalyst design, substrate scope, and mechanism for C-C bond cleavage are also discussed.

Recent Advances in Homogeneous Catalytic Systems for CO2 Hydrosilylation and Related Transformations

Recent Advances in Homogeneous Catalytic Systems for CO₂Hydrosilylation and Related Transformations

Selective catalytic synthesis of new terpenic chlorides using NaDCC as an eco-friendly and highly stable FAC agent.

A simple, mild and efficient scope pathway for a selective catalytic chlorination of terpenic olefins is investigated in the presence of a highly efficient chlorination agent and a readily available Lewis acid catalyst. The sodium dichloroisocyanurate (NaDCC) used in the present work as an easy handling, sustainable and cost-effective chlorine donor due to its high free available chlorine (FAC), exhibits a high efficiency for selective catalytic chlorination. Herein, we report for the first-time the FeCl2/NaDCC combination system for the selective catalytic chlorination towards new functionalized terpenic olefins. In order to examine the general features of this catalytic reaction, the effects of pH, solvent, dilution, chlorination agent nature, stoichiometry and reaction kinetics are optimized using carvone as a model substrate. Among the studied parameters, catalyst stoichiometry was found to be determinant for highly controllable chlorination selectivity towards new allylic and vinylic chlorides. Indeed, the oxidation state, ligand and metal effects of the catalyst are examined using various Lewis acids, where the chlorinated ones (MClx), such as FeCl2, FeCl3 and SnCl2, exhibit a comprehensive approach for a controllable chlorination reaction. In addition, the homogeneous catalytic system shows good reusability with significant catalytic conversion depending on the FAC content in the reaction medium. The reaction proceeds under mild conditions with shorter reaction time and high selectivity towards new high added value allylic and vinylic chlorinated derivatives of naturally occurring terpenic olefins in good to excellent yields.

Nucleophilic substitution reaction as an important tool in the synthetic protocol for selenium donor containing Schiff bases: applications of metal complexes in homogeneous catalysis

Nucleophilic substitution reaction has been used as a tool to incorporate Se in ligands having imine functionality. Metal complexes of such ligands,i.e., Schiff bases, are used as homogeneous catalytic systems for a variety of organic reactions.

Unprecedented Mechanical Properties in Linear UHMWPE Using a Heterogeneous Catalytic System

Several homogeneous postmetallocene complexes are known to produce weakly entangled ultrahigh-molecular-weight polyethylene (disentangled UHMWPE) under controlled polymerization conditions leading to ultimate mechanical properties. Major challenges in using a homogeneous catalyst system exist such as reactor fouling and uncontrolled polymer morphology, which could be addressed by heterogenization of the single-site complex. In such a scenario, a heterogeneous catalytic system that can synthesize ultrahigh-molecular-weight polyethylene with a reduced number of entanglements, to an extent that the mechanical properties are equivalent to those obtained using a postmetallocene catalyst in a homogeneous condition, remains a challenge. Herein, a magnesium chloride based in situ formed activator/support, MgClx/EtnAly(2-ethyl-1-hexoxide)z, is employed with a highly active bis[N-(3-tert-butylsalicylidene)pentafluoroanilinato] titanium(IV) dichloride (Cat. 1) for the synthesis of ultrahigh-molecular-weight polyethylene with a reduced number of entanglements. A novel route is adopted to make a nano-support that allows tailoring of the entangled state and control over the resultant morphology without reactor fouling and wall sheeting, thus providing the feasibility of pursuing the polymerization via a continuous process. The synthesized nascent polymer shows the formation of single crystals of linear UHMWPE, identifying the fold surface and crystal thickness and suggesting a low entangled state. The topological differences with the commercial entangled sample are identified by chain diffusion from the noncrystalline to crystalline region via solid-state NMR, following melting kinetics via DSC, and transformation of the nonequilibrium melt into the equilibrium state via rheology. Thus, the obtained disentangled crystals can be compressed in the solid state, without melting, to an extent that the macroscopic forces can be transferred to the molecular level. This allows the desired chain orientation for securing the ultimate tensile modulus (>200 N/tex) and tensile strength (>4.0 N/tex) in the synthesized low entangled linear polyethylene having a weight average molar mass exceeding a million grams per mole. These mechanical properties are equivalent to those perceived using a homogeneous catalytic system and are the first of their kind reported in a polymer synthesized using a heterogeneous catalytic system.

Current Outlooks on Machine Learning Methods for the Development of Industrial Homogeneous Catalytic Systems

Abstract: This brief perspective outlines the pivotal role of Machine Learning methods in the green, digital transition of industrial chemistry. The focus on homogenous catalysis highlights the recent methodologies in the development of industrial processes, including the design of new catalysts and the enhancement of sustainable reaction conditions to lower production costs. We report several examples of Machine Learning assisted methodologies through recent Data Science trends on innovation of industrial homogeneous organocatalytic systems. We also stress the current benefits, drawbacks, and limitations towards the mass implementation of these Data Science methodologies.

Electrochemically CO2 conversion using homogeneous and nanostructured heterogeneous Ru (II) electrocatalysts

The reduction of carbon dioxide to desirable products is an urgent goal in favour of the environment, the energy-cycle and mankind. We report the electrochemical reduction of CO2 to carbon monoxide by means of the homogeneous electrocatalyst (1), [Ru(bpy)2(L1)](ClO4)2, and the heterogeneous one (2), [Ru(bpy)2L1](ClO4)2@SiO2-NH2@Fe3O4) (meaning 1 fixed onto functionalized nanoparticles). The catalysts have been synthesized and characterized using different spectroscopies (IR, UV–vis, EDAX, SEM and PXRD(. The crystal structure of 1, determined by X-ray diffraction, revealed a distorted octahedral coordination of the Ru (II) center. In 1 the electrocatalytic activity of the complex was investigated for the CO2 reduction under various reaction conditions; this complex is stable and active for the CO2 reduction to CO in 0.5 M of a TBHP acetonitrile electrolyte. Under heterogeneous condition, both 1 and 2 show small electrocatalytic activity for CO2 reduction and remarkable electrocatalytic activity for H2 evolution in 0.5 M KHCO3 aqueous electrolyte, which can be attributed to the HCO3¯ mediated hydrogen evolution reaction (HER) process. It is expected that this could introduce a new type of the electrocatalysts for syngas production from CO2 and H2O in both homogeneous and heterogeneous catalytic systems.

Photoactive Copper Complexes: Properties and Applications.

Photocatalyzed and photosensitized chemical processes have seen growing interest recently and have become among the most active areas of chemical research, notably due to their applications in fields such as medicine, chemical synthesis, material science or environmental chemistry. Among all homogeneous catalytic systems reported to date, photoactive copper(I) complexes have been shown to be especially attractive, not only as alternative to noble metal complexes, and have been extensively studied and utilized recently. They are at the core of this review article which is divided into two main sections. The first one focuses on an exhaustive and comprehensive overview of the structural, photophysical and electrochemical properties of mononuclear copper(I) complexes, typical examples highlighting the most critical structural parameters and their impact on the properties being presented to enlighten future design of photoactive copper(I) complexes. The second section is devoted to their main areas of application (photoredox catalysis of organic reactions and polymerization, hydrogen production, photoreduction of carbon dioxide and dye-sensitized solar cells), illustrating their progression from early systems to the current state-of-the-art and showcasing how some limitations of photoactive copper(I) complexes can be overcome with their high versatility.

Acceptorless Dehydrogenation of Aliphatics, Amines, and Alcohols with Homogeneous Catalytic Systems

AbstractThe dehydrogenation of saturated substrates is fundamentally essential for producing value-added unsaturated organic molecules both in academia and industry. In recent years, homogeneously catalyzed acceptorless C–C, C–N, and C–O bond desaturations have attracted increasing attention due to high atom economy, environmentally benign nature, and wide availability of the starting materials. This short review discusses the acceptorless dehydrogenation of aliphatics, alcohols, and amines by homogeneous catalytic systems based on two categories of reaction mechanisms: thermal transition-metal-catalyzed two-electron pathway and photoredox catalyzed or electrochemically driven one-electron pathway.1 Introduction2 Catalytic Acceptorless Dehydrogenation of Aliphatics3 Catalytic Acceptorless Dehydrogenation of Amines4 Catalytic Acceptorless Dehydrogenation of Alcohols5 Conclusion

In Situ X-ray Absorption Spectroscopy Cells for High Pressure Homogeneous Catalysis

We have designed, built, and tested two cells for in situ and, potentially, operando X-ray absorption spectroscopy experiments in transmission and fluorescence modes. The cells were developed for high-pressure and high-temperature conditions to study the catalytic processes under relevant industrial conditions. Operation of the cells was tested for Ru and Rh-based homogeneous and heterogeneous catalytic systems. Using synchrotron-based in situ X-ray absorption spectroscopy we tracked the evolution of active metal species during catalytic reactions. Our setup proved that it was capable to investigate liquid-state homogeneous and heterogenous systems under elevated temperatures, high pressures of reactive gasses, and in the presence of corrosive reagents.

Homogeneous Hydrogenation of CO2 and CO to Methanol: The Renaissance of Low-Temperature Catalysis in the Context of the Methanol Economy.

The traditional economy based on carbon-intensive fuels and materials has led to an exponential rise in anthropogenic CO2 emissions. Outpacing the natural carbon cycle, atmospheric CO2 levels increased by 50 % since the pre-industrial age and can be directly linked to global warming. Being at the core of the proposed methanol economy pioneered by the late George A. Olah, the chemical recycling of CO2 to produce methanol, a green fuel and feedstock, is a prime channel to achieve carbon neutrality. In this direction, homogeneous catalytic systems have lately been a major focus for methanol synthesis from CO2 , CO and their derivatives as potential low-temperature alternatives to the commercial processes. This Review provides an account of this rapidly growing field over the past decade, since its resurgence in 2011. Based on the critical assessment of the progress thus far, the present key challenges in this field have been highlighted and potential directions have been suggested for practically viable applications.

Homogeneous Hydrogenation of CO2 and CO to Methanol: The Renaissance of Low‐Temperature Catalysis in the Context of the Methanol Economy

AbstractThe traditional economy based on carbon‐intensive fuels and materials has led to an exponential rise in anthropogenic CO2 emissions. Outpacing the natural carbon cycle, atmospheric CO2 levels increased by 50 % since the pre‐industrial age and can be directly linked to global warming. Being at the core of the proposed methanol economy pioneered by the late George A. Olah, the chemical recycling of CO2 to produce methanol, a green fuel and feedstock, is a prime channel to achieve carbon neutrality. In this direction, homogeneous catalytic systems have lately been a major focus for methanol synthesis from CO2, CO and their derivatives as potential low‐temperature alternatives to the commercial processes. This Review provides an account of this rapidly growing field over the past decade, since its resurgence in 2011. Based on the critical assessment of the progress thus far, the present key challenges in this field have been highlighted and potential directions have been suggested for practically viable applications.

Molecular Organosulphur, Organoselenium and Organotellurium Complexes as Homogeneous Transition Metal Catalytic Systems for Suzuki Coupling

AbstractDuring last two decades, researchers have employed organochalcogen compounds as ligands for the development of pre‐formed chalcogen ligated molecular complexes. During 2013–2020, various chalcogen containing homogenous catalytic systems for Suzuki Miyaura cross‐coupling reaction have been synthesized. The review provides insights into the synthetic methodologies for the preparation of organochalcogen ligands and their transition metal complexes. Another central aspect discussed is the application of such catalytic systems in Suzuki Miyaura coupling. Rationalization about the effect of temperature, substrate scope, organoborane derivatives and aryl halides employed has been elaborated. Effect of binding mode, ligand framework, chalcogen donor atom, metal and many other aspects that influence the catalytic potential of various systems have also been covered. Various other aspects such as green catalysis, use of non‐conventional energy sources have also been analyzed.

Doping Sb into CuFe2O4 improved the catalytic performance in the electrochemically enhanced homogeneous peroxymonosulfate-heterogeneous catalytic system for the degradation of ciprofloxacin

In this study, the electrochemically enhanced homogeneous-heterogeneous catalytic system (EC/Sb-CuFe2O4/PMS and EC/Sn-CuFe2O4/PMS) was constructed by placing the heterogeneous CuFe2O4-based catalyst in parallel between the anode and the cathode, which was applied to activate PMS to remove ciprofloxacin (CIP). Sb and Sn were doped into CuFe2O4 nanosheets to improve its intrinsic catalytic performance. Under the optimal conditions (3.5 mM PMS, the catalyst area of 4 × 5 cm2, natural pH and the current density of 15 mA/cm2), 90.3 % of CIP was removed by the proposed EC/Sb-CuFe2O4/PMS system, which was much higher than that of the EC/CuFe2O4/PMS (71.56 %) and EC/Sn-CuFe2O4/PMS (77.71 %) systems. The enhanced degradation performance of EC/Sb-CuFe2O4/PMS system was mainly due to the increased species and content of low-valence metal ions (beneficial to the activation reaction of PMS) and the rougher surface for the sufficient contact between the Sb-CuFe2O4 heterogeneous catalyst and the homogeneous PMS, which in return promoted the activation of PMS and generated more ·OH and SO4·- for the degradation of CIP. The generated intermediates in the degradation process were analyzed and the possible degradation pathways were proposed. The developed EC/Sb-CuFe2O4/PMS system was a potential candidate for the degradation of CIP in the environment. In addition, improving the catalytic performance of heterogeneous spinel catalysts by moderate doping also provided new opportunities to develop more efficient catalytic materials.

Use of Porphyrin Containing Porous Materials in Heterogeneous Catalyst

Due to their potential applications in catalysis, separation, gas storage, drug delivery, and biosensing, porous materials (PMs) such as porous organic polymers (POPs), polymers with intrinsic microporosity (PIMs), porous coordination polymers (PCPs), and metal–organic frameworks (MOFs), have received much attention. Various building blocks have been prepared and demonstrated various functional materials. Among the various organic building blocks, porphyrin has become one of the most important building blocks for the construction of such materials witnessed by a wide range of molecular architectures using porphyrin derivatives with various applications. Mn(III)- and Fe(III)-containing metalloporphyrins are often used to fabricate various functional molecular architectures and to mimic the extraordinary behavior of enzymes in both homogeneous and heterogeneous catalytic systems. In the case of homogeneous catalysis, Mn(III)- and Fe(III)-containing metalloporphyrins have frequent trouble with fast catalytic degradation because of µ-oxo dimer formation or ligand oxidation. To avoid the catalyst degradation, the immobilization and/or site-isolation of homogeneous catalysts using supporters such as polymers, membranes, and MOFs, are widely used strategy. In addition, they are often used to modify the surface of porous silica materials such as SBA-15, MCM-41 and MCM-48, because these porous silica materials exhibit narrow pore size distributions, high thermal stability and easy accessibility.In this presentation, we like to show the use of metalloporphyrins in various porous materials and their use as heterogeneous catalysts.References D. Y. Shin, J. H. Yoon, S. H. Kim, H. Baik, S. J. Lee,* "Immobilization of Porphyrinic Mn(III) Catalyst on a New Class of Silica Support Comprising Three-Dimensionally Interconnected Network with Two Different Sizes of Pores", Catal. Sci. Technol. 2018, 8, 6306-6310.J. Yi, H. Y. Jeong, D. Y. Shin, C. Kim, S. J. Lee,* "Mn(III)-Porphyrin Containing Heterogeneous Catalyst based on Microporous Polymeric Constituents as a New Class of Catalyst Support", ChemCatChem 2018, 10, 3974-3977.J. Yoon, H. M. Choi, S. J. Lee,* "Cu(II)Cl2 containing bispyridine-based porous organic polymer support prepared via alkyne–azide cycloaddition as a heterogeneous catalyst for oxidation of various olefins", New J. Chem. 2020, 44, 9149-9152.H. M. Choi, Y. J. Kim, E. T. Choi, S. J. Lee,* "Selective Photocatalytic Oxidative Detoxification of a Chemical Warfare Agent Simulant by Porphyrin-Containing Polymers of Intrinsic Microporocity." ACS Appl. Polym. Mater.2021, submitted .

Acceleration of Baylis-Hillman Reaction using Ionic Liquid Supported Organocatalyst

Background: Baylis-Hillman reaction requires cheap starting materials, easy reaction protocol, and possibility to create the chiral center in the reaction product has increased the synthetic efficacy of this reaction which also suffers from high catalyst loading, low reaction rate, and poor yield. Objective: The extensive use of various functional or non-functional ionic liquids (ILs) with organocatalyst acts not only as reaction medium but also as a support to anchor the catalysts to increase the reaction rate of various organic transformations. Methods: In this manuscript, we have demonstrated the synthesis of quinuclidine-supported trimethylamine-based functionalized ionic liquid as a catalyst for the Baylis-Hillman reaction. Results: We obtained the Baylis-Hillman adducts in good, isolated yield along with low catalyst loading, short reaction time, wide substrate scope, easy product, and catalyst recycling. N- ((E,3S,4R)-5-benzylidene-tetrahydro-4-hydroxy-6-oxo-2H-pyran-3-yl) palmitamide was also successfully synthesized using CATALYST-3 promoted Baylis-Hillman reaction. Conclusion: We successfully isolated the 25 types of Baylis-Hillman adducts using three different quinuclidine-supported ammonium-based ionic liquids such as Et3AmQ][BF4] (CATALYST-1), [Et3AmQ][PF6] (CATALYST-2), and [TMAAmEQ][NTf2](CATALYST-3) as new and efficient catalysts. Generally, all the reactions demonstrated higher activity and gave good to high yield in competition with various previously reported homogenous and heterogeneous catalytic systems. Easy catalyst and product recovery followed by 6 times of catalysts recycling were the added advantages of the prosed catalytic system. Tedious and highly active N-((E,3S,4R)-5-benzylidene-tetrahydro- 4-hydroxy-6-oxo-2H-pyran-3-yl) palmitamide derivative was also synthesized using CATALYST- 3 followed by Baylis-Hillman reaction.

Recent Achievements in the Synthesis of Cyclic Carbonates from Olefins and CO2: The Rational Design of the Homogeneous and Heterogeneous Catalytic System

With the consumption of fossil fuels, the level of CO2 in the atmosphere is growing rapidly, which leads to global warming. Hence, the chemical conversion of CO2 into high value-added products is one of the most important approaches to reducing CO2 emissions. Due to being simple, inexpensive and environmentally friendly, the direct synthesis of cyclic carbonates from olefins and CO2 is a promising project for industrial application. In this review, we discuss the design of the homogeneous and heterogeneous catalytic system for the synthesis of cyclic carbonates from the reaction of olefins and CO2. Usually, the catalyst contains the epoxidation active site and the cycloaddition active site, which could achieve the oxidation of oleifins and the CO2-insert, respectively. This review will provide a comprehensive overview of the direct synthesis of cyclic carbonates from olefins and CO2 catalyzed by homogeneous and heterogeneous catalysts. The focus mainly lies on the rational fabrication of multifunctional catalysts, and provides a new perspective for the design of catalysts.