Catalysis Of Organic Reactions Research Articles

Recent advances in homogeneous photocatalytic carboxylation incorporated with CO<sub>2</sub>

<p indent="0mm">Carbon dioxide (CO₂) has the advantages of low price, non-toxic, abundant and renewable. As CO₂ is an indispensable part of natural photosynthesis, it seems feasible to achieve artificial CO₂ fixation with the aid of light. For light-driven utilization of CO₂, two major categories can be diversified: (1) Photoreduction of CO₂ into other C1 resources, such as carbon monoxide, methanol, formic acid, and methane; (2) photocarboxylation, which is a green and sustainable method of fixing CO₂ into organic molecules. Therefore, taking CO₂ as a C1 synthon to participate in the reaction is an effective means to utilize it. Carrying out carboxylation reaction with CO₂ as raw material to produce acrylic acid, benzoic acid or other high value-added carboxylic acid derivatives has been a very important research significance. The carboxylation reactions using CO₂ usually include: (1) The use of strong nucleophiles such as Grignard reagents; (2) the use of stoichiometric metal reducing agents; (3) high temperature, high pressure and other conditions to activate the thermodynamic and dynamic stable CO₂. In the past decade, the homogeneous photocatalytic reaction has made a great progress. Researchers found photocatalytic organic reactions have many advantages, such as mild reaction conditions, high selectivity, and environmental protection. Compared to conventional thermal reaction system with CO₂ in the carboxylation reaction, the carboxylation reaction in photocatalysis has the following advantages: (1) Avoid the utilization of unstable strong reductant; (2) most of the reaction under mild conditions are performed; (3) during the reaction and post-processing to reduce the environmental impact. This article mainly introduces and summarizes the homogeneous carboxylation reactions involving photocatalytic CO₂ in recent years. At the same time, the study of mechanism is also an important part in the homogeneous photocatalytic reaction, especially in the field of the carboxylation reactions. The current photocatalytic carboxylation reaction can be roughly divided into three categories: (1) The electron transfer process occurs between the substrate and the photocatalyst, and the nucleophilic attack on the CO₂ molecule occurs after the formation of the corresponding anion intermediate to achieve carboxylation; (2) single electron transfer (SET) occurs between the CO₂ molecule and the photocatalyst, forming a CO₂ radical anion and then reaction with the substrates; (3) with assistant of the transition metal to form complex with the substrate and/or CO₂, a series of photocatalytic electron transfer processes and ligand transfer reactions to achieve the carboxylation. In addition, there is a carboxylation reaction realized by a synergistic [4+2] mechanism. Considering the importance of the study on the reaction mechanism in organic catalytic reactions, this article will focus on the employ the different types of intermediates generated in the reaction to achieve the homogeneous photocatalytic carboxylation of various substrates with CO₂, which include four types reaction mechanisms such as anionic intermediates, CO₂ radical anions, transition metal participation, and synergistic processes.

Noble metal loaded ZnCr-LDH based hybrid material for Suzuki coupling reactions: A comparison study on heterogeneous catalysis with photo catalysis

Here, we particularly address the utilization of noble metal loaded LDH based organic–inorganic hybrid materials as heterogeneous catalysts as well as a photo catalyst for sustainable and cleaner organic transformation reactions in fine chemical industries. The highly efficient noble metal nano particles (NPs) like gold (Au) and palladium (Pd) can effectively catalysed the thermal reaction as well as photo catalytic organic reactions. Among the new generation photo catalyst, AuPd alloy loaded LDH (LDH@AuPd) was very much promising material for Suzuki coupling reaction. The Suzuki coupling product (biphenyl) yield was found to be around 98% over the LDH@AuPd composite in photo reaction (time = 2 h at room temp), where as biphenyl yield was around 96% over LDH@Pd NCs in case of thermal reaction (time = 10 h at 80°C). The combined effects of the bimetallic AuPd alloy-based nano composite provide a novel platform for excellent photo catalytic activity towards the Suzuki coupling reactions. So, major consideration should be given to photo catalysts by means of the prospective to be stimulated by the visible light, so as to get cost effectiveness of the photo catalytic organic synthesis. This functionalised photo catalysts can be reused multiple times and recovered merely without considerable loss in catalytic activity and selectivity, which is an enhanced option for practical purposes.

Direct and quantitative monitoring of catalytic organic reactions under heterogeneous conditions using direct analysis in real time mass spectrometry.

This new method overcomes problems of conventional analytical methodologies such as light scattering and sampling reproducibility issues. We used this method for mechanistic studies of catalytic reactions under heterogeneous conditions. Direct-type hydroxymethylation reactions and Mukaiyama-type hydroxymethylation reactions both catalyzed by a scandium–bipyridine ligand complex under micellar conditions were employed as examples of heterogeneous reactions. For direct-type hydroxymethylation reactions, initial reaction rate assays revealed first-order dependency on both substrate and catalyst. On the other hand, Mukaiyama-type hydroxymethylation reactions showed first-order rate dependency on substrate, zero-order on catalyst and saturation kinetics on formaldehyde.

Ion-imprinted mesoporous silica/magnetic graphene oxide composites functionalized with Schiff-base for selective Cu(II) capture and simultaneously being transformed as a robust heterogeneous catalyst

Ascribing to the risk on public health and environment, as well as the extensive applications of copper, the highly selective capture and effective utilization of the recovered Cu(II) ion by using a multifunctional material are of significant practical interest. However, there remains an arduous challenge to the fulfillment of such tasks. In this study, using the mesoporous silica/magnetic graphene oxide composites (MS/MGO) as the support, 2-((2-(3-(trimethoxysilyl)propylamino)ethylimino)methyl)phenol (TPEMP) bearing Schiff-base as the functional monomer, surface Cu(II) ion-imprinted polymers (Cu(II)-IIPs) were fabricated and applied for the selective capture Cu(II) ion from aqueous media. Additionally, the reuse of the spent Cu(II) loaded adsorbent (SMS/MGO-Cu) to the catalytic application was also explored. The obtained samples were characterized by various techniques. The uptake of Cu(II) by Cu(II)-IIP-2 was tested through the study of pH effect, sorption isotherms and uptake kinetics, selective sorption, adsorbent regeneration. The results indicated the Cu(II)-IIP-2 had high selectivity and faster kinetic over reported adsorbents, with an equilibrium adsorption capacity of 195.3 mg/g at 298 k within 30 min. Sorption isotherms were well described by the Langmuir model, while the uptake kinetics was fitted by the pseudo-second order rate equation. In addition, the Cu(II)-IIP-2 could be recycled six times without any significant loss in adsorption capacity. Importantly, the best catalysis efficiency of SMS/MGO-Cu for the synthesis of 1-methyl-4-(p-tolyloxy)benzene was 95%. These results indicate the Cu(II)-IIP-2 can not only be applied to effectively remove Cu(II) ion from aqueous media, but also be used in heterogeneous catalytic organic synthesis reactions after sorption.

η5-Cp*B-Mes]+: A Masked Potent Boron Lewis Acid

The chemistry of the boron cation has been revitalized in the past decade due to its newfound application in stoichiometric and catalytic organic reactions. To extend the frontier of boron cation c...

Combination of Experimental and Computational Approaches: Recent Developments in Catalytic Organic and Bioorganic Reactions

Combination of Experimental and Computational Approaches: Recent Developments in Catalytic Organic and Bioorganic Reactions

Rare-Earth Y(OTf)3 Catalyzed Coupling Reaction of Ethers with Azaarenes.

Rare-earth catalysis has become a hot topic in the field of catalytic organic reaction. Chain ethers mostly have lower reactivity and lower boiling points which limited their reaction scope. Herein, we found a rare-earth Y(OTf)3 can catalyze the coupling reaction of ethers especially chain ethers and thioethers with azaarenes. This protocol features simple operations, a broad substrate scope (31 examples), moderate to good yields (up to 85%), and atom economy.

Catalysis of Organic Reactions through Halogen Bonding

Halogen bonding, the noncovalent interaction based on electrophilic halogen substituents, features very interesting properties, as illustrated by numerous applications continuously emerging in rece...

Metal—Organic Frameworks in Asymmetric Catalysis: Recent Advances

The review summarizes recent advances in the use of homochiral metal—organic frameworks (MOFs) in asymmetric catalysis of organic reactions.

Atomically Precise Noble Metal Nanoclusters as Efficient Catalysts: A Bridge between Structure and Properties.

Improving the knowledge of the relationship between structure and properties is fundamental in catalysis. Recently, researchers have developed a variety of well-controlled methods to synthesize atomically precise metal nanoclusters (NCs). NCs have shown high catalytic activity and unique selectivity in many catalytic reactions, which are related to their ultrasmall size, abundant unsaturated active sites, and unique electronic structure different from that of traditional nanoparticles (NPs). More importantly, because of their definite structure and monodispersity, they are used as model catalysts to reveal the correlation between catalyst performance and structure at the atomic scale. Therefore, this review aims to summarize the recent progress on NCs in catalysis and provide potential theoretical guidance for the rational design of high-performance catalysts. First a brief summary of the synthetic strategies and characterization methods of NCs is provided. Then the primary focus of this review-the model catalyst role of NCs in catalysis-is illustrated from theoretical and experimental perspectives, particularly in electrocatalysis, photocatalysis, photoelectric conversion, and catalysis of organic reactions. Finally, the main challenges and opportunities are examined for a deep understanding of the key catalytic steps with the goal of expanding the catalytic application range of NCs.

Stereochemical features of low-coordinate organophosphorus compounds

Various kinds of sterically protected low-coordinate phosphorus compounds with Mes* (2,4,6-tri-tert-butylphenyl) group such as diphosphenes, 1-phosphaethenes, 1-phosphaallenes, 1,3-diphosphaallenes, and 3,4-diphosphinidenecyclobutenes are discussed in terms of stereochemistry including E/Z photo-isomerization around the P = P or P = C bond and R/S identification of rotational isomers around the crowded P–C bonds. (π-Allyl)palladium complexes ligated with 3,4-diphosphinidenecyclobutenes are useful in catalytic organic reactions such as the Tsuji-Trost reaction and the mechanism is proposed to interpret products.

Phosphorus corrole complexes: from property tuning to applications in photocatalysis and triplet-triplet annihilation upconversion.

Efficient triplet photosensitizers are important for fundamental photochemical studies and applications such as triplet-triplet annihilation upconversion (TTA UC), photoredox catalytic organic reactions and photovoltaics. We now report a series of phosphorus corrole compounds as efficient visible light-harvesting metal-free triplet photosensitizers. While the heavy-atom-free phosphorus corroles show absorption in the visible spectral region (centered at 573 nm) and have a decent triplet state quantum yield (Φ Δ = 49%), iodo-substitution on the corrole core induces red-shifted absorption (589 nm) and improves intersystem crossing significantly (Φ Δ = 67%). Nanosecond transient absorption spectra confirm triplet state formation upon photoexcitation (τ T = 312 μs) and the iodinated derivatives also display near IR phosphorescence in fluid solution at room temperature (λ em = 796 nm, τ p = 412 μs). Both singlet oxygen (1O2) and superoxide radical anions (O2 -˙) may be produced with the phosphorus corroles, which are competent photocatalysts for the oxidative coupling of benzylamine (the Aza Henry reaction). Very efficient TTA UC was observed with the phosphorus corroles as triplet photosensitizers and perylene as the triplet acceptor, with upconversion quantum yields of up to Φ UC = 38.9% (a factor of 2 was used in the equation) and a very large anti-Stokes effect of 0.5 eV.

PdAu alloy nanoparticles supported on nitrogen-doped carbon black as highly active catalysts for Ullmann coupling and nitrophenol hydrogenation reactions.

Noble metal-based catalysts have been proven to be active for catalytic organic reactions. The selectivity and conversion can be improved by integration with proper carrier materials, and further modulated by tuning the composition as well as the electronic structure of the active noble metals. Compared with unsupported monometallic catalysts, the synergistic interactions between neighboring metals and the combined effects between the carrier materials and the active components often give rise to positive influences on the enhancement of the catalytic efficiency and selectivity. In this work, we report a facile process for the fabrication of nitrogen-doped carbon black (NCB) supported PdAu bimetallic nanoparticles (NPs) with a uniform dispersion and narrow size distribution. The PdAu/NCB catalyst with a Pd/Au mole ratio of 1/1 shows the highest activity towards both Ullmann coupling reactions of aryl halides and the hydrogenation reaction of nitrophenols. Moreover, this bimetallic catalyst also exhibits a superior recycling durability to that of monometallic Pd/NCB and Au/NCB catalysts. The enhanced catalytic performance of the bimetallic catalyst is mainly due to the large BET specific surface area (125.45 m2 g−1) and the synergy between the individual components of the catalyst.

Superwettability-Based Interfacial Chemical Reactions.

Superwetting interfaces arising from the cooperation of surface energy and multiscale micro/nanostructures are extensively studied in biological systems. Fundamental understandings gained from biological interfaces boost the control of wettability under different dimensionalities, such as 2D surfaces, 1D fibers and channels, and 3D architectures, thus permitting manipulation of the transport physics of liquids, gases, and ions, which profoundly impacts chemical reactions and material fabrication. In this context, the progress of new chemistry based on superwetting interfaces is highlighted, beginning with mass transport dynamics, including liquid, gas, and ion transport. In the following sections, the impacts of the superwettability-mediated transport dynamics on chemical reactions and material fabrication is discussed. Superwettability science has greatly enhanced the efficiency of chemical reactions, including photocatalytic, bioelectronic, electrochemical, and organic catalytic reactions, by realizing efficient mass transport. For material fabrication, superwetting interfaces are pivotal in the manipulation of the transport and microfluidic dynamics of liquids on solid surfaces, leading to the spatially regulated growth of low-dimensional single-crystalline arrays and high-quality polymer films. Finally, a perspective on future directions is presented.

Low-coordinate organophosphorus compounds: some stereochemical considerations

Abstract Utilizing 2,4,6-tri-tert-butylphenyl as a sterically demanding group (abbreviated as Mes*), we have been successful in isolation, characterization, physical and chemical property investigation of low-coordinate organophosphorus compounds such as those carrying P=P and P=C bonds. Diphosphene, 1-phosphaethene, 1,3-diphosphaallene, 1-phosphaallene, and 3,4-diphosphinidenecyclobutenes are discussed in terms of stereochemistry including E/Z isomerization around P=P or P=C bond and R/S resolution of rotational isomers around crowded P–C bonds with chiral HPLC column. (π-Allyl)palladium complexes ligated with 3,4-diphosphinidenecyclobutene are useful in such catalytic organic reactions as the Tsuji-Trost reaction by which from a chiral s-alcohol, the corresponding chiral amine is obtained with retention of chirality suggesting double inversion process.

Novel reactivation allows effective reuse of Nafion® super-acid nano-catalyst

An alternative clean regeneration method to calcination on special grade resins, i.e. Nafion, is introduced. The reactivation strategy makes use of advanced oxidation processes (Fenton and non-Fenton) to remove the organic deposits generated from sequential catalytic cycles. Hot water treatment was considered as a control case to evaluate the extraction capacity of water itself at the oxidative conditions. Advanced oxidation processes were effective in reactivating the Nafion SAC-13 resin, which also rendered a cleaner and more sustainable reactivation process. Beta zeolite was studied as model fouled system prior to the Nafion SAC-13. Even though zeolites are considered to be thermally stable, this approach can be used when a full preservation of the acid sites is required. As far as resin Nafion SAC-13 is concerned, organic species deposition was found to be responsible of a selective poisoning of the sulfonic groups in Nafion, with a consequent drop in catalytic activity of the octanoic acid esterification with methanol. The Nafion resin was reactivated either with H2O2 or with Fenton chemistry; the resin remained stable under these oxidative conditions, which is the benefit of the presented non­thermal methodologies as compared to calcination. The optimal method showed full recovery of the initial activity and 90% of the final conversion. This methodology seems attractive for a whole-range of organic catalytic reactions, including those related to biomass valorization, that require the use of highly acidic catalysts, such as acidic resins, in liquid phase reactions.

Recent advances on metal-free graphene-based catalysts for the production of industrial chemicals

With the development of carbon catalysts, graphene-based metal-free catalysts have drawn increasing attention in both scientific research and in industrial chemical production processes. In recent years, the catalytic activities of metal-free catalysts have significantly improved and they have become promising alternatives to traditional metal-based catalysts. The use of metal-free catalysts greatly improves the sustainability of chemical processes. In view of this, the recent progress in the preparation of graphene-based metal-free catalysts along with their applications in catalytic oxidation, reduction and coupling reactions are summarized in this review. The future trends and challenges for the design of graphenebased materials for industrial organic catalytic reactions with good stabilities and high catalytic performance are also discussed.

Advances in Development of C–H Activation/Functionalization Using a Catalytic Directing Group

AbstractThe transition metal catalyzed direct site‐selective carbon –hydrogen functionalization is ubiquitous in organic synthesis and has reached an impressive level of sophistication and efficiency emerging as a powerful synthetic strategy for C–C bond and C–X bond formation to access various useful arylated organic molecules. For the past two decades, directing group strategy has been used for selective activation and functionalization of certain inert C–H bonds. Despite the enormous development in this field, still, the majority of systems require two redundant steps, i. e. installation and removal of DGs. To overcome these limitations, recently, traceless and multitasking groups were invented as a partial solution to DG release however installation still remains unsolved. Ideally, use of the catalytic directing group, which can be reversibly linked to the substrate and can serve as an efficient directing role would circumvent this problem and is considered as one of the most efficient and powerful strategies for the non‐activated C–H functionalization (C(sp2)–H or C(sp3)–H). In this review, we describe the enormous advances in this field for direct selective C–H functionalization without involving additional steps, i. e. installation and removal of directing groups and also discuss less explored but significant non‐covalent interactions such as hydrogen bonding or ion pairing, which helps to control the selectivity of a substrate in a catalytic organic reaction.

WO3 nanospheres with improved catalytic activity for visible light induced cross dehydrogenative coupling reactions

Three tungsten oxides (WO3-W1 to WO3-W3) with different morphologies were prepared and characterized by XRD, SEM, TEM and HR-TEM measurements. The as-synthesized tungsten oxides were screened as photocatalysts for visible-light-driven cross dehydrogenative coupling (CDC) reactions along with commercially available WO3-W4. Preliminary studies showed that WO3-W1 with hollow sphere morphology efficiently photocatalyzed oxidative CH functionalization as compared to other tested samples, by using molecular oxygen as a benign oxidant. The superior photocatalytic performance of WO3-W1 can be attributed to its larger surface area and pore structure which was supported by nitrogen adsorption-desorption measurements. Further, this protocol was used to synthesize α-functionalized tertiary amines in good to excellent yields by irradiating a mixture of WO3-W1, tertiary amine, and nucleophiles (nitromethane or ketones) to visible light under aerobic conditions. Moreover, WO3-W1 can be recycled and reused with no obvious change in catalytic activity, indicating that this is an environmentally friendly and economical protocol and also underlines the robustness of the catalysts in light mediated cross dehydrogenative coupling reactions. It is hoped that our results could offer useful information for designing of new heterogeneous semiconductors for photoredox catalytic organic reactions.

Clay Mineral Catalysis of Organic Reactions

The book provides insight into the working of clays and clay minerals in speeding up a variety of organic reactions. Clay minerals are known to have a large propensity for taking up organic molecules and can catalyse numerous organic reactions due to fine particle size, extensive surface area, layer structure, and peculiar charge characteristics. They can be used as heterogeneous catalysts and catalyst carriers of organic reactions because they are non-corrosive, easy to separate from the reaction mixture, and reusable. Clays and clay minerals have an advantage over other solid acids as they are abundant, inexpensive, and non-polluting.