Olefins In Water Research Articles

Facile Pd-catalyzed chemoselective transfer hydrogenation of olefins using formic acid in water

An effective Pd-catalyzed reduction of olefins in water using formic acid is disclosed. A wide range of saturated hydrocarbons are obtained with an excellent conversion and remarkable chemoselectivity under mild reaction conditions. This protocol is more advantageous and less cumbersome owing to the use of HCOOH as a hydrogen source, water as a solvent, and simple workup procedure.

Olefin Epoxidation in Aqueous Phase Using Ionic-Liquid Catalysts.

Hydrophobic imidazolium-based ionic liquids (IL) act as catalysts for the epoxidation of unfunctionalized olefins in water using hydrogen peroxide as oxidant. Although the catalysts are insoluble in both the substrate and in water, surprisingly, they are very well soluble in aqueous H2 O2 solution, owing to perrhenate-H2 O2 interactions. Even more remarkably, the presence of the catalyst also boosts the solubility of substrate in water. This effect is crucially dependent on the cation design. Hence, the imidazolium perrhenates enable both the transfer of hydrophobic substrate into the aqueous phase, and serve as actual catalysts, which is unprecedented. At the end of the reaction and in absence of H2 O2 the IL catalyst forms a third phase next to the lipophilic product and water and can easily be recycled.

Micelle-based nanoreactors containing Ru-porphyrin for the epoxidation of terminal olefins in water

This contribution introduces a strategy to use Ru(II)-porphyrin complexes as catalysts for the epoxidation of alkenes in water. The design is based on shell cross-linked micelle-based nanoreactors with hydrophobic cores and hydrophilic shells as supports for the Ru(II) porphyrin complexes. The supported complexes are efficient catalysts for oxidation reactions, specifically the selectively oxidation of alkenes to epoxides. The presented strategy is the first system that allows for running Ru-catalyzed epoxidation reactions in water.

Recyclable, green and efficient epoxidation of olefins in water with hydrogen peroxide catalyzed by polyoxometalate nanocapsule

A practical method for the selective epoxidation of alkenes was discovered using HxPMo12O40⊂H4Mo72Fe30(CH3COO)15O254 as a catalyst in the presence of H2O2 as a green oxidant. However, the simple catalyst system involving polyoxometalates and H2O2 exercised the most successful system in obtaining high to excellent yields of epoxide products for different alkenes, including aromatic and aliphatic alkenes at room temperature in water. The effectiveness of this catalyst is evidenced by 99% selectivity to epoxide and 97–99% efficiency of H2O2 utilization. The stability of PMo⊂Mo72Fe30 under a catalytic reaction has been confirmed by XRD, FT-IR and Raman spectroscopies.

Hydrogel supported chiral imidazolidinone for organocatalytic enantioselective reduction of olefins in water

AbstractChiral products play an important role particularly in the field of medicinal chemistry, where it is known that enantiomers often have very different biological properties and effects. One of the most powerful tool to obtain a product as a single enantiomer is asymmetric catalysis. Recently, organocatalysis, i.e. the use of small organic molecules to catalyze enantioselective transformations, has emerged as a prominent field in asymmetric synthesis. In this work, the use of hydrogels as a support for a chiral imidazolidinone organocatalyst (MacMillan catalyst) and its application in the reduction of activated olefins mediated by the Hantzsch ester is reported for the first time. Results showed a good activity of hydrogels in respect to both yield and enantioselection.

ChemInform Abstract: Chiral Rh Phosphine—Phosphite Catalysts Immobilized on Ionic Resins for the Enantioselective Hydrogenation of Olefins in Water.

AbstractHigh conversions and high enantioselectivities are obtained in the hydrogenation of acrylates of type (I) using a chiral rhodium catalyst immobilized on an ionic resin.

Chiral Rh phosphine–phosphite catalysts immobilized on ionic resins for the enantioselective hydrogenation of olefins in water

Rh phosphine–phosphite chiral catalysts immobilized on ion exchange resins provide highly enantioselective hydrogenation of enamides in water.

ChemInform Abstract: Catalytic Epoxidation Activity of Keplerate Polyoxomolybdate Nanoball Toward Aqueous Suspension of Olefins under Mild Aerobic Conditions.

AbstractThe catalytic efficiency of a sphere‐shaped nanosized polyoxomolybdate in the aerobic epoxidation of olefins in water is studied.

Catalytic Epoxidation Activity of Keplerate Polyoxomolybdate Nanoball toward Aqueous Suspension of Olefins under Mild Aerobic Conditions

Catalytic efficiency of a sphere-shaped nanosized polyoxomolybdate {Mo132} in the aerobic epoxidation of olefins in water at ambient temperature and pressure in the absence of reducing agent is exploited which resulted good-to-high yields and desired selectivity.

Pd nanoparticles confined in fluoro-functionalized yolk-shell-structured silica for olefin hydrogenation in water

Pd nanoparticles were confined in yolk-shell mesoporous silica via encapsulation, etching and modification, producing a functionalized yolk-shell-structured catalyst. This catalyst was characterized using X-ray diffraction analysis, transmission electron microscopy, N 2 adsorption-desorption, and thermogravimetric analysis. The catalyst had high activity for olefin hydrogenation in water, higher than that of the unmodified counterpart. The catalyst can be recovered through centrifugation, and its activity is not significantly decreased after several reaction cycles. 先将Pd纳米粒子负载于SiO 2 球表面上, 再经包裹/刻蚀/硅烷化修饰, 得到氟丙基功能化“蛋黄”型结构催化剂. 并采用X射线衍射/透射电镜/N 2 吸附-脱附和热重等对催化剂进行了表征. 结果表明, 该催化剂在水相烯烃加氢反应中表现出较高的活性, 明显高于未经氟丙基修饰的同类催化剂. 该催化剂通过离心便可实现回收, 多次循环使用后仍保持较高的活性. The fluoro-functionlized yolk-shell-structured catalyst (yPd@mSiO 2 -F) exhibited higher activity than the non-functionlized catalyst (yPd@mSiO 2 ) in the hydrogenation of olefins in water.

Diastereoselective [2+2] Photocycloaddition of Chiral Cyclic Enones with Olefins in Aqueous Media Using Surfactants

We conducted diastereodifferentiating [2+2] photocycloadditions of cyclo-hexenones modified with a chiral 8-(p-methoxy phenyl)menthyl auxiliary with olefins in water. Although the photoreaction didn’t proceed at all in pure water owing to very low solubility, the use of surfactants [sodium dodecyl sulfate (SDS) or dodecylamine hydrochloride (DAH)] and additive (organic solvent) enabled the reactions to progress with moderate to high conversions and yields. Furthermore, we synthesized a new menthol derivative substrate containing a (p-octyloxy)phenyl group for enhancing hydrophobicity, and elucidated that this new substrate was found to be a suitable chiral auxiliary in this asymmetric photoreaction in aqueous system. The additive effect of organic molecules on the yield and diastereoselectivity of the photo-adducts is also discussed.

Modified crosslinked polyacrylamide anchored Schiff base–cobalt complex: A novel nano-sized heterogeneous catalyst for selective oxidation of olefins and alkyl halides with hydrogen peroxide in aqueous media

A new nano-sized polymer-supported Schiff base–cobalt complex catalyst based on crosslinked polyacrylamide was synthesized and characterized. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of the catalyst show nanosize fiber-like image of the polymeric catalyst. The catalyst activity was studied in the oxidation of various olefins including non-activated terminal olefin in water with hydrogen peroxide as an oxygen source. The catalyst showed high degree of selectivity. The effects of reaction parameters such as solvent, oxidant, temperature, molar ratio of catalyst and catalyst structure on the oxidation of styrene were investigated. The oxidation of benzyl halides to their corresponding carbonyl compounds in the presence of this heterogeneous catalyst was studied as well. The catalyst can be recycled several times without significant loss in its activity.

Reactivity and kinetic–mechanistic studies of regioselective reactions of rhodium porphyrins with unactivated olefins in water that form β-hydroxyalkyl complexes and conversion to ketones and epoxides

This article reports on the selective oxidation of unactivated alkenes to ketones and epoxides through the intermediacy of beta-hydroxyalkyl rhodium porphyrin complexes which are formed by reactions of terminal alkenes with tetra(p-sulfonatophenyl)porphyrin rhodium(III) complex. The beta-hydroxyalkyl rhodium porphyrin complexes in water undergo beta-C-H elimination to produce ketones in aqueous pH 9.0 solutions and O-H deprotonation in KOH/DMSO solutions resulting in the rapid and quantitative intramolecular nucleophilic displacement to form 1,2-epoxyalkanes.

Hypervalent iodine-mediated aminobromination of olefins in water

The PhI(OAc) 2-catalyzed aminobromination of electron-deficient olefins has been achieved in pure water with TsNH 2 and NBS as nitrogen and bromine sources, respectively. With a catalytic amount of PhI(OAc) 2, various olefins including α,β-unsaturated ketones, cinnamates, and cinnamides could be aminobrominated efficiently, giving the vicinal bromoamines in good yields and high regio- and diastereoselectivities. Utilizing water as solvent was crucial to realize this aminobromination reaction catalytically. The regioselectivity for the aminobromination of styrenes under the present aqueous conditions was also dramatically improved.

Methanol as a Reaction Medium and Reagent in Substrate Reactions of Rhodium Porphyrins

Methanol solutions of rhodium(III) tetra(p-sulfonatophenyl) porphyrin [(TSPP)Rh(III)] have a hydrogen ion dependent equilibrium between bis-methanol, monomethoxy monomethanol, and bis-methoxy complexes. Reactions of dihydrogen (D(2)) with solutions of [(TSPP)Rh(III)] complexes in methanol produce equilibrium distributions of a rhodium hydride [(TSPP)Rh(III)-D(CD(3)OD)](-4) and rhodium(I) complex [(TSPP)Rh(I)(CD(3)OD)](-5). The rhodium hydride complex in methanol functions as a weak acid with an acid dissociation constant of 1.1(0.1) x 10(-9) at 298 K. Patterns of rhodium hydride substrate reactions in methanol are illustrated by addition with ethene, acetaldehyde, and carbon monoxide to form rhodium alkyl, alpha-hydroxyethyl, and formyl complexes, respectively. The free energy change for the addition reaction of [(TSPP)Rh(III)-D(CD(3)OD)](-4) with CO in methanol to produce a formyl complex (DeltaG(o)(298K) = -4.7(0.1) kcal mol(-1)) is remarkably close to DeltaG(o)(298K) values for analogous reactions in water and benzene. Addition reactions of the rhodium hydride ([(TSPP)Rh(III)-D(CD(3)OD)](-4)) with vinyl olefins invariably yield the anti-Markovnikov product which places the rhodium porphyrin on the less hindered terminal primary carbon center. Addition of the rhodium-methoxide unit in [(TSPP)Rh(III)-OCD(3)(CD(3)OD)](-4) with olefins to form beta-methoxyalkyl complexes places rhodium on the terminal carbon for alkene hydrocarbons and vinyl acetate, but vinyl olefins that have pi-electron withdrawing substituents have a thermodynamic preference for placing rhodium on the interior carbon where negative charge is better accommodated. Equilibrium thermodynamic values for addition of the Rh-OCD(3) unit to olefins in methanol are evaluated and compared with values for Rh-OH addition to olefins in water.

Micellar Effects in Olefin Hydroformylation Catalysed by Neutral, Calix[4]arene‐Diphosphite Rhodium Complexes

AbstractThe combination of calixarene‐derived surfactants and neutral rhodium complexes containing a hemispherical “1,3‐calix‐diphosphite” ligand led to efficient catalysts for the hydroformylation of octene and other olefins in water. While the surfactants allowed the formation of micelles that dissolve both the catalyst and the alkene, thereby resulting in high olefin:rhodium ratios, the diphosphite provided a tight envelope about the catalytic centre able to drive the reaction towards the linear aldehydes. Best results in the hydroformylation of 1‐octene were obtained when using [tetra(p‐sulfonato)]‐(tetra‐n‐butoxy)‐calix[4]arene as surfactant. With this additive remarkable linear to branched aldehyde ratios of up to 62 were obtained, the corresponding activities being higher than those observed when operating in an organic solvent [turnover frequencies (TOFs) up to 630 mol(converted 1‐octene)⋅ mol(Rh)−1⋅h−1].

Enantioselective Friedel–Crafts Reactions in Water Using a DNA‐Based Catalyst

Taking the plunge: The first example of a Lewis acid catalyzed asymmetric Friedel-Crafts alkylation with olefins in water is described. By using loadings of a DNA-based copper catalyst as low as 0.15 mol %, good yields and excellent enantioselectivities were obtained in the reaction of alpha,beta-unsaturated 2-acyl imidazoles with heteroaromatic pi nucleophiles. dmbpy = 4,4'-dimethyl-2,2'-bipyridine.

A simple protocol for the michael addition of indoles with electron deficient olefins catalysed by TBAHS in aqueous media and their broad spectrum antibacterial activity

Tetrabutylammonium hydrogen sulfate catalysed addition of indoles to electron deficient olefins in water generated the corresponding Michael adducts in good to excellent yield. The Michael addition of indole occurred regioselectively at position 3 and the N-alkylated products have not been observed. The synthesized compounds were tested for their antibacterial activity against four microorganisms namely, E. coli NCIM 2931, S. aureus NCIM 5021, P. vulgaris NCIM 2813, P. aeruginosa NCIM 5029 by micro dilution method. These compounds showed MIC (Minimum Inhibitory Concentration) values in the range of 0·16–2·67 µM.

Organocatalytic Michael Addition of Indoles to Activated Alkenes in Water

Reported is a Michael addition of indole derivatives to activated olefins in water, catalyzed by carbohydrate-based tolylsulfonyl hydrazines. The reaction does not proceed in the absence of catalyst and is, as expected, regioselective at the indole 3-position. The authors propose that the tolylsulfonyl hydrazine is the effective catalytic functional group and that the carbohydrate portion acts as a surfactant. Evidence for this claim is given in that the reaction does not proceed when the carbohydrate portion is replaced by a phenyl group, and the reaction is poorly catalyzed by sodium dodecyl sulfonate. Interestingly, this reaction proceeds poorly in organic solvents such as THF or CH2Cl2.

Michael Addition of Indoles to Electron Deficient Olefins in Water Catalyzed by Potassium Bisulfate.

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