Organic Reactions In Aqueous Media Research Articles

Benchmarking Cationic Monolayer Protected Nanoparticles and Micelles for Phosphate-Mediated and Nucleotide-Selective Proton Transfer Catalysis.

Both micelles and self-assembled monolayer (SAM)-protected nanoparticles are capable of efficiently hosting water-immiscible substrates to carry out organic reactions in aqueous media. Herein, we have analyzed the different catalytic effect of SAM-protected cationic nanoparticles and cationic surfactants of varying chain length towards base-catalyzed proton transfer mediated ring-opening reaction of 5-nitrobenzisoxazole (NBI) (also known as Kemp Elimination (KE) reaction). We use inorganic phosphate ion or different nucleotide (phosphate-ligated different nucleoside) as base to promote the reaction on micellar or nanoparticle interface. We find almost 2-3 orders of magnitude higher concentration of surfactants of comparable hydrophobicity required to reach the similar activity which attained by low cationic head group concentration bound on nanoparticle. Additionally, at low concentration of nanoparticle-bound surfactant or with high surfactant in micellar form, nucleotide-selectivity has been observed in activating KE reaction unlike free surfactant at low concentration. Finally, we showed enzyme-mediated nucleotide hydrolysis to generate phosphate ion which in situ upregulate the KE activity much more in GNP-based system compared to CTAB. Notably, we show a reasonable superiority of SAM-protected nanoparticles in activating chemical reaction in micromolar concentration of headgroup which certainly boost up application of SAM-based nanoparticles not only for selective recognition but also as eco-friendly catalyst.

Polymeric architecture as a tool for controlling the reactivity of palladium(II) loaded nanoreactors.

Self-assembled systems, like polymeric micelles, have become great facilitators for conducting organic reactions in aqueous media due to their broad potential applications in green chemistry and biomedical applications. Massive strides have been taken to improve the reaction scope of such systems, enabling them to perform bioorthogonal reactions for prodrug therapy. Considering these significant advancements, we sought to study the relationships between the architecture of the amphiphiles and the reactivity of their PdII loaded micellar nanoreactors in conducting depropargylation reactions. Towards this goal, we designed and synthesized a series of isomeric polyethylene glycol (PEG)-dendron amphiphiles with different dendritic architectures but with an identical degree of hydrophobicity and hydrophilic to lipophilic balance (HLB). We observed that the dendritic architecture, which serves as the main binding site for the PdII ions, has greater influence on the reactivity than the hydrophobicity of the dendron. These trends remained constant for two different propargyl caged substrates, validating the obtained results. Density functional theory (DFT) calculations of simplified models of the dendritic blocks revealed the different binding modes of the various dendritic architectures to PdII ions, which could explain the observed differences in the reactivity of the nanoreactors with different dendritic architectures. Our results demonstrate how tuning the internal architecture of the amphiphiles by changing the orientation of the chelating moieties can be used as a tool for controlling the reactivity of PdII loaded nanoreactors.

Multi‐Compartmentalized Cellulose Macrobead Catalysts for In Situ Organic Reaction in Aqueous Media

This study reports a promising approach to fabricate bacterial cellulose (BC)-based macrobead catalysts with improved catalytic activities and recyclability for organic reactions in aqueous media. To this end, the consecutive extrusion and gelation of BC precursor fluids is conducted using a combined micronozzle device to compartmentalize the resulting BC macrobeads in a programmed manner. The use of BCs laden with Au and Pd nanoparticles (NPs), and Fe3 O4 NPs led to the production of catalytically and magnetically compartmentalized BC macrobeads, respectively. Through the model reduction reaction of 4-nitrophenol to 4-aminophenol using NaBH4 , it is finally demonstrated that the BC macrobead catalysts not only enhance catalytic activities while exhibiting high reaction yields (>99%) in aqueous media, but also repeatedly retrieve the products with ease in response to the applied magnetic field, enabling the establishment of a useful green catalyst platform.

“ON-WATER” RING OPENING REACTIONS: A REVIEW

The replacement of current organic chemical processes with more environmentally benign alternatives is an important goal from an ecological point of view. The study is aimed with the goal of promoting water as a solvent in organic synthesis. In recent years, extensive industrial and scholarly research has been promoted for the development of organic reactions in aqueous media. Using water as a solvent often promotes considerable rate enhancements and operational simplicity. Environmental benefits of using water are additionally highlighted in relation to the Twelve Principles of Green Chemistry.

Tuning the Reactivity of Micellar Nanoreactors by Precise Adjustments of the Amphiphile and Substrate Hydrophobicity.

Polymeric assemblies, such as micelles, are gaining increasing attention due to their ability to serve as nanoreactors for the execution of organic reactions in aqueous media. The ability to conduct organic transformations, which have been traditionally limited to organic media, in water is essential for the further development of important fields ranging from green catalysis to bioorthogonal chemistry. Considering the recent progress that has been made to expand the range of organometallic reactions conducted using nanoreactors, we aimed to gain a deeper understanding of the roles of the hydrophobicity of both the core of micellar nanoreactors and the substrates on the reaction rates in water. Toward this goal, we designed a set of five metal-loaded micelles composed of polyethylene glycol–dendron amphiphiles and studied their ability to serve as nanoreactors for a palladium-mediated depropargylation reaction of four substrates with different log P values. Using dendrons as the hydrophobic block, we could precisely tune the lipophilicity of the nanoreactors, which allowed us to reveal linear correlations between the rate constants and the hydrophobicity of the amphiphiles (estimated by the dendron’s cLog P). While exponential dependence was obtained for the lipophilicity of the substrates, a similar degree of rate acceleration was observed due to the increase in the hydrophobicity of the amphiphiles regardless of the effect of the substrate’s log P. Our results demonstrate that while increasing the hydrophobicity of the substrates may be used to accelerate reaction rates, tuning the hydrophobicity of the micellar nanoreactors can serve as a vital tool for further optimization of the reactivity and selectivity of nanoreactors.

Organic reactions in aqueous media catalyzed by nickel

This review highlights the nickel-catalyzed organic reactions in aqueous media with special focus on the mechanistic course of catalytic reactions and their applications.

Proline‐derived Long‐aliphatic‐chain Amphiphilic Organocatalysts (PDLACAOs) for Asymmetric Reactions in Aqueous Media

AbstractHerein, a specialized review of the origin and state of the art of proline‐derived long‐aliphatic‐chain amphiphilic organocatalysts (PDLACAOs) and their use in asymmetric organic reactions in aqueous media (water, brine, and sea water), including in water and in the presence of water, is presented. The reactions in which they have been evaluated and the most important mechanisms are discussed.

Design of Carbon-carbon and Carbon-heteroatom Bond Formation Reactions under Green Conditions

:The development of C-C and C-heteroatom (C-N, C-O and C-P) bond reactions is a field of significant interest and has received momentous attention in modern organic chemistry. These reactions have been exploited in the synthesis of pharmaceuticals, agrochemicals and molecules of interest in materials science. With the increasing awareness of global warming and the use of renewable energies, it is of paramount importance to reduce the usage of hazardous chemicals in both industrial and academic research and to achieve a healthier environment through green practices. Green chemistry is a rapidly emerging approach that shows us a path for the sustainable growth of future science and technologies. In the recent past, healthy growth has been recorded in a number of organic reactions in aqueous media, which are environment-friendly and energy conserving. This review documents the literature on the development of green methodologies involving the design of C-C, C-O, C-N and C-P bond formations of coupling and condensed reactions. It emphasizes the exceptional practices and important advances achieved using alternative green tools, such as microwave (MW), high-speed ball milling (HSBM) and ultrasound irradiation techniques, and a variety of reusable catalysts and green solvents, with attention to water.

“Water soluble” palladium nanoparticle engineering for C–C coupling, reduction and cyclization catalysis

Water stable Pd-NPs prepared in an eco-friendly manner enable highly efficient catalysis of 6 organic reactions in aqueous media with quantities of Pd down to the ppm level and high turnover frequencies.

One-Pot Combination of Metal- and Bio-Catalysis in Water for the Synthesis of Chiral Molecules

During the last decade, the combination of different metal- and bio-catalyzed organic reactions in aqueous media has permitted the flourishing of a variety of one-pot asymmetric multi-catalytic reactions devoted to the construction of enantiopure and high added-value chemicals under mild reaction conditions (usually room temperature) and in the presence of air. Herein, a comprehensive account of the state-of-the-art in the development of catalytic networks by combining metallic and biological catalysts in aqueous media (the natural environment of enzymes) is presented. Among others, the combination of metal-catalyzed isomerizations, cycloadditions, hydrations, olefin metathesis, oxidations, C-C cross-coupling and hydrogenation reactions, with several biocatalyzed transformations of organic groups (enzymatic reduction, epoxidation, halogenation or ester hydrolysis), are discussed.

Synthesis of (E)‐3‐Styrylquinolin‐4(1H)‐ones in Water by Ohmic Heating: a Comparison with Other Methodologies

Ohmic heating offers a very efficient way to perform organic reactions in aqueous media. Potentially bioactive (E)‐3‐styrylquinolin‐4(1H)‐ones were synthesized by the Heck reaction of 3‐iodo‐1‐methylquinolin‐4(1H)‐one with styrenes in water and with ohmic heating. Pd(OAc)2 was used as catalyst, and tetrabutylammonium bromide was used as phase‐transfer catalyst in the presence of an inorganic base. Comparison with other established procedures highlight the benefits of this new methodology.

Efficient synthesis of α,β-unsaturated ketones with trans-selective Horner–Wadsworth–Emmons reaction in water

Organic reactions in aqueous media are being developed because water is environmentally benign. The Horner–Wadsworth–Emmons reaction is a modified Wittig reaction for the synthesis of α,β-unsaturated ketones and other conjugated compounds. Here we prepared high molecular weight ketones by the Horner–Wadsworth–Emmons reaction of dimethyl-2-oxopropylphosphonate and various aldehydes in water at room temperature. The product was precipitated during the reaction process and was separated readily by a simple filtration in 90–99 % yield.

Recent Advances in Stereoselective Organic Reactions in Aqueous Media

Review: [recent advances in stereoselective reactions such as aldol, Mannich, allylatio, hydrogenation, Michael, Heck, oxidation-reduction in aqueous media; 213 refs.] .

Invoking pairwise interactions in water-promoted Diels-Alder reactions by using ionic liquids as cosolvents.

Rate constants and derived activation parameters of organic reactions in aqueous media, in particular Diels-Alder reactions, are sensitive to the presence of cosolvents in water. To enhance the solubility window of water, we introduced ionic liquids as cosolvents in the aqueous Diels-Alder reaction between anthracene-9-carbinol and N-ethylmaleimide. The reactive potentials of the organic compounds are parameterized by using semi-empirical quantum chemical methods. The principle of Savage-Wood additivity of group interactions is used to quantify the pairwise group interactions among chemically inert ionic liquids and organic reactants, both at initial and transition states of the reaction. The present approach shows promise, as the use of simple calculations from easily available kinetic data can help researchers to understand the versatility of green ionic-liquid alternatives to volatile organic solvents.

Synthesis and Evaluation of a Photochromic Surfactant for Organic Reactions in Aqueous Media

A novel photochromic azobenzene-based surfactant was described for organic chemistry in water. The molecule 4-butylazobenzyl-4'-triazologlucuronic acid sodium salt thus synthesized can be isomerized from its trans to its cis form reversibly in solution by simple light irradiation. That property allowed the recyclability of a model acetylation reaction performed in the surfactant media, compared to the well-known, commercially available sodium dodecyl sulfate surfactant media.

Ultrasound Irradiated Synthesis of Bis-pyrimidine Derivative in Aqueous MediA

Pyrimidine derivatives have been found to possess a broad spectrum of biological activities. Among various pyrimidine derivatives, bis-pyrimidine seems to be the rarely studied. A variety of methods have been reported for the preparation of this class of compound. However, in spite of their potential utility, some of the reported methods suffer from drawbacks such as long reaction times, cumbersome product-isolation procedures, and environmental concerns. Organic reactions in aqueous media have attracted increasing interest recently because of environmental issues and the understanding of biochemical processes. Ultrasound has increasingly been used in organic synthesis for greater yields, shorter reaction times or milder conditions.

Synthesis and Biological Evaluation of New 1-H-3 (4'-Hydroxyphenyl)- 5-Aryl-2-Pyrazoline Derivatives

Organic reactions in aqueous media have attracted increasing interest recently because of environmental issues and the understanding of biochemical processes. In the present investigation eight new pyrazoline derivatives were synthesized by condensing different hydroxyl chalcones with hydrazine hydrate in dilute ethanolic potassium hydroxide or sodium hydroxide solution at room temperature according to Claisen- Schmidt condensation reaction. All these compounds were characterized by IR and NMR spectral data. These synthesized compounds were screened for pharmacological activity such as antimicrobial and anthelmintic activity.

A review of aqueous organic reactions for the undergraduate teaching laboratory

This article summarizes the wide scope of aqueous organic reactivity from a pedagogical perspective. It is aimed at university instructors with the goal of promoting water as a solvent in academic institutions. Recently, extensive industrial and scholarly research has concerned development of organic reactions in aqueous media. Many examples are now possible in the student laboratory including carbon–carbon/carbon–nitrogen bond-forming reactions and functional group transformations (e.g. oxidations, reductions, and halohydrations). Experiments are summarized from the educational literature (journal articles and laboratory textbooks) and their green features are described. Using water as solvent often promotes significant rate enhancements and operational simplicity – both of importance when training undergraduates during limited laboratory time. Environmental benefits of using water are additionally highlighted to students’ first hand in relation to the Twelve Principles of Green Chemistry.

Peptide Synthesis in Aqueous Environments: The Role of Extreme Conditions on Amino Acid Activation

The free energy surfaces and reaction mechanisms underlying the activation of amino acids by COS in bulk water at ambient conditions as well as extreme temperature-pressure thermodynamic conditions were studied using accelerated ab initio molecular dynamics. The results for the reaction sequence leading from glycine to its activated form, a so-called Leuchs anhydride or alpha-amino acid N-carboxyanhydride (NCA), suggest that extreme conditions not far from the critical point of water may favor the formation of this activated species. This is traced back to appropriately affecting relative stabilities of neutral versus charged or zwitterionic molecular species which shifts equilibria, affects relative barriers, and thus modifies reaction rates. Furthermore, it is shown that the N-carboxyanhydride of glycine is not formed from N-thiocarboxyl glycine by its direct cyclization, but instead an indirect mechanism, the so-called isocyanate route, is clearly preferred at both conditions. The work quantitatively underpins the impact of extreme solvent conditions on the investigated organic reactions in aqueous media which implies that the presented results are of relevance to fields such as prebiotic chemistry and green chemistry.

ChemInform Abstract: Recent Advances in Bismuth‐Catalyzed Organic Synthesis

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