Aspects Of Green Chemistry Research Articles

A Mild and Selective Method for the Catalytic Hydrodeoxygenation of Cyanurate Activated Phenols in Multiphasic Continuous Flow

A low-energy, high-selectivity approach to the catalytic hydrodeoxygenation of phenols is reported using batch or continuous flow methods to react 3 equiv of phenol with cyanuric chloride then hydrogenolyzing the triarylcyanurate intermediate to give 3 equiv of deoxo aromatic. The use of cyanuric chloride compares favorably with existing activation methods, showing improved scalability, atom efficiency, and economics. The scope of both the activation and hydrogenolysis stages are explored using lignin-related phenols. Initial development has identified that continuous stir tank reactors (CSTRs) enable a multiphasic process for converting guaiacol to anisole and at steady state overcome the catalyst deactivation issues observed in batch, seemingly caused by the cyanurate byproduct. Green chemistry aspects and the potential for industrial adoption are discussed.

Novel amino acid derivatives bearing thieno[2,3-d]pyrimidine moiety down regulate NF-κB in γ-irradiation mediated rat liver injury

A series of different amino acid-bearing thieno[2,3-d]pyrimidine moiety was synthesized via green chemistry aspects incorporating water as a solvent to give 2a–f, which were then acidified to attain the target compounds 3–9. Moreover, a tricyclic imidazothienopyrimidine of the glycine derivative (3) was synthesized to give (10). The title compounds were characterized by FT-IR, Mass, 13C-1HNMR spectroscopy and microanalysis. All the obtained amino acid-derivatives were screened for their post-irradiation protective efficacy in young rats. γ-Irradiation exposure was employed to induce oxidative stress. Radiation triggered significant alterations in the hematologic and blood - biochemical parameters. Further, a significant deterioration of hepatic antioxidant status was observed. Furthermore, a significant elevation of Nuclear Factor-kappa B (NF-κB) protein expression and level, which induced elevation in Cyclooxygenase-2 (COX-2) activity and cytochrome P450 2E1 (CYP2E1) gene expression were detected in hepatic tissues. Additionally, elevated levels of Tumor Necrosis Factor–alpha (TNF-α), and Interleukin-6 (IL-6) were perceived in serum of γ-irradiated young rats. However, most of the newly synthesized derivatives showed significant protective effects against injuries induced by γ-irradiation exposure, via ameliorating the altered hematopoietic system and activity of different biochemical parameters in blood. The results indicate that the antioxidant and anti-inflammatory mechanism of these compounds could be attributed to the significant down-regulation NF-κB protein expression in hepatic tissues. Subsequently, NF-κB could regulate TNF-α and IL-6 levels, COX-2 activity and CYP2E1 gene expression. Methionine derivative 8 was found to be the most active one. ConclusionThese new amino acid-derivatives showed promising outcomes as curative agents against γ-irradiation induced oxidative stress and physiological disturbance in different organs of young animals. Beyond, they may represent a novel selective class for treating liver injury induced by γ-irradiation in young rats, via down-regulation of NF-κB expression. Further investigations are warranted prior to the clinical use of these new compounds.

Comparing Amide-Forming Reactions Using Green Chemistry Metrics in an Undergraduate Organic Laboratory

In this laboratory experiment, upper-division undergraduate chemistry and biochemistry majors investigate amide-bond-forming reactions from a green chemistry perspective. Using hydrocinnamic acid and benzylamine as reactants, students perform three types of amide-forming reactions: an acid chloride derivative route; a coupling reagent promoted method; and a boric acid catalyzed condensation. After isolation of the common product, students assess the reactions using the 12 Principles of Green Chemistry and several green chemistry metrics: atom economy; reaction mass efficiency; process mass intensity; and the EcoScale. In addition to assessing what route is the greenest, students also compare the metrics to discern what aspects of green chemistry each metric captures. In order to extend sustainability to economic considerations, the projected “front-end” cost of synthesizing a kilogram of the amide is calculated based on data from each reaction. The experimental work is conducted over two 3 h laboratory pe...

Green Trends in Synthesis of Alkenyl and Alkynyl Chalcogenides

Background: Vinylic and acetylenic chalcogenides have received considerable attention, due to the significant role of these compounds in organic synthesis as versatile building blocks, ligand chemistry, materials science, and biologically relevant processes. Furthermore, these functional groups are found in some important drugs such as (Z)-tamoxifen, which is known as an estrogen antagonist as well as antitumor fredericamycin A. Methods: Therefore, several synthetic methods have been reported in the literature for the preparation of these valuable compounds. Efficeint synthetic protocols based on the green chemistry aspects for the preparation of alkenyl and alkynyl chalcogenides involving the use of benign reaction media and alternative energy resources have been discussed in this review. These processes include examples of coupling reactions, hydrochalcogenation reactions and a variety of reactions mediated by water or recyclable and reusable catalysts. Results: It has been demonstrated that various Csp2 Y and Csp Y (Y = S, Se, Te) bond forming reactions can be successfully carried out with high selectivities and yields in an environmentally friendly fashion. Conclusion: This review focuses on the sustainable and ecofriendly synthetic processes toward alkenyl and alkynyl chalcogenides from readily available alkynes/alkenes and organochalcogens. Moreover, the potential synthetic applications and mechanistic aspects of these transformations are also discussed where appropriate. Keywords: Alkenyl chalcogenides, alkynyl chalcogenides, green reaction media, heterogeneous and homogeneous catalysts, selectivity, sustainable methods.

Highly Selective Synthesis of Carboxamides via Transition Metal Catalysed Aminocarbonylation

This short review summarises the most important results obtained during the past decade in the field of palladium catalysed aminocarbonylation. In this reaction, using amines as N-nucleophiles, the carbonylation of enol-triflates/aryl-triflates or their synthetic surrogates, alkenyl halides/aryl halides takes place resulting in the formation of unsaturated carboxamides or aryl carboxamides. In the latter case, 2-ketocarboxamides are also formed via double carbon monoxide insertion. The efficiency of aminocarbonylation is illustrated by several high-yielding syntheses including transformation of both simple model substrates and skeletons of biological importance. As green chemistry aspects of this reaction, the ambient conditions, high activity, low catalyst loading, the possibility of tuning selectivities and high functional group tolerance should be mentioned. Keywords: Amide, carbonylation, palladium, chemoselectivity, environmentally benign reaction.

Chitosan: An Upgraded Polysaccharide Waste for Organocatalysis

AbstractGreen chemistry, directed towards the sustainable adaptation of human activity, is part of our society. Catalysis and waste upgrading are central aspects of green chemistry. Bringing them together would afford efficient chemical processes from the point of view of sustainability. Chitosan is a polyglucosamine generated from chitin, an abundant polysaccharide recycled from industrial marine wastes. Organocatalysts show some advantages over metallocatalysts in that they do not involve non‐renewable rare metals. However, they have drawbacks such as the need for high loadings and difficulties of recovery. This microreview presents recent achievements in the field of organocatalytic reactions promoted by chitosan as a heterogeneous catalytic material. Various organic reactions are reported, in which chitosan is engaged either as an insoluble organocatalyst or as a support for organocatalysts, being easily recycled and reused. Influences on the reaction outcomes are discussed. Although most reactions produce achiral products, a few asymmetric ones have emerged, demonstrating the capacity of chitosan to transfer its stereochemical information.

Screening for Low-Cost, Efficient and Eco-Friendly Catalysts in Current Green Chemistry Practice: A Test Case with Sodium Formate

Among various green chemistry aspects, selection of catalysts for smooth running of a particular reaction with optimum yield is an important part of the chemical process. In addition to develop novel catalytic systems (homogeneous and heterogeneous catalysts) including nanomaterials and polymer grafting, still there is a tremendous scope in screening commercially available low-cost and less-toxic agents that can carry out an organic transformation of choice in an efficient manner under eco-friendly conditions. Synthetic chemists are engaged to explore this area of interest as one of the current trends in green chemistry, and as a result many such simple chemical entities have now appeared as promising catalysts in effecting a considerable number of organic reactions. Sodium formate is a low-cost commercially available substance which is reported as a less-toxic substance. We have recently demonstrated for the first time that sodium formate can be used as an efficient catalyst for smooth running of some organic transformations under eco-friendly conditions. This article sum-ups our experimental results on the catalytic efficacy of sodium formate as an eco-friendly catalyst in case of certain organic transformations of interest.

Molybdate sulfuric acid-catalyzed one-pot synthesis of substituted coumarins under solvent-free conditions

An efficient method for the synthesis of new aryloylamido coumarins via a one-pot, three-component reaction of an aryl glyoxal, benzamide, and a 4-hydroxycoumarin in the presence of molybdate sulfuric acid under solvent-free conditions is reported. This high yielding reaction is in accordance with green chemistry aspects.

One pot four component sequential synthesis of hexahydroquinoline derivatives in aqueous media via enaminone intermediates: A green protocol

A convenient green chemistry method through one pot four component tandem synthesis of hexahydroquinoline via enaminone intermediate using dimedone, ammonium acetate, aryl aldehydes and malononitrile has been described in aqueous media without the use of any external catalyst. The excess of ammonium acetate used acts as a reagent as well as catalyst. The incorporation of water as solvent along with eradication of external catalyst renders the protocol to comply with the green chemistry aspects. Shorter reaction time, high atom economy, easy work up and purification of products by non-chromatographic method are the crucial features of this methodology. The crystal structure of hexahydroquinoline basically shaped by chromatographic free selective reaction was determined by single crystal X-ray diffraction analysis.

Green Chemistry Starting from 2H-Pyran-2-one Derivatives

In this review with broad coverage of recent literature references we present some general aspects of green chemistry as well as a brief overview of transformations of 2H-pyran-2-ones and fused pyran-2-ones under green condition. The emphasis is given on microwave-assisted transformations under various conditions, such as aqueous condition, neat reactions, reactions in ionic liquids and, to provide a comparison, also the reactions under high pressure are presented. Keywords: Aqueous conditions, high pressure chemistry, ionic liquids, microwave chemistry, neat reactions, 2H-Pyran-2-ones, organocatalysis.

Homogeneous Gold Catalysis – A Hot Spot of Innovation

Lower energy consumption, faster reactions and higher selectivities are some of the intrinsic properties of catalysis. These are important aspects of green chemistry and have made catalysis research one of the key technologies of the 21st century, a very important subject not only for chemists in research and production but also for the whole society. Over the last decade homogeneous gold catalysis has become one of the major innovative areas in catalysis research, continuously providing new catalysis reactions. We have witnessed an initial dominance of methodology development, followed by strong interests in mechanistic studies and catalyst development. In the recent past many new applications in synthesis have been developed, for both natural product synthesis and synthesis of compounds for material science. The catalyst structure is well defined and the manifold of analytical tools of molecular chemistry allows a safe structural assignment of the pre-catalysts, sometimes even of the active catalyst or intermediates of moderate reactivity. Computational chemistry allows a quite precise analysis of the electronic structure of the catalyst, intermediates of the reaction and otherwise inaccessible transition states. Such insights are much more difficult to obtain in the related field of heterogeneous catalysis. In this special issue a collection of publications from leading scientists is presented, covering current hot topics in the field: gold-catalyzed synthesis of heterocycles and polycycles, ligands for gold catalysis, cascade reactions, oxidative CC bond formation and dehydrative reactions.1 A. Stephen K. Hashmi Ruprecht-Karls-Universität Heidelberg Guest Editor

Pyrrole: Chemical Synthesis, Microwave Assisted Synthesis, Reactions and Applications: A Review

Pyrrole is one of the main five membered heterocyclic systems reported for its various chemotherapeutic activities. Subsequently, pyrroles have been highlighted as the important biologically active scaffolds. This review focuses on the synthesis, reactions and pharmacological activity associated with pyrroles, and its derivatives. Microwave-assisted reactions are also covered to understand green chemistry aspects of pyrrole and its derivatives. Various pharmacological applications are discussed critically to assess the importance of the compounds. Keywords: Pyrroles, Microwave synthesis, Applications.

Publishing: will launch in January 2013

The American Chemical Society plans to begin publishing ACS Sustainable Chemistry & Engineering in January 2013. The online-only journal will cover life-cycle assessment, green chemistry, alternative energy, green innovative manufacturing, and harnessing waste as a resource. At the journal’s helm will be Editor-in-Chief David T. Allen, a chemical engineering professor at the University of Texas, Austin, known for his work on urban air quality and reducing pollution. Allen, who is 54, also serves as director of the university’s Center for Energy & Environmental Resources. He earned a B.S. degree in chemical engineering from Cornell University and a Ph.D. in chemical engineering from California Institute of Technology before joining the faculty at UCLA in 1983. He moved to UT Austin in 1995. Allen hopes the journal—which will complement the work of ACS’s Green Chemistry Institute—will be a single, centralized resource for those working on all aspects of green chemistry and sustainability. ...

ChemInform Abstract: How Do the Fine Chemical, Pharmaceutical and Related Industries Approach Green Chemistry and Sustainability?

AbstractReview: 12 refs.

How do the fine chemical, pharmaceutical, and related industries approach green chemistry and sustainability?

Developing manufacturing processes for active pharmaceutical ingredients and intermediates often involves complex chemistry. All companies now aim to uphold the principles of green chemistry and sustainability as far as possible, but how effective are they in achieving this and how much variation is there from company to company? This perspective discusses the results of a survey carried out with 24 companies, including 11 “big pharma” companies and 6 “other pharma” companies. Companies from outside the pharma sector were also included to give a comparison with other areas of the fine chemical industry. These included two fine chemical manufacturers, one agrochemical manufacturer, and one flavour and fragrance company. The survey covered organisational aspects of green chemistry and sustainability, such as corporate policy and policy implementation, green chemistry and technologies, process metrics, and how the application of green issues changes through the various stages of development and whether there are different standards for low volume and/or high potency compounds.

Methylation of 2-Naphthol Using Dimethyl Carbonate under Continuous-Flow Gas-Phase Conditions

This experiment investigates the methylation of 2-naphthol with dimethyl carbonate. The volatility of the substrates, products, and co-products allows the reaction to be performed using a continuous-flow gas-phase setup at ambient pressure. The reaction uses catalytic quantities of base, achieves high conversion, produces little waste, and demonstrates many other fundamental aspects of green chemistry.

A clean and effective supercritical carbon dioxide method for the host–guest synthesis and encapsulation of photoactive molecules in nanoporous matrices

The present work is concerned with host–guest processes in the micro- and mesoporous restricted spaces provided by silica aerogels and aluminosilicates. A supercritical carbon dioxide ship-in-a-bottle approach was used for the synthesis of photoactive molecules (triphenylpyrylium and dimethoxyltrityl cations) inside these nanoporous matrices. The resulting hybrid nanocomposites can act as stable and recoverable heterogeneous photocatalysts, having obvious advantages with respect to the more easily degraded organic cations frequently used in homogeneous catalysis. Two aspects of green chemistry are combined in this study to produce nanoporous materials loaded with cationic photosensitizers: (i) the use of supercritical carbon dioxide as a reaction medium in one-pot and as a zero waste technology, and (ii) the use of transparent high surface area nanoporous supports that are expected to be more effective for the target photoactive applications than traditional opaque microporous matrices.

Green analytical chemistry—theory and practice

This tutorial review summarises the current state of green analytical chemistry with special emphasis on environmentally friendly sample preparation techniques. Green analytical chemistry is a part of the sustainable development concept; its history and origins are described. Miniaturisation of analytical devices and shortening the time elapsing between performing analysis and obtaining reliable analytical results are important aspects of green analytical chemistry. Solventless extraction techniques, the application of alternative solvents and assisted extractions are considered to be the main approaches complying with green analytical chemistry principles.

Metal-Free Intramolecular Aziridination of Alkenes Using Hypervalent Iodine Based Sulfonyliminoiodanes

Intramolecular aziridination of alkenyl sulfonyliminoiodanes occurs thermally in the absence of conventional metal catalysts such as Rh(II) and Cu(II). In rigid molecular systems, conversions are near quantitative. The scope of the nonmetal process is related to the conformational flexibility of the alkenyl sulfonyliminoiodane. A mechanism is proposed involving formal 2 + 2 cycloaddition of the RSO(2)N=IPh group to the double bond followed by reductive elimination of PhI to yield the sulfonylaziridine. Green chemistry aspects of the process are highlighted.

Highly efficient aerobic ruthenium-catalyzed oxidative cross-dehydrogenative coupling for sp3–sp3 carbon–carbon bond formation

A highly efficient sp3–sp3 carbon–carbon bond formation system was developed for the aerobic ruthenium-catalyzed oxidative cross-dehydrogenative coupling reaction between tertiary amines and sp3 C–H compounds in the presence of RuCl3/O2, thus giving the corresponding α-functionalized amines. Compared with the reported method, H2O2 or tBuOOH was replaced successfully by economical and facile oxygen as the oxidant. Three types of activated C–H bonds for pronucleophiles were evaluated in this system. All these features combined are in accordance with important prospective green chemistry aspects.