Polyisobutylene supports—a non-polar hydrocarbon analog of PEG supports

Synthetic routes to terminally functionalized polyisobutylene oligomers useful as supports in synthesis and catalysis are discussed and described. Such hydrocarbon polymers serve as highly soluble non-polar analogs of well known poly(ethylene glycol) supports for synthesis and catalysis with the difference that they are separated after a reaction by an extraction with alkane solvent.     

Shining light on photoredox catalysis: theory and synthetic applications

Photoredox catalysis is emerging as a powerful tool in synthetic organic chemistry. The aim of this synopsis is to provide an overview of the photoelectronic properties of photoredox catalysts as they are applied to organic transformations. In addition, recent synthetic applications of photoredox catalysis are presented.     

树状大分子在有机合成中的应用

近20年来树状大分子由于其特殊的结构而引起了科学家们的广泛关注;作为一类新型的高负载量载体应用于有机合成和催化是树状大分子重要的应用领域之一。本文主要介绍树状大分子和树脂固载树状大分子两类载体,重点对它们作为高负载量载体在有机合成和非均相催化反应中的应用研究进行了总结。     

树状大分子在有机合成中的应用

近20年来树状大分子由于其特殊的结构而引起了科学家们的广泛关注;作为一类新型的高负载量载体应用于有机合成和催化是树状大分子重要的应用领域之一。本文主要介绍树状大分子和树脂固载树状大分子两类载体,重点对它们作为高负载量载体在有机合成和非均相催化反应中的应用研究进行了总结。     

Theoretical investigation of the origins of catalysis of a retro-Diels-Alder reaction by antibody 10F11

The antibody 10F11 catalyzes a retro-Diels-Alder reaction that forms HNO. Deductions about the mechanism of catalysis were made by Reymond, Baumann et al. from X-ray crystal structures and from kinetic measurements for mutated antibodies. We report a study of these reactions with quantum mechanical methods and a study of the substrate and transition state binding to the active site of the antibody 10F11 using density functional theory and empirical docking methods. We have quantitated the likely contributions to catalysis of three residues identified as possible causes of catalysis: Trp H104, Phe H101, and Ser H100. Trp H104 can make a significant contribution to catalysis through dispersive interactions (pi-stacking aromatic-aromatic stabilization). On its own, Phe H101 makes only a small contribution to catalysis. When both aromatic residues are present, they act cooperatively and can make greater contributions to catalysis than expected for each residue alone. Ser H100 and the backbone NH of Phe H101 are expected to act through hydrogen bonding to speed up the reaction, but our calculations suggest that they make only a small contribution to catalysis. Reymond's studies suggest that the hydrogen-bonding network may be mediated through a water molecule in the binding site.     

A Process Theory of Enzyme Catalytic Power – the Interplay of Science and Metaphysics

Enzymes are protein catalysts of extraordinary efficiency, capable of bringing about rate enhancements of their biochemical reactions that can approach factors of 10²⁰. Theories of enzyme catalysis, which seek to explain the means by which enzymes effect catalytic transformation of the substrate molecules on which they work, have evolved over the past century from the “lock-and-key” model proposed by Emil Fischer in 1894 to models that explicitly rely on transition state theory to the most recent theories that strive to provide accounts that stress the essential role of protein dynamics. In this paper, I attempt to construct a metaphysical framework within which these new models of enzyme catalysis can be developed. This framework is constructed from key doctrines of process thought, which gives ontologic priority to becoming over being, as well as tenets of a process philosophy of chemistry, which stresses environmentally responsive molecular transformation. Enzyme catalysis can now be seen not as enzyme acting on its substrate, but rather as enzyme and substrate entering into a relation which allows them to traverse the reaction coordinate as an ontologic unity.     

The Measure of All Rings—N‐Heterocyclic Carbenes

Quantification and variation of characteristic properties of different ligand classes is an exciting and rewarding research field. N‐Heterocyclic carbenes (NHCs) are of special interest since their electron richness and structure provide a unique class of ligands and organocatalysts. Consequently, they have found widespread application as ligands in transition‐metal catalysis and organometallic chemistry, and as organocatalysts in their own right. Herein we provide an overview on physicochemical data (electronics, sterics, bond strength) of NHCs that are essential for the design, application, and mechanistic understanding of NHCs in catalysis.     

Electrochemical Exfoliation of Pillared‐Layer Metal–Organic Framework to Boost the Oxygen Evolution Reaction

Two‐dimensional (2D) materials and ultrathin nanosheets are advantageous for elevating the catalysis performance and elucidating the catalysis mechanism of heterogeneous catalysts, but they are mostly restricted to inorganic or organic materials based on covalent bonds. We report an electrochemical/chemical exfoliation strategy for synthesizing metal–organic 2D materials based on coordination bonds. A catechol functionalized ligand is used as the redox active pillar to construct a pillared‐layer framework. When the 3D pillared‐layer MOF serves as an electrocatalyst for water oxidation (pH 13), the pillar ligands can be oxidized in situ and removed. The remaining ultrathin (2 nm) nanosheets of the metal–organic layers are an efficient catalyst with overpotentials as low as 211 mV at 10 mA cm^?2 and a turnover frequency as high as 30 s^?1 at an overpotential of 300 mV.     

Sustainable Production of Chemicals via Hydrotreating of CO2 and Biomass Derived Molecules Using Heterogeneous Noble Metal Oxide Catalysts

The noble metals are widely used in heterogeneous catalysis and automobile industry. The limited natural sources and high cost of noble metals dictates improving the efficiency of modern industry. This review considers the applications of noble metal oxide as potential solutions to the sustainability issues, including biomass conversion, CO₂ capture and conversion, green fuel production, etc. Noble metal oxides with their different compositions (monometallic and bimetallic) and structures exhibit a wide range of properties in heterogeneous catalysis. Although platinum metals in an oxidized form may not be the most common choice in hydroprocesses; recently, there have been studies indicating that they were highly active and selective catalysts in hydrogenation and hydrogenolysis. This review outlines the most established noble metal oxide catalysts used in hydrogenation catalysis and shed the light on the relation of noble metal oxide species to catalyst selectivity based on state-of-the-art techniques. Finally, the perspectives on the application of noble metal oxide catalysts to produce value-added chemicals are discussed.     

Methylchlorophosphanes and Their Reaction Products

Methyldichlorophosphane and dimethylchlorophosphane can be prepared only with considerable difficulty. The ease with which they yield numerous reaction products is an indication of the pronounced reactivity of these organohalophosphanes. Possible applications of such organophosphorus compounds exist inter alia in the fields of plant protection, corrosion prevention, and flame retardants, as well as in the catalysis of gas phase reactions, for instance the desulfurization of gas mixtures.     

The golden gate to catalysis

The use of gold in homogeneous catalysis is a relatively new field of transition metal catalysis, but has already witnessed spectacular achievements. By virtue of their unique ability to activate carbon-carbon double and triple bonds as soft, carbophilic Lewis acids, gold salts are highly efficient catalysts for the formation of C-C, C-O, C-N, and C-S bonds. Moreover, they are capable of activating C-H bonds of aromatic and other substrates, opening unprecedented pathways for their functionalisation. By using chiral allenes as substrates, gold catalysts can even be applied in stereoselective target-oriented synthesis.     

Driving the Transformation to Digital Catalysis

This invited Team Profile was created by a group of scientists working on concepts for research data management in catalysis in the Department of Inorganic Chemistry at the Fritz-Haber-Institut (FHI) der Max-Planck-Gesellschaft in Berlin. They recently published an article about their views on the ongoing digital transformation in catalysis research, in which the structure and current status of catalysis data are analyzed to highlight the benefits of FAIR data. Considering the fundamental aspects of catalysis as a kinetic phenomenon, they discuss how working methods should change to achieve a deeper understanding of the physical principles governing catalysis and discover new catalysts. “Achieving Digital Catalysis: Strategies for Data Acquisition, Storage and Use”, C. P. Marshall, J. Schumann, A. Trunschke, Angew. Chem. Int. Ed. Engl. 2023, 62, e202302971 .     

Etude de la stabilisation du polychlorure de vinyle avec des molecules modeles—II: Action des phosphites et des phosphines sur la degradation du Chloro-4-hexene-2

Phosphines are inhibitors of thermal degradation of 4-chloro-2-hexene because they form strong complexes with either HCl or ZnCl₂, which cause catalysis of the dehydrochlorination. Aliphatic phosphines are more efficient than aromatic phosphines. Aliphatic phosphites also act as stabilizers; they react with HCl, and may be substituted for allylic chlorine in the presence of ZnCl₂ as catalyst; the resulting phosphonate may be destroyed by HCl if phosphite is not in excess. Aromatic phosphites do not react at 60°; they only form a complex with HCl and, in the presence of ZnCl₂, they cause an increase of the dehydrochlorination rate. This effect is due to the reverse reaction, catalysed by a complex HCl-hexadiene, being slowed down because of the competing phosphite-HCl complex.     

Der Reaktionsmechanismus der allgemeinen Säure—Basen-Katalyse der Mutarotation der Glucose, 12. Mitt.: Die Aktivierungsgrößen der durch Deuteriumionen katalysierten Glucose-Mutarotation in schwerem Wasser

The free enthalpy of activation, the enthalpy of activation and the entropy of activation of the deuterium ion catalysis of the mutarotation of α-glucose in deuterium oxide have been determined and compared with those of the deuterium oxide catalysis; furthermore they have been compared with the corresponding values of the hydrogen ion catalysis and of the water catalysis and the mechanism of activation of the studied catalysis has been elucidated.     

Palladium nanoparticles as efficient green homogeneous and heterogeneous carbon-carbon coupling precatalysts: a unifying view

Pd catalysis of C-C bond formations is briefly reviewed from the angle of nanoparticles (NPs) whether they are homogeneous or heterogeneous precatalysts and whether they are intentionally preformed or generated from a Pd derivative such as Pd(OAc)2. The most studied reaction is the Heck coupling of halogenoarenes with olefins that usually proceeds at high temperature (120-160 degrees C). Under such conditions, the PdII precursor is reduced to Pd0, forming PdNPs from which Pd atom leaching, subsequent to oxidative addition of the aryl halide onto the PdNP surface, is the source of very active molecular catalysts. Other C-C coupling reactions (Suzuki, Sonogashira, Stille, Negishi, Hiyama, Corriu-Kumada, Ullmann, and Tsuji-Trost) can also be catalyzed by species produced from preformed PdNPs. For catalysis of these reactions, leaching of active Pd atoms from the PdNPs may also provide a viable molecular mechanistic scheme. Thus, the term "PdNP catalysis of C-C coupling" used in this review refers to this function of PdNPs as precursors of catalytically active Pd species (i.e., the PdNPs are precatalysts of C-C coupling reactions).     

Photocatalytic Modification of Amino Acids,Peptides, and Proteins

In the last decade, visible-light photoredox catalysis has emerged as a powerful strategy to enable novel transformations in organic synthesis. Owing to mild reaction conditions (i.e., room temperature, use of visible light) and high functional-group tolerance, photoredox catalysis could represent an ideal strategy for chemoselective biomolecule modification. Indeed, a recent trend in photoredox catalysis is its application to the development of novel methodologies for amino acid modification. Herein, an up-to-date overview of photocatalytic methodologies for the modification of single amino acids, peptides, and proteins is provided. The advantages offered by photoredox catalysis and its suitability in the development of novel biocompatible methodologies are described. In addition, a brief consideration of the current limitations of photocatalytic approaches, as well as future challenges to be addressed, are discussed.     

Transformation of macromonomers into ring‐opening polymerization macroinitiators: A detailed initiation efficiency study

In the present study, n‐butyl acrylate macromonomer (BAMM) (M_n = 1900 g mol^?1; PDI = 1.96) has been synthesized via a high‐temperature polymerization process. Subsequently, the olefinic termini of the BAMM have been transformed into a diol via a dihydroxylation process using KMnO₄ as an oxidizing agent. The OH‐terminated macroinitiator pBA(OH)₂ has subsequently been employed for the ring‐opening polymerization (ROP) of ε‐caprolactone via various catalytic systems, that is, organo‐(1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene), metal (tin(II) 2‐ethylhexanoate), and enzymatic catalysis (Novozym® 435). The obtained pBA‐b‐pCL block copolymers and the initiation efficiency of the BAMM macroinitiator have been investigated via size exclusion chromatography (SEC), electrospray ionization–mass spectrometry (ESI‐MS) hyphenated with SEC and liquid chromatography at the critical conditions of both poly(ε‐caprolactone) (pCL) and pBA. The in vitro enzyme catalysis (eROP) approach proved to be the most efficient catalysis system due to minor transesterification side reactions during the polymerization process. However, side reactions such as transesterifications occur in each catalytic system and—while they cannot be suppressed—they can be minimized. The species generated during the eROP process include the desired block copolymer pBA‐b‐pCL as main species as well as pCL homopolymer and residual macroinitiator pBA(OH)₂. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

The ying and yang of asymmetric aminocatalysis

During the last six years the asymmetric catalysis of carbonyl transformations via iminium ion and enamine intermediates using chiral amines as organocatalysts has grown most remarkably. In this personal account an overview of this area is given. The field can be divided into two sub areas: (a) Iminium catalysis, which is typically used for cycloadditions and conjugate additions to enals and enones and (b) Enamine catalysis, which is commonly used in electrophilic alpha-substitution reactions of ketones and aldehydes. A common origin of the two catalysis principles is proposed and their recent merger in tandem sequences is discussed.     

Boron: A key functional component for designing high-performance heterogeneous catalysts

Heterogeneous catalysis is a vivid branch of traditional catalysis field, with the advantage of high efficiency and being easily separated from reactants and products after reaction, and have received widespread attentions in large-scale industrial production, especially in the field of energy utilization. Boron has been found to be a key functional component for designing high-performance heterogeneous catalysts. In this review, we cover and categorize the past and recent progress in boron-containing materials and their applications in heterogeneous catalysis particularly in energy‐related fields. The fundamental roles of boron components in the emerging heterogeneous catalysis of construction, regulation and stabilization of active phases/sites are highlighted, with the emphasis on how they regulating structural and electronic properties of host materials. We then categorize boron-containing catalysts into six kinds mainly including intermetallic boride catalysts, metal boride-derived catalysts, boron-doped catalysts, metal boride-decorated catalysts, boron-containing compounds as catalyst supports, and single-boron-site catalysts, as well as try to establish structure-catalytic activity relationship. The catalytic applications of these six boron-containing catalysts are discussed separately, focusing on the energy-related reactions such as hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO₂RR) and nitrogen reduction reaction (NRR). Finally, the opportunities and challenges related to boron-containing compounds in the field of catalysis are prospected.     

吸附胶团和吸附胶团催化

介绍了吸附胶团的结构特点、影响吸附胶团催化的一些因素和在固体表面上的固定化表面活性剂体系的催化作用。吸附胶团是表面活性剂在固-液界面形成的缔合结构,它可以是吸附单层、双层、半球形、球形等。吸附胶团和利用接枝等技术在固体表面形成的不溶性表面活性剂体系,在一定条件下,可对某些反应起催化作用,有利于提高反应产率并使反应产物分离变得容易,这将使胶团催化的实际应用成为可能。