Micellar Catalyst Research Articles

An efficient, green and micellar catalyzed preparative-scale synthesis of 3,4-Disubstituted isoxazole-5(4H)-ones in the water

The one-pot three-component synthesis of 3,4-Disubstituted isoxazole-5(4H)-ones has been developed using an aqueous micellar medium as a catalyst under milder reaction conditions. The reaction was completed by using 25 mol% of sodium lauryl sulfate in an aqueous medium at room temperature. The reaction employs a green solvent, an eco-friendly reagent, and a non-chromatographic method for purification. The present reaction tolerates several substituted aldehydes and has proved to be efficient along with excellent yield. Moreover, the micellar catalyst was recovered and reused several times without significantly losing its catalytic activity.

Saponin: a green and efficient natural surfactant for Suzuki–Miyaura cross-couplings of heteroaryl substrates in aqueous media at ambient conditions

Herein, we report a commercially available natural saponin acting as a surfactant and serving as a micellar catalyst, enabling Suzuki–Miyaura cross-coupling effectively with highly challenging heteroaromatic substrates in water at room temperature.

Triton-X-100 as an Organic Catalyst for One-Pot Synthesis of Arylmethyl-H-phosphinic Acids from Red Phosphorus and Arylmethyl Halides in the KOH/H2O/Toluene Multiphase Superbase System

Triton-X-100, a polyethylene glycol 4-(tert-octyl)phenyl ether, has been found to be an active micellar organic catalyst for the one-pot selective synthesis of arylmethyl-H-phosphinic acids in up to 65% yields by the direct phosphinylation of arylmethyl halides with red phosphorus in the KOH/H2O/toluene multiphase superbase system. The catalyst demonstrates a good recyclability. As a result, an expeditious method for the chemoselective synthesis of arylmethyl-H-phosphinic acids—versatile sought-after organophosphorus compounds—has been developed. The synthesis is implemented via direct alkylation/oxidation of red phosphorus with arylmethyl halides, promoted by superbase hydroxide anions using Triton-X-100 (a commercial off-the-shelf organic recyclable micellar catalyst). The reaction comprises the hydroxide anions-assisted disassembly of Pred 3D polymer molecules triggered by the separation from the potassium cation in ordinary crown-like micelles to produce polyphosphide anions in aqueous phase. Further, polyphosphide anions are alkylated with arylmethyl halides in organic phase in the presence of the catalytic Triton-X-100 reverse micelles and alkylated polyphosphide species undergo the double hydroxylation. The advantages of the strategy developed include chemoselectivity, benign and accessible starting reagents, catalyst recyclability, and facile one-pot implementation.

Chemoselective Synthesis of Alkylphosphinic Acids from Red Phosphorus and Alkyl Bromides in the System KOH/H2O/Toluene/Micellar Catalyst

Chemoselective Synthesis of Alkylphosphinic Acids from Red Phosphorus and Alkyl Bromides in the System KOH/H2O/Toluene/Micellar Catalyst

Kinetics of Epoxidation of Cyclooctene with Ionic Liquids Containing Tungstate as Micellar Catalyst

AbstractThe kinetics of cyclooctene epoxidation with H2O2 by micellar catalysis was studied. As catalyst, an ionic liquid (IL) containing the catalytically active tungstate anion was used. The tungstate IL forms micelles in the aqueous H2O2 phase. It is simply formed by dissolving sodium tungstate and 1‐octyl‐3‐methylimidazolium tetrafluoroborate [OMIM][BF4] in aqueous H2O2. For the epoxidation of cyclooctene by micellar catalysis, a power law kinetic model was determined that takes the critical micelle concentration into account. The kinetics of the [OMIM][BF4]/Na2WO4 catalyst is similar to pure [OMIM]2[WO4], which indicates that the active species is formed in situ. Addition of phenylphosphonic acid improves the activity of the tungstate IL. The most effective catalyst was tested in a semi‐continuous and continuous loop reactor.

Synthesis and screening for antioxidant and cytotoxic activities of novel 2-thioxo-benzo[f]chromeno[2,3-d]pyrimidin-4-ones derived by cetylpyridinium chloride catalyzed multicomponent reactions in aqueous micellar media

The cetylpyridinium chloride (CPC) has been used as micellar catalyst in three-component one-pot reaction involving thiobarbituric acids, aromatic aldehydes and β-napthol for synthesizing the novel 2-thioxo-benzo[5,6]chromeno[2,3-d]pyrimidin-4-one derivatives in aqueous media. These 2-thioxo-benzo[5,6]chromeno[2,3-d]pyrimidin-4-one derivatives have been screened for antioxidant and cytotoxic activities. It has been found that 2-thioxo-5-(4-nitrophenyl)-benzo[f]chromeno[2,3-d]pyrimidin-4-one (4a) has shown highest scavenging activity value to reduce DPPH free radicals, which may be due to the presence of nitro group at para-position. Three compounds, 4a, 4b and 4o show significant in vitro antitumor activity. The study of the antioxidant and cytotoxic activities reveal that all the compounds show moderate to good activity indicating that the presence of thiouriedo linkage in the pyrimidine nucleus and the chromeno group attached to pyrimidene moiety are responsible for these activities.

Ru(III) single site solid micellar catalyst for selective aqueous phase hydrogenation of carbonyl groups in biomass-derived compounds

Catalytic processes in water have a lower environmental impact, cost, and toxicity than in organic solvents. Considering the high content of water in biomass, it would be natural to use aqueous phase catalytic technology for the production of valuable products. However, in the aqueous phase, most metal-based catalysts suffer from low activity, low selectivity and deactivation due to metal oxidation and leaching. In this paper, we propose a solid micellar Ru catalyst (Ru(III)@MCM) based on single-site Ru(III) species stabilized by cetyltrimethylammonium (CTA+) surfactant and immobilized in the walls of MCM-41 for the selective aqueous phase hydrogenation of carbonyl groups. This catalyst demonstrates exceptional selectivity, activity, and stability in comparison with conventional metallic catalysts. DFT modeling suggests that the reaction proceeds via heterolytic dissociation of hydrogen, forming a Ru-Hydride species, and subsequent hydride transfer to the carbonyl group. Water plays a key role in avoiding product inhibition.

Highly Efficient Production of Tailored Monascus Pigments by Using a Biocompatible Chemical Reaction Interfacing with Microbial Metabolism

A biocompatible reaction interfacing with microbial metabolism is an efficient approach for production of desired chemicals. Monascus pigments are a traditional natural food colorant from a microbial source. The major color components are red Monascus pigments (RMPs) with various primary amine resides as well as some minor components of yellow ones (YMPs) and orange ones (OMPs). Herein, we elucidate the pathway of OMP degradation involving nucleophilic attack of water on OMPs for the first time. On the basis of OMP degradation and the conversion of OMPs into RMPs sharing a similar reaction mechanism, i.e., nucleophilic attack of water or primary amine on the activated OMPs, we design cascade reactions including biosynthesis of OMPs and biocompatible chemical conversion of OMPs into the stable RMPs with a single glycine residue using a flexible combining chemocatalyst (phosphate ion) and micellar catalyst (Triton X-100). The cascade reactions ensure that OMPs maintain a very low concentration during microbial fermentation by rapid chemical conversion of OMPs into the stable RMPs. In this way, the metabolite profile of microbial fermentation is tailored to RMPs with a single glycine residue as the major color components while free of OMPs and YMPs. Meanwhile, the possible OMP degradation as well as feedback inhibition is eliminated, and a high concentration of RMPs 3.2 mM (1.4 g/L) is also achieved. Designing cascade reactions also has potential for the efficient microbial fermentation of other azaphilone alkaloids.

One-pot Pseudo-Domino Three-Component Knoevenagel Condensation Reaction in Water Enabled by Micellar Catalyst: Mechanism and Reactivity

The micellar catalysis is well-known for its hydrophobic effect that is the tendency of nonpolar groups to cluster within the lipophilic core so as to shield them from contact with an aqueous environment formed upon the dissolution of a surfactant in water. This provides a unique opportunity to establish organic transformations in greener solvents, such as water leading to organic waste control and easy product isolation protocols. Considering the significant interaction of thiobarbituric acid moieties in a biological macromolecule core, herein, a highly efficient procedure for the synthesis of biological and medicinal important 5-(arylmethylene)dihydro-2-thioxo-4,6(1H,5H)-pyrimidinediones via Knoevenagel condensation of thiobarbituric acids and aldehydes catalyzed by a surfactant, sodium dodecyl sulfate, is developed. The synthetic procedure shows the excellent activity of the micellar catalysts towards the aldehyde activation leading to a facile condensation. The application of the method is demonstrated by further synthesis of 5,5'-(4-arylmethylene)bis[dihydro-2-thioxo-4,6(1H,5H)- pyrimidinediones]. Theoretical studies of the reaction were also carried out to investigate the effect of electron releasing and electron-withdrawing group in benzaldehyde on the reaction.

Thermo‐responsive block copolymer micelle‐supported (S)‐α,α‐diphenylprolinol trimethylsilyl ether for asymmetric Michael addition of nitroalkenes and aldehydes in water

AbstractAn amphiphilic block copolymer PNIPAM53‐b‐(PS30‐co‐P4AMS10) was facilely prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization. The immobilization of (S)‐α,α‐diphenylprolinol trimethylsilyl ether onto the block copolymers was then performed through using copper‐catalyzed alkyne‐azide cycloaddition (CuAAC), and the generating amphiphilic diblock copolymer supported chiral catalyst PNIPAM53‐b‐(PS30‐co‐P4AMS10)/proTMS was self‐assembled into micelles with regular diameters about 50 nm in aqueous solution. The micellar catalyst was further used for the asymmetric Michael reaction between propanal and trans‐β‐nitrostyrene in water. Using only 1 mol% micellar catalyst, the corresponding Michael addition products could be obtained in good yields and high enantioselectivities as well as good diastereoselectivities. In addition, this micellar catalyst could be reused at least for four times. Moreover, the micellar catalyst could be applied for the asymmetric addition reaction of 4‐chlorocinnamyl aldehyde and nitromethane, and thus constructing the baclofen pharmaceutical intermediate.

Transfer-hydrogenation reactions of ketones/aldehydes in water using first generation ruthenium indenylidene olefin metathesis catalyst: One step towards sequential cross-metathesis/transfer hydrogenation reactions

The transfer hydrogenation reactions of various ketones/aldehydes and one-pot cross-metathesis/transfer hydrogenation (CM/TH) reactions of 10-undecenal were carried out in water media using first generation ruthenium-indenylidene complex (M1). A stable emulsion with an average particle size of 23.00 (±7.20) nm was formed in water media using non-ionic (Tween 20) and cationic (dodecyltrimethylammonium chloride) surfactants in the presence of acetophenone, M1 (1%) and sodium formate, yielding corresponding alcohol derivatives in quantitative yields.The performance of M1 (5%) was tested on sequential cross-metathesis/transfer hydrogenation reaction of 10-undecenal using methyl acrylate as the cross-metathesis partner in water. The sequential CM/TH reaction of 10-undecenal was found to proceed even in tap water under air atmosphere using micellar catalyst system, giving the corresponding CM/TH product in 65% yield.

Micellar catalysed and heteroaromatic base promoted rate enhancement of oxidation of an alicyclic alcohol in aqueous medium

Under pseudo 1st order reaction condition cyclohexanol, an alicyclic alcohol produces cyclohexanone with a moderate rate of oxidation. Promoters and surfactants enhanced the rate of oxidation with chromic acid. The product is confirmed by melting point study; 2, 4 DNP test; IR and NMR study. Among the three micellar catalyst SDS shows higher rate where as phen promoted reaction shows smaller half life. Combination of SDS and bpy shows a 600 fold enhancement in the rate of the reaction. NMR study is also carried out to confirm the interaction between the surfactants and cyclohexanol.

Kinetic Model of Two‐Phase Epoxidation with Ionic Liquids as Micellar Catalysts

AbstractThe biphasic catalytic epoxidation of cyclooctene using the ionic liquid (IL) 1,2‐dimethyl‐3‐octyl‐imidazolium perrhenate ([OMMIM]ReO4) as micellar catalyst and H2O2 as oxidant was investigated. Kinetic experiments were carried out in the intrinsic kinetic regime as proved by variation of stirring rate and temperature. Variation of catalyst concentration allowed for determination of the critical micellar concentration (CMC) of the catalytic IL. The effect of substrate concentrations on the reaction rate was also assessed. Based on the experiments, a kinetic model adapted from enzyme catalysis was proposed to account for the micellar reaction environment. The model takes into account the onset of micelle formation at the CMC. The application of the kinetic model illustrated the good agreement with the experimental data. The model will be applied to other micellar epoxidation reactions and for the design of an appropriate reaction setup in the future.

Water-soluble palladium nanoparticles as an active catalyst for highly selective hydrogenation of nitrobenzene to aniline

Palladium (Pd) nanoparticles (NPs) stabilized by tri-block copolymer polyoxyethylene–polyoxypropylene–polyoxyethylene (P123) micelles were synthesized in water using a hydrogenation reduction method. Well-dispersed P123 micelles in the aqueous phase favored the stabilization of Pd NPs. The P123–Pd micellar catalyst was first applied in the liquid phase hydrogenation of nitrobenzene (NB), showing excellent catalytic activity, and the only reaction product detected was aniline (AN). Using water as the reaction medium and under mild conditions, both the preparation of catalysts and NB hydrogenation were convenient and environmentally friendly. Under the optimal conditions, the isolated catalyst phase could be recycled at least five times, and the catalytic activity and selectivity remained unchanged. A reaction scheme was suggested. First-order kinetics was determined at 3.0 MPa hydrogen pressure and temperature 30–75 °C, and the activation energy was 40.18 kJ mol−1. This work provides an environmentally benign and effective method for the hydrogenation of NB to AN.

Micellar effect on hetero-aromatic nitrogen base promoted chromic acid oxidation of 1.3-propanediol in aqueous media at room temperature

Surfactants are classified on the basis of the nature of the hydrophilic groups. Surfactant micelle represents a tiny template or nanoreactor which is generally used for preparing nano-structured materials of desired sizes and shapes with required functionalities. In this present investigation chromic acid oxidation of 1.3-propanediol (1.3-PDO) to 3-hydroxy propionaldehyde (3-HPA) was carried out by using four representative promoters: picolinic acid (PA), 2.3-pyridine dicarboxylic acid (2.3 diPA), 2.2′-bipyridine (bipy) and 1.10-phenanthroline (phen) in presence and absence of surfactants sodium dodecylsulphate (SDS), N-cetylpyridinium chloride (CPC) and Triton-X-100 (TX-100). Reactions were performed under pseudo-first-order condition: [1.3-PDO]T≫[Cr(VI)]T in aqueous media at 30°C temperature. Different combinations were performed to select the suitable combination of promoter and micellar catalyst for this oxidation. Based on the kinetic results, combination of TX-100 and phen was found to be the most suitable one for this oxidation. The mechanisms of both unpromoted and promoted reaction paths were proposed. The product was confirmed by 2.4-DNP test followed by FTIR spectroscopy of the hydrazone derivative.

Picolinic Acid Promoted Permanganate Oxidation of D-Mannitol in Micellar Medium

AbstractKinetics of permanganate oxidation of D-mannitol have been investigated spectrophotometrically under pseudo-first-order conditions in aqueous acidic media at 30 °C. The spectral analysis of hydrazone derivative of the product indicates the product to be an aldehyde. The observed rate constant value was found to be relatively slow in the uncatalyzed path, which increases by the presence of four isomeric promoters: 2-picolinic acid (2-PA), 4-picolinic acid (4-PA), 2,3-dipicolinic acid (2,3-diPA) and 2,6-dipicolinic acid (2,6-diPA). The catalytic effect of sodium dodecylbenzene sulfonate (SDBS) surfactant on the permanganate oxidation of D-mannitol has been also studied in the presence of the promoters. The critical micelle concentration (CMC) of SDBS alone and in presence of D-mannitol was determined by conductometry and spectrophotometry. The aggregation and morphological changes during reaction were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The variation of the reaction rates for the different promoters in the presence and absence of SDBS micellar catalyst is discussed qualitatively in the terms of partitioning nature of substrate, charge of surfactant and reactants. 2,3-diPA in association with SDBS as micellar catalyst accelerated the reaction velocity compared to the uncatalyzed path.

Micellar Catalysis: Bioinspired Micellar Copper Protoporphyrin as a High Performing Nano-Catalyst.

Herein we have engineered a micellar Cu protoporphyrin catalyst that mediates carbon bond activation using peroxide as an electron source. Cu protoporphyrin is a biomimetic model of active site of chloroperoxidase enzyme, which catalyzes the carbon bond halogenation in the presence of a suitable amount of H2O2. The encapsulation of Cu(II) Protoporphyrin IX/L-Cysteine inside of cetyltrimethylammonium bromide micelle increases the rate of chlorination at pH 3. The cited catalyst resists high concentrations of hydrogen peroxide, which is previously reported as a suicide inactivator component of hemo-enzymes. Isothermal Titration Calorimetry (ITC) and Dynamic Light Scattering (DLS) data have revealed the formation of a micellar complex by encapsulation of six Cu(II) proporphyrins within each micelle. Moreover, electrochemical investigations indicate that L-Cysteine increases the intensity of electron transferred due to the formation of self-assembled monolayer on Au electrode. Our results paved a road toward the design of a more robust mimetic catalysis based on Protoporphyrin IX derivatives.

Highly Selective Hydrogenation of α-Pinene Catalyzed by Ru Nanoparticles in Aqueous Micellar Microreactors

Ru nanoparticles were prepared using polyoxyethylene–polyoxypropylene–polyoxyethylene triblock copolymer (F127, Mw: 13,000) micelles as stabilizers. The F127-Ru micellar catalyst was used in the hydrogenation of α-pinene to cis-pinane. Under very mild conditions, the conversion of α-pinene was 99.9 %, and selectivity for cis-pinane reached 99.0 %. The isolated catalyst phase could be reused six times with almost unchanged catalytic activity and selectivity. The improvement in conversion and selectivity was attributed to the formation of micellar microreactors, with the water insoluble substrate solubilized in the hydrophobic core of the micelles. This method offers an effective pathway for the production of a high value-added product from turpentine, and provides a reference for the catalytic hydrogenation of other hydrophobic natural products.

Combination of Best Promoter and Micellar Catalyst for Chromic Acid Oxidation of D-Arabinose in Aqueous Media at Room Temperature

AbstractThe present paper describes the kinetics and mechanism for oxidation of D-arabinose by Cr(VI) in the presence of a micellar media. The anionic surfactant sodium dodecyl sulphate (SDS) and nonionic surfactant Triton-X-100 (TX-100) accelerate the process while the cationic surfactant N-cetylpyridinium chloride (CPC) retards the reaction. A suitable mechanism has been proposed. The reaction constants involved in different steps of the mechanism have been calculated. Formic acid and erythronic acid were reported as the products of oxidation of the sugar.

Best Combination of Promoter and Micellar Catalyst for Room Temperature Rapid Conversion of D-Lyxose to D-Lyxonic Acid in Aqueous Medium

AbstractThe kinetic study of catalytic oxidation of D-lyxose by hexavalent chromium has been investigated spectrophotometrically under pseudo first order condition at temperature 313 K. The rate of oxidation of D-lyxose is very slow. Picolinic acid (PA), 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen) are used as promoter to accelerate the rate of the reaction. Phen acts as the most effective promoter in aqueous medium. The rate of the reaction is also increased in presence of nonionic surfactant Triton-X-100 (TX-100) and anionic surfactant sodium dodecyl sulphate (SDS). They are used as catalyst in this reaction. Thus the observed micellar effects have been explained by considering the hydrophobic and electrostatic interactions between the reactants and surfactants in terms of the proposed mechanism. However, the combination of promoter and surfactants produces a better result. The maximum rate enhancement is obtained in presence of the combination of phen and TX-100.