Gold and silver assisted synthesis of five-membered oxygen and nitrogen containing heterocycles

The investigation of methods for the chemical synthesis is a growing area of interest due to increasing environmental issues. The use of catalysts in organic reactions has gained extensive interest. Metal and nonmetal catalysts provided a new improved alternative to traditional methods in modern synthetic chemistry. The aim of the present review is to focus on the applications of gold- and silver-catalytic systems for the synthesis of five-membered oxygen- and nitrogen-heterocycles.     

Seven and higher-membered oxygen heterocycles: Metal and non-metal

The investigation of methods for the chemical synthesis is a growing area of interest due to increasing environmental issues. The use of catalysts in organic reactions has gained extensive interest. Metal and nonmetal catalysts provided a new improved alternative to traditional methods in modern synthetic chemistry. The aim of present review is to focus on the applications of metals and nonmetals for the synthesis of seven and higher-membered O-heterocycles.     

Seven-membered N-heterocycles: metal and nonmetal assisted synthesis

The investigation of facial synthetic methods for chemical synthesis is a growing area of interest due to increasing environmental issues. The use of catalysts in organic reactions has gained extensive interest. Metal and nonmetal catalysts provided a new improved alternative to traditional methods in modern synthetic chemistry. The aim of the present review is to focus on the applications of metals and nonmetals for the synthesis of seven-membered N-heterocycles.     

Nickel catalysis: six membered heterocycle syntheses

Abstract

The investigation of methods for the chemical synthesis is a growing area of interest due to increasing environmental issues. The use of catalysts in organic reactions has gained extensive interest. Metal and nonmetal catalysts provide a new improved alternative to traditional methods in modern synthetic chemistry. The aim of present review is to focus on the applications of nickel for the synthesis of six membered heterocylces.     

Application of silver-promoted reactions in the synthesis of five-membered O-heterocycles

The investigation of facial protocols for chemical synthesis is a growing area of interest due to increasing environmental issues. The use of catalysts in organic reactions has gained extensive interest. Metal and nonmetal catalysts provided a new improved alternative to traditional methods in modern synthetic chemistry. The aim of the present review is to focus on the applications of silver-promoted reactions for the synthesis of oxygen containing five-membered heterocycles which have significance in organic synthesis, pharmaceuticals, agrochemicals, and among others.     

Ionic liquid: An efficient and recyclable medium for the synthesis of fused six-membered oxygen heterocycles

The investigation for replacement of organic solvents in chemical synthesis is a growing area of interest due to increasing environmental issues. The use of ionic liquid salts as solvents and catalysts in organic reactions has gained extensive interest. Ionic liquids provided a new environmentally benign and improved alternative to traditional methods in modern synthetic chemistry. The aim of present review is to focus on the applications of ionic liquids for the synthesis of fused six-membered oxygen heterocycles.     

Green synthesis of three- to five-membered O-heterocycles using ionic liquids

The investigation for replacement of organic solvents in organic synthesis is a growing area of interest due to increasing environmental issues. The use of ionic liquid salts as solvents and catalysts in organic reactions has gained extensive interest. Ionic liquids provided a new environmentally benign and improved alternative to traditional methods in modern synthetic chemistry. The aim of present review is to focus on the applications of ionic liquids for the synthesis of O-heterocycles.     

Microwave-Assisted Conversion of Carbohydrates

Catalytic conversion of carbohydrates into value-added products and platform chemicals became a trend in recent years. Microwave activation used in the processes of carbohydrate conversion coupled with the proper choice of catalysts makes it possible to enhance dramatically the efficiency and sometimes the selectivity of catalysts. This mini-review presents a brief literature survey related to state-of-the-art methods developed recently by the world research community to solve the problem of rational conversion of carbohydrates, mostly produced from natural resources and wastes (forestry and agriculture wastes) including production of hydrogen, synthesis gas, furanics, and alcohols. The focus is made on microwave technologies used for processing carbohydrates. Of particular interest is the use of heterogeneous catalysts and hybrid materials in processing carbohydrates.     

Inorganic molecular sieves: Preparation,modification and industrial application in catalytic processes

The increasing environmental concern and promotion of “green processes” are forcing the substitution of traditional acid and base homogeneous catalysts by solid ones. Among these heterogeneous catalysts, zeolites and zeotypes can be considered as real “green” catalysts, due to their benign nature from an environmental point of view. The importance of these inorganic molecular sieves within the field of heterogeneous catalysis relies not only on their microporous structure and the related shape selectivity, but also on the flexibility of their chemical composition. Modification of the zeolite framework composition results in materials with acidic, basic or redox properties, whereas multifunctional catalysts can be obtained by introducing metals by ion exchange or impregnation procedures, that can catalyze hydrogenation–dehydrogenation reactions, and the number of commercial applications of zeolite based catalysts is continuously expanding.In this review we discuss determinant issues for the development of zeolite based catalysts, going from zeolite catalyst preparation up to their industrial application. Concerning the synthesis of microporous materials we present some of the new trends moving into larger pore structures or into organic free synthesis media procedures, thanks to the incorporation of novel organic templates or alternative framework elements, and to the use of high-throughput synthesis methods. Post-synthesis zeolite modification and final catalyst conformation for industrial use are briefly discussed.In a last section we give a thorough overview on the application of zeolites in industrial processes. Some of them are well established mature technologies, such as fluid catalytic cracking, hydrocracking or aromatics alkylation. Although the number of zeolite structures commercially used as heterogeneous catalysts in these fields is limited, the development of new catalysts is a continuous challenge due to the need for processing heavier feeds or for increasing the quality of the products. The application of zeolite based catalysts in the production of chemicals and fine chemicals is an emerging field, and will greatly depend on the discovery of new or known structures by alternative, lower cost, synthesis routes, and the fine tuning of their textural properties. Finally, biomass conversion and selective catalytic reduction for conversion of NOx are two active research fields, highlighting the interest in these potential industrial applications.     

A review on catalytic reduction/degradation of organic pollution through silver-based hydrogels

Various challenging pollutants are produced in the environment by organic materials of diverse industries including leather, paint, and textile. Nowadays, it is vital to develop efficient manners regarding the fundamental issues and removing pollutants. Such pollutants can be effectively removed from the environment through heterogeneous catalysts. Recently, a huge deal of interest has been attracted by hydrogel-based metal catalysts as heterogeneous and efficient catalysts. In this regard, silver with its unique features is suitable for environmental remediation. Hence, the present review deals with summarizing the present advances in the synthesis of silver-based hydrogel catalysts, as well as their applications for environmental remediation. Some advantages have been proposed using silver-based hydrogel catalysts suggested including high catalytic ability, reusability, easy work-up, and simple synthesis.     

Immobilization of monomeric organometallic molybdenum oxo and carbonyl complexes and their application in epoxidation reactions

Various oxomolybdenum complexes are efficient and selective homogeneous catalysts in the presence of organic hydroperoxides. The increasing interest in the heterogenisation of such catalysts has led to an increased interest in finding suitable support materials for the complexes. These supports include ionic liquids, mesoporous materials and zeolites to name a few. Several methods are used to anchor the catalyst depending on the nature of the carrier material. The supported catalysts combine properties of homogeneous catalysts such as reactivity, control and selectivity with those of heterogeneous catalysts such as enhanced stability and recyclability.     

Palladium‐Catalyzed C−H Arylation of α,β‐Unsaturated Imines: Catalyst‐Controlled Synthesis of Enamine and Allylic Amine Derivatives

A unique chemo‐ and regioselective α‐ and γ‐arylation of palladium azapentadienyl intermediates is presented. Two distinct catalysts and sets of conditions successfully controlled the regioselectivity of the arylation. These methods provide the first umpolung C?H functionalization of azapentadienyl palladium intermediates and enable the divergent synthesis of allylic amine and enamine derivatives, which are of significant interest in the pharmaceutical industry.     

New emerging trends in synthetic biodegradable polymers - Polylactide: A critique

Polylactide (PLA), the biodegradable synthetic aliphatic polyester, has been studied extensively for a number of applications. With potential applications PLA represents its prospective utility in a number of growing technologies such as orthopedics, drug delivery, sutures, and scaffolds, and have further enhanced the interest of researchers in this novel area. Renewable resource generated monomers possess better mechanical properties and easy processability by conventional methods like thermoforming, injection, and blow molding with non-toxic degradation products, which have made it superior than the other conventional thermoplastics. In order to meet the different performance requirements, PLA can be synthesised by various methods using different catalysts. In this review a collection of more than 100 catalysts for the synthesis of PLA are mentioned, apart from this, efforts have been made to present an updated review on the various aspects of polylactide.     

Metal-based Heterogeneous Catalysts for One-Pot Synthesis of Secondary Anilines from Nitroarenes and Aldehydes

Recently, N-substituted anilines have been the object of increasing research interest in the field of organic chemistry due to their role as key intermediates for the synthesis of important compounds such as polymers, dyes, drugs, agrochemicals and pharmaceutical products. Among the various methods reported in literature for the formation of C–N bonds to access secondary anilines, the one-pot reductive amination of aldehydes with nitroarenes is the most interesting procedure, because it allows to obtain diverse N-substituted aryl amines by simple reduction of nitro compounds followed by condensation with aldehydes and subsequent reduction of the imine intermediates. These kinds of tandem reactions are generally catalyzed by transition metal-based catalysts, mainly potentially reusable metal nanoparticles. The rapid growth in the last years in the field of metal-based heterogeneous catalysts for the one-pot reductive amination of aldehydes with nitroarenes demands for a review on the state of the art with a special emphasis on the different kinds of metals used as catalysts and their recyclability features.     

Magnetically Recoverable Catalysts: Catalysis in Synthesis of Polyhydroquinolines

Molecules that contain polyhydroquinoline structural scaffolds are N-containing heterocycles which are of great interest to organic chemists and biologists. Polyhydroquinoline structural scaffolds which are known as calcium channel blockers have emerged as one of the most important class of drugs used for the treatment of cardiovascular and Alzheimer's diseases. Besides, recovery and reusability of catalysts are important issues to be discussed in modern catalysis research especially in organic synthesis. The concept of magnetically recoverable catalysts has been rapidly developed in recent times. Magnetic separation is an efficient strategy for the rapid separation of catalysts from the reaction medium. Also, an alternative to time-, solvent-, and energy-consuming separation techniques. In this review, we focused on the fabrication, surface-modification and characterization of nanomagnetic materials and their application, as magnetically recoverable catalysts, in the synthesis of polyhydroquinoline structural scaffolds.     

Polymer-supported reagents and catalysts: recent advances in synthetic applications

The current surge in parallel array synthesis for the production of small molecule libraries has generated keen interest in the application of solid-supported reagents and catalysts in solution-phase chemistry. The strategy assimilates the advantages of product isolation and purification of solid-phase organic synthesis with the flexible choice of chemistry from the vast repertoire of solution-phase organic reactions. This review summarizes the significant recent advances in the application of polymer-bound reagents and catalysts in solution-phase synthesis of organic molecules. Multi-step reaction sequences employing sequential use of polymer-supported reagents are also discussed. In view of the earlier review publications on this topic, only the recent literature covering 1998 and 1999 is included.     

Design and Synthesis of Powerful Capsule Catalysts Aimed at Applications in C1 Chemistry and Biomass Conversion

Tandem catalytic reaction is a promising strategy to improve the utilization efficiency of energy and resources. The conventional hybrid catalysts cannot readily realize the precisely controlled synthesis of target products due to the unrestricted, open reaction environment. Assembling the hybrid catalyst with multiple active sites into core‐shell structured capsule catalyst is one of the most effective ways to enhance the selectivity of desired products during a tandem catalysis process, because the core‐shell structure offers a space‐confined reaction field and synergistic effect. This review describes our recent progresses on the design and synthesis of core‐shell structured zeolite capsule catalysts developed for C1 chemistry and biomass conversion. The various synthesis methods for constructing the well‐defined zeolite capsule catalysts are described in detail. The applications of the capsule catalysts in catalysis, including the middle isoparaffins synthesis from syngas, one‐step synthesis of dimethyl ether, and liquid‐phase tandem reaction of glycerol conversion, are discussed, respectively. Our perspectives regarding the challenges and opportunities for future research in the field are also provided.     

Recent Advances in Chiral Guanidine‐Catalyzed Enantioselective Reactions

Chiral guanidines have been widely used as Brønsted base catalysts and phase transfer catalysts in enantioselective reactions. Due to their amendable structure and powerful catalytic ability, they have attracted much interest. Several new catalysts containing a guanidinium moiety have been reported over the past decade and many promising outcomes have been achieved. This article illustrates the progress of chiral guanidine catalysis in asymmetric synthesis from 2009 to 2018. It is an update of a review of the same title published in 2009.     

Crown-ether-modified cyclic dipeptides as supramolecular chiral catalysts

With the objective to develop supramolecular catalysts for useful chemical transformations, we report here a rapid and efficient solid-phase synthesis of novel cyclic dipeptides (crown-CDPs) with a diversity of L-DOPA derived crown ether substituents and stereochemistry. We prepared and characterized 14 crown-CDPs and evaluated their efficiency as supramolecular epoxidation catalysts in a water/hexanes biphasic system. Yields increase significantly in the presence of the crown-CDPs, though enantioselectivity depends on the nature of the substituents. The results reported constitute a useful approach for chiral epoxides of interest and further illustrate the potential of cyclic peptides as supramolecular catalysts.     

Scientific Grounds for the Application of Mechanochemistry to Catalyst Preparation

It is shown that mechanochemical activation is efficient in creating waste-free energy-saving methods for the preparation of hydride catalysts, heteropoly acid catalysts, and catalysts for hydrocarbon decomposition into hydrogen and carbon materials, as well for the syntheses of earlier unknown catalytic systems. The capabilities of the mechanochemical methods are demonstrated on modifying the catalytic properties of catalysts and supports: an increase in the strength and catalytic activity, sorption properties, etc. Adhesion theory applied to melts helps to describe the mechanism of mechanochemical synthesis of catalytic systems.