Advanced Synthesis and Catalysis
1615-4169
1615-4150
Đức
Cơ quản chủ quản: WILEY-V C H VERLAG GMBH , Wiley-VCH Verlag
Lĩnh vực:
CatalysisOrganic Chemistry
Các bài báo tiêu biểu
Enzyme Immobilization: The Quest for Optimum Performance Abstract Immobilization is often the key to optimizing the operational performance of an enzyme in industrial processes, particularly for use in non‐aqueous media. Different methods for the immobilization of enzymes are critically reviewed. The methods are divided into three main categories, viz. (i) binding to a prefabricated support (carrier), (ii) entrapment in organic or inorganic polymer matrices, and (iii) cross‐linking of enzyme molecules. Emphasis is placed on relatively recent developments, such as the use of novel supports, e.g., mesoporous silicas, hydrogels, and smart polymers, novel entrapment methods and cross‐linked enzyme aggregates (CLEAs).
Tập 349 Số 8-9 - Trang 1289-1307 - 2007
On the Nature of the Active Species in Palladium Catalyzed Mizoroki–Heck and Suzuki–Miyaura Couplings – Homogeneous or Heterogeneous Catalysis, A Critical Review
Tập 348 Số 6 - Trang 609-679 - 2006
Potential of Different Enzyme Immobilization Strategies to Improve Enzyme Performance Abstract Enzyme biocatalysis plays a very relevant role in the development of many chemical industries, e.g., energy, food or fine chemistry. To achieve this goal, enzyme immobilization is a usual pre‐requisite as a solution to get reusable biocatalysts and thus decrease the price of this relatively expensive compound. However, a proper immobilization technique may permit far more than to get a reusable enzyme; it may be used to improve enzyme performance by improving some enzyme limitations: enzyme purity, stability (including the possibility of enzyme reactivation), activity, specificity, selectivity, or inhibitions. Among the diverse immobilization techniques, the use of pre‐existing supports to immobilize enzymes (via covalent or physical coupling) and the immobilization without supports [enzyme crosslinked aggregates (CLEAs) or crystals (CLECs)] are the most used or promising ones. This paper intends to give the advantages and disadvantages of the different existing immobilization strategies to solve the different aforementioned enzyme limitations. Moreover, the use of nanoparticles as immobilization supports is achieving an increasing importance, as the nanoparticles versatility increases and becomes more accessible to the researchers. We will also discuss here some of the advantages and drawbacks of these non porous supports compared to conventional porous supports. Although there are no universal optimal solutions for all cases, we will try to give some advice to select the optimal strategy for each particular enzyme and process, considering the enzyme properties, nature of the process and of the substrate. In some occasions the selection will be compulsory, for example due to the nature of the substrate. In other cases the optimal biocatalyst may depend on the company requirements (e.g., volumetric activity, enzyme stability, etc).
Tập 353 Số 16 - Trang 2885-2904 - 2011
Recent Applications of Palladium‐Catalyzed Coupling Reactions in the Pharmaceutical, Agrochemical, and Fine Chemical Industries Abstract Palladium‐catalyzed coupling reactions have become a central tool for the synthesis of biologically active compounds both in academia and industry. Most of these transformations make use of easily available substrates and allow for a shorter and more selective preparation of substituted arenes and heteroarenes compared to non‐catalytic pathways. Notably, molecular‐defined palladium catalysts offer high chemoselectivity and broad functional group tolerance. Considering these advantages, it is not surprising that several palladium‐catalyzed coupling reactions have been implemented in the last decade into the industrial manufacture of pharmaceuticals and fine chemicals. In this review different examples from 2001–2008 are highlighted, which have been performed at least on a kilogram scale in the chemical and pharmaceutical industries.
Tập 351 Số 18 - Trang 3027-3043 - 2009
Selective Hydrogenation for Fine Chemicals: Recent Trends and New Developments Abstract In this overview, recent trends and developments for the selective hydrogenation of multifunctional molecules are discussed and assessed from the point of view of fine chemicals synthesis. In a first part, the design and preparation of catalysts and ligands with interesting properties are summarized, particularly meant for the catalysis specialist. The following topics are described in some detail: How enantioselective homogeneous catalysts are designed and tested; new effective chiral monodentate phosphines; successful bidentate phosphines ligand families (with axially chiral biaryl‐ and ferrocenyl‐based backbones, new phospholanes and with stereogenic phosphorus); novel bidentate ligand families with P‐O and P‐N bonds; and oxazoline‐based ligands. A short overview on immobilized chiral complexes and of the toolbox of heterogeneous catalysis (bimetallic, colloidal and modified catalysts) concludes this chapter. In a second part, progress for selected catalytic transformations and generic selectivity problems is described, intended mainly for the organic chemist who has to solve specific synthetic problems. Emphasis is on the following topics: The enantioselective hydrogenation of olefins with various substitution patterns; the chemo‐ and enantioselective hydrogenation of ketones; the diastereo‐ and enantioselective hydrogenation of CN functions; the stereoselective hydrogenation of aromatic rings; chemoselectivity and hydroxylamine accumulation in the reduction of functionalized nitroarenes; chemoselectivity and new protecting groups for catalytic debenzylation; the mild hydrogenation of carboxylic acid derivatives; and the chemoselective hydrogenation of nitriles. In the last parts of the review, transfer hydrogenation and mechanistic issues are discussed, followed by a short conclusions and outlook paragraph.
Tập 345 Số 1-2 - Trang 103-151 - 2003
The Art of Meeting Palladium Specifications in Active Pharmaceutical Ingredients Produced by Pd‐Catalyzed Reactions Abstract The use of palladium‐derived catalysts in the synthesis of fine chemicals, pharmaceutical intermediates and active pharmaceutical ingredients (APIs) has become quite common in the last few decades. The number of palladium‐catalyzed synthetic reactions (both achiral and chiral) available to chemists has provided access to more complex structures in fewer steps and with less waste, due to the catalytic nature of many of the methods. An unfortunate side effect of using palladium is the potential for palladium‐containing impurities to remain in the desired compound after isolation. This is an especially significant problem for the pharmaceutical industry since there is a low limit for heavy metal impurities allowed in the drug substance. Therefore, various methods of removing palladium impurities from organic compounds of pharmaceutical interest have been developed. This review will provide a survey of the published methods but is not meant to be inclusive of all published material in this area of research.
Tập 346 Số 8 - Trang 889-900 - 2004
Recent Progress in Chiral Brønsted Acid Catalysis Abstract Hydrogen bond catalysis and Brønsted acid catalysis are rapidly growing areas in organocatalysis. A number of chiral acid catalysts has been developed recently. Recent progress in the chiral Brønsted acid catalysis has been reviewed with a focus being placed on thiourea, TADDOL, and phosphoric acids. 1 Introduction 2 Hydrogen Bond Catalysis 2.1 Monofunctional Thiourea Catalysts 2.2 Bifunctional Thiourea Catalysts 2.3 TADDOL Derivatives 2.4 BINOL Derivatives 3 Brønsted Acid Catalysis 3.1 Ammonium Salts 3.2 Phosphoric Acids 4 Conclusion
Tập 348 Số 9 - Trang 999-1010 - 2006
Chiral Amine Synthesis – Recent Developments and Trends for Enamide Reduction, Reductive Amination, and Imine Reduction Abstract The review examines the chiral amine literature from 2000–2009 (May) concerning enantioselective and diastereoselective methods for N ‐acylenamide and enamine reduction, reductive amination, and imine reduction. The reaction steps for each strategy, from ketone to primary chiral amine, are clearly defined, with best methods and yields for starting material preparation and final deprotection noted. Categories of chiral amines have been defined in Section 1 to allow the reader to quickly understand whether their specific target amine falls within a difficult to synthesize, or not, structural class. Amino acids are not considered in this work.
Tập 352 Số 5 - Trang 753-819 - 2010
Palladium‐Catalyzed CN and CO Coupling–A Practical Guide from an Industrial Vantage Point<sup>†</sup> Abstract The palladium‐catalyzed coupling of amines with aryl halides or aryl alcohol derivatives, commonly dubbed Buchwald–Hartwig amination, has matured from a synthetic laboratory procedure to a technique that is widely used in natural product synthesis as well as in other fields of academic interest. Furthermore, due to the versatility and reliability of this reaction, researchers in industrial environments have included this methodology in their toolbox as a standard procedure for the synthesis of amine derivatives. Therefore, it is not surprising that first industrial processes up to ton‐scale have been performed using this cross‐coupling reaction. The authors who are involved in the application of this reaction to industrial processes on this scale give an overview of the recent developments in this field of chemistry, also including fundamental principles, with a special focus on the industrial approach and issues to be considered relevant in scaling‐up this transition metal‐catalyzed chemistry. This review differs from the already existing excellent academic reviews by focusing on the practical problems arising during implementing the methodology in an industrial environment as well as giving practical hints to this end.
Tập 346 Số 13-15 - Trang 1599-1626 - 2004
Room Temperature Aerobic Copper–Catalysed Selective Oxidation of Primary Alcohols to Aldehydes Abstract A novel and very mild method for the oxidation of primary alcohols to aldehydes with excellent conversions has been developed. The reaction is carried out under air at room temperature and is catalysed using a [copper(II)‐(N ligand)n ] complex with TEMPO and a base as co‐catalysts. In this paper, the performance of a series of N‐containing ligands, as well as different copper(II) salt precursors in different solvents are reported. Best results are obtained in acetonitrile/water as solvent using a copper(II) catalyst generated in situ from a Cu(II) salt with weak or non‐coordinating anions and bipyridine ligands with electron‐donating substituents. A reaction mechanism is postulated which resembles that of galactose oxidase, and in which TEMPO seems to be involved as a hydrogen acceptor.
Tập 346 Số 7 - Trang 805-811 - 2004