Diels-Alder Reaction In Water Research Articles

Modelling chemical processes in explicit solvents with machine learning potentials

Solvent effects influence all stages of the chemical processes, modulating the stability of intermediates and transition states, as well as altering reaction rates and product ratios. However, accurately modelling these effects remains challenging. Here, we present a general strategy for generating reactive machine learning potentials to model chemical processes in solution. Our approach combines active learning with descriptor-based selectors and automation, enabling the construction of data-efficient training sets that span the relevant chemical and conformational space. We apply this strategy to investigate a Diels-Alder reaction in water and methanol. The generated machine learning potentials enable us to obtain reaction rates that are in agreement with experimental data and analyse the influence of these solvents on the reaction mechanism. Our strategy offers an efficient approach to the routine modelling of chemical reactions in solution, opening up avenues for studying complex chemical processes in an efficient manner.

Study and optimization of Diels-Alder reaction of piperine in aqueous ionic solutions using Gn.HCl as a catalyst

Study and optimization of Diels-Alder reaction of piperine in aqueous ionic solutions using Gn.HCl as a catalyst

Direct grafting imidazolium-based poly(ionic liquid) onto multiwalled carbon nanotubes via Diels-Alder “click” reaction

ABSTRACTA facile route for grafting poly(ionic liquid)s (PILs) on to the surface of multi-walled carbon nanotubes (MWNTs) was demonstrated via Diels-Alder (DA) “click” reaction. Firstly, block copolymers of poly(chloromethylstyrene-alt-maleic anhydride) (PCMA) were prepared by the reversible addition-fragmentation chain transfer (RAFT) polymerization. The anhydride units in the copolymer were functionalized with furfuryl amine and then the chloromethyl groups were subsequently tailored with 1-methylimidazole, which afforded imidazolium-based PILs bearing pendent furan moieties. The PILs chains were covalently anchored to the surface of MWNTs, affording PILs/MWNTs by the DA reaction in water under ultrasound assistance. The obtained hybrid materials were characterized by TGA, FT-IR, and TEM analysis. The PILs/MWNTs could be well dispersed in water and organic solvents for several months.

Ultrasound-promoted direct functionalization of multi-walled carbon nanotubes in water via Diels-Alder “click chemistry”

A facile and environmentally friendly strategy for grafting polymers onto the surface of multi-walled carbon nanotubes (CNTs) was demonstrated by Diels-Alder “click chemistry”. Firstly, the copolymers of poly(styrene-alt-maleic anhydride) (PSM) were prepared by the reversible addition-fragmentation chain transfer (RAFT) polymerization and subsequently functionalized with furfuryl amine to introduce anchoring groups. The copolymers were then grafted on CNTs via the Diels-Alder reaction in water through a conventional heating-stirring route and ultrasound-assisted method. The obtained nanocomposite materials were characterized by thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. The results indicated that the reaction rate under ultrasound irradiation was accelerated about 12 times than the one under the conventional heating-stirring condition without losing the grafting efficiency. The direct functionalization of CNTs formed a stably dispersed solution in water, promising a green and effective method for industrial process.

Solid-supported DNA for asymmetric synthesis: a stepping-stone toward practical applications.

We developed an affordable solid-supported DNA and demonstrated that it could be used as a reusable chiral source for the copper(ii)-catalyzed Diels-Alder reaction in water. This study will be a valuable stepping-stone for the industrial application of DNA-based asymmetric synthesis.

Fabrication of Supramolecular Structured Hydrogels Based on Diels-Alder Click Reaction

A novel kind of supramolecular structrued hydrogels were fabricated by Diels-Alder click reaction between furan-functionalized polypseudorotaxanes and polymeric dienophiles. Firstly, polypseudorotaxanes were prepared by supramolecular self-assembly of furan-terminated poly(ethylene glycol)(PEG) and α-cyclodextrins (CDs) in water. And polymeric dienophiles were synthesized by a coupling reaction between copolymer of hydroxyethyl methacrylate and N,N-dimethyl acrylamide and N-maleoyl alanine (AMI). The supramolecular structured hydrogels were prepared by Diels-Alder reaction in water.

ChemInform Abstract: Diels-Alder Reactions in Aqueous Solutions. Enforced Hydrophobic Interactions Between Diene and Dienophile.

Second-order rate constants and isobaric activation parameters for the intermolecular Diels-Alder reactions of cyclopentadiene with alkyl vinyl ketones (2a,b) and 5-substituted-1,4-naphthoquinones (3a-c) as well as for the intramolecular Diels-Alder reaction of N-furfuryl-N-methylmaleamic acid (4) were determined in water, monohydric alcohols, and highly aqueous solutions containing monohydric alcohols and other organic cosolvents. The intermolecular as well as the intramolecular Diels-Alder reaction are characterized by large rate accelerations upon going from an organic solvent to water as the reaction medium. A model for solvation effects on rate constants for Diels-Alder reactions in aqueous solutions is developed. The typical, huge rate enhancements for Diels-Alder reactions in water and in highly aqueous binary mixtures are significantly sensitive to substituent effects and are discussed in terms of enforced pairwise hydrophobic interactions between diene and dienophile.

Aqueous Ti(IV)-Catalyzed Diels-Alder Reaction

The aqueous Diels-Alder reaction of 1,3-cyclohexadiene with 1,4-benzoquinone was compared and contrasted to the same reaction catalyzed with Flextyl P, a novel Ti(IV) performance catalyst. The catalyst improved conversion by 22% versus the uncatalyzed reaction and represents a rare example of a Ti(IV) catalyzed Diels-Alder reaction in water.

α,β-Unsaturated 2-Acyl Imidazoles as a Practical Class of Dienophiles for the DNA-Based Catalytic Asymmetric Diels−Alder Reaction in Water

Alpha,beta-unsaturated 2-acyl imidazoles are a novel and practical class of dienophiles for the DNA-based catalytic asymmetric Diels-Alder reaction in water. The Diels-Alder products are obtained with very high diastereoselectivities and enantioselectivities in the range of 83-98%. The catalytic reaction was performed on a 1.0 mmol scale, and the imidazole auxiliary was removed readily.

Environmentally Benign Solvent Systems: Toward a Greener [4+2] Cycloaddition Process

Green chemistry is a field that encompasses a wide range of environmentally benign technologies. This review discusses the principles of green chemistry, as well as recent applications of these principles to the Diels-Alder reaction, with a focus on benign solvent systems. Specifically, Diels-Alder reactions in water, ionic liquids, supercritical carbon dioxide, and solvent-free systems will be reviewed up to February 2006. Keywords: Diels-Alder chemistry, green chemistry, benign solvents

Highly enantioselective DNA-based catalysis

A new approach to DNA-based asymmetric catalysis is presented, which gives rise to very high enantioselectivities (up to 99% ee) in the copper catalyzed Diels-Alder reaction in water.

ChemInform Abstract: Diels—Alder Reactions in Water

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Effects of Lewis acid-surfactant-combined catalysts on aldol and Diels-Alder reactions in water

Aldol and Diels-Alder reactions in water in the presence of various dodecyl sulfate and dodecanesulfonate salts as Lewis acid-surfactant-combined catalysts have been studied. In the aldol reactions, these salts differed from each other with respect to their catalytic ability at the initial stage of the reaction and to the final yields of the aldol product, while these salts did not affect the reaction rates of the Diels-Alder reactions. These results disclose the remarkable characteristics of Lewis acid catalysis in water.

A Chiral Lewis-Acid-Catalyzed Diels−Alder Reaction. Water-Enhanced Enantioselectivity

A Chiral Lewis-Acid-Catalyzed Diels−Alder Reaction. Water-Enhanced Enantioselectivity

Combined quantum chemical and MM-approach to the endo/exo selectivity of diels-alder reactions in polar media

The endo/exo selectivity of Diels-Alder reactions in water and methanol is studied with semiempirical methods using the SCRF approach and a combined quantum chemical (transition state) and molecular mechanics (solvent molecules) method (QC/MM) to determine the effect of protic solvents on the transition state energies. Evidently, the number of hydrogen bonds that causes strong Coulomb interaction, discriminates heats of formation of transition states. The results indicate that the s-cis/s-trans conformation of acrylates controls the endo/exo selectivity.

Solvent Effects on a Diels-Alder Reaction Involving a Cationic Diene: Consequences of the Absence of Hydrogen-Bond Interactions for Accelerations in Aqueous Media.

In order to study the influence of hydrogen-bond interactions on the accelerations of Diels-Alder reactions in water and highly aqueous mixed solvent systems, second-order rate constants for the Diels-Alder reaction of acridizinium bromide (1a) with cyclopentadiene (CP) have been measured in aqueous media and organic solvents. Only modest rate accelerations were found in water-rich media. This is attributed to the absence of hydrogen-bonding groups in the reactants. Comparison with cycloadditions of CP with 9-carbomethoxyacridizinium bromide (1b), acrylonitrile (3), and methyl vinyl ketone (4), which do contain hydrogen-bond acceptors, reveals substantially larger aqueous accelerations. These results demonstrate that hydrogen bonding is a major factor in aqueous accelerations. Also rate constants for the cycloaddition of CP to 1a in surfactant solutions were determined. Micellar catalysis is observed in SDS solutions, due to binding of both the diene and the dienophile to the anionic micellar surface.

Lewis-acid catalysis of a Diels-Alder reaction in water

The reaction between the diene 1 and cyclopentadiene ( 2) is efficiently catalysed by small amounts of Lewis acids (Co 2+, Ni 2+, Cu 2+, Zn 2+). The reaction in an aqueous solution containing 0.010 M Cu(NO 3) 2 is 250.000 times faster than that in acetonitrile. This huge acceleration is the result of a combination of the accelerative solvent effect of water and catalysis by Cu 2+ as the Lewis acid.

Diels-Alder reactions in water: Enforced hydrophobic interaction and hydrogen bonding

Abstract

Diels-Alder Reactions in Water. Effects of Hydrophobicity and Hydrogen Bonding

In order to check whether the activated complex for the Diels-Alder reactions of 5-substituted 1,4-naphthoquinones with cyclopentadiene is more polar in water than in other solvents, we have determined the substituent effects in seven different solvents. The substituent effects gradually decrease with increasing rate of the reaction in a specific solvent, indicating that the charge separation in the activated complex in water is not much different from that in the other solvents. We also compared solvent effects on the Diels-Alder reaction of methyl vinyl ketone with cyclopentadiene with effects on the corresponding reaction of methyl vinyl sulfone. The medium effects were separated into effects on initial state and activated complex. The destabilization of the initial state by water and the stabilization of the activated complex by 2,2,2-trifluoroethanol were less pronounced for the sulfone than for the ketone. These results further underline the importance of enforced hydrophobic interactions and changes in hydrogen bonding during the activation process in explaining the acceleration of Diels-Alder reactions in water.

Initial-state and transition-state effects on Diels-Alder reactions in water and mixed aqueous solvents

Initial-state and transition-state effects on Diels-Alder reactions in water and mixed aqueous solvents