Indium(III) chloride-catalyzed oxidative cleavage of carbon-carbon multiple bonds by tert-butyl hydroperoxide in water—a safer alternative to ozonolysis

An efficient and general method for the oxidative cleavage of alkenes and alkynes using tert-butyl hydroperoxide and indium(III) chloride as catalyst in water to give the corresponding carboxylic acids or ketones has been achieved. The reaction conditions are compatible with sensitive moieties such as peptide bonds, tert-butyl carboxylic esters and N-Boc-protected tryptophan. The catalyst could be recycled.     

A novel amino acid functionalized ionic liquid promoted one-pot solvent-free synthesis of 3,4-dihydropyrimidin-2-(1H)-thiones

An environmentally benign, cheap and reusable L-amino acid functionalized ionic liquid [L-AAIL]/AlCl₃ was found to be an effective catalyst for the synthesis of 3,4-dihydropyrimidine-2-(1H)-thione derivatives in good to excellent yield under solvent-free condition. Compared with the classical Biginelli reactions, this method consistently enjoys the advantages of mild reaction conditions, easy work-up, and short reaction time. These one-pot three-component Biginelli products could be separated easily from the catalyst–water system, and the catalyst could be reused at least five times without noticeably reducing catalytic activity.     

Poly(basic ionic liquid) coated magnetic nanoparticles: High-loaded supported basic ionic liquid catalyst

A novel poly(ionic liquid) (PIL) coated magnetic nanoparticle was synthesized by distillation-precipitation-polymerization of 1-vinyl-3- ethyl imidazolium in the presence of surface modified magnetic nanoparticles. The resulting catalyst was used as magnetic heterogeneous base catalyst for the synthesis of 4H-benzo[b]pyrans in water. The separation of the catalyst from the reaction mixture was readily achieved by simple magnetic decantation and the catalyst could be easily recycled without appreciable loss of catalytic activity. Because of polymer layers coated the surface of the magnetic nanoparticles, the catalyst has a high loading level of ionic liquid.     

Chitosan-g-mPEG-supported palladium (0) catalyst for Suzuki cross-coupling reaction in water

A chitosan-g-mTEG (methoxy triethylene glycol)- or mPEG (methoxy polyethylene glycol)-supported palladium (0) catalyst was prepared for the Suzuki cross-coupling reaction in water. The catalyst showed excellent catalytic activity in the Suzuki cross-coupling reaction without additional phase transfer reagents due to the enhanced solubility of the organic substrate by PEG grafting. In addition, the catalyst could be reused up to five times with the catalytic activity being recovered easily after simple manipulations.     

Facile synthesis of S-arylisothioureas via the S-arylation of arylthioureas with aryl iodides in water

An environmentally benign, simple and highly efficient protocol for the synthesis of S-arylisothiourea derivatives has been achieved in good to excellent yields by reacting a series of aryl iodides with arylthioureas, using inexpensive CuSO₄·5H₂O as catalyst in water without PTC (phase transfer catalyst). The protocol features easy performance, good to excellent yields, good tolerance towards a variety of functional groups, which could be useful for the preparation of some biologically active compounds.     

Selective synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles in water at ambient temperature

A highly selective synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles from the reaction of o-phenylenediamines and aromatic aldehydes in the presence of silica sulfuric acid is reported. The reactions were performed in ethanol or water and the catalyst could be reused for several runs.     

A practical process to chiral ferrocenyl alcohols via asymmetric transfer hydrogenation catalyzed with a PEG-bound Ru catalyst in water and its application in preparing Ugi’s amine

Chiral ligand (S,S)-PEG-BsDPEN has been found to be efficient for the asymmetric transfer hydrogenation of various ferrocenyl ketones. With sodium formate as a hydrogen donor, PEG 2000 and water as the reacting media, the catalyst system could be recycled several times. This procedure could be scaled up to a 100 mmol or more in a common round flask which is easy to perform in ordinary laboratories. The preparation of Ugi’s amine with the ferrocenyl alcohol was also investigated.     

pH-Regulated transfer hydrogenation of quinoxalines with a Cp*Ir-diamine catalyst in aqueous media

The combination of [Cp*IrCl₂]₂ with N-(2-aminoethyl)-4-(trifluoromethyl)benzenesulfonamide constitutes an efficient catalyst for selective transfer hydrogenation of a variety of quinoxalines in water with HCOONa as the hydrogen source, affording the corresponding tetrahydroquinoxalines in good to excellent yields. The catalyst is air-stable, and the reduction could be performed without nitrogen protection. The aqueous phase reduction is shown to be highly pH-dependent, with acidic pH leading to better results. There exits a pH window for optimum rate, and the use of HOAc/NaOAc buffer solution is essential for maintaining a stable pH during the reaction.     

Selective C-C bonds formation,N-alkylation and benzo[d]imidazoles synthesis by a recyclable zinc composite

Earth abundant metals are much less expensive, promising, valuable metals and could be served as catalysts for the borrowing hydrogen reaction, dehydrogenation and heterocycles synthesis, instead of noble metals. The uniformly dispersed zinc composites were designed, synthesized and carefully characterized by means of XPS, EDS, TEM and XRD. The resulting zinc composite showed good catalytic activity for the N-alkylation of amines with amines, ketones with alcohols in water under base-free conditions, while unsaturated carbonyl compounds could also be synthesized by tuning the reaction conditions. Importantly, it was the first time to realize the synthesis of 2-aryl-1H-benzo[d]imidazole derivatives by using this zinc composite under green conditions. Meanwhile, this zinc catalyst could be easily recovered and reused for at least five times.     

Bismuth trichloride-catalyzed oxy-Michael addition of water and alcohol to α,β-unsaturated ketones

An efficient method was developed for the conjugate addition of water to various α,β-unsaturated ketones by using bismuth(III) chloride as a catalyst. The reactions proceeded smoothly in the presence of a catalytic amount of BiCl₃ (20 mol%) in aqueous media to furnish a variety of synthetically useful β-hydroxyl ketones in moderate to good yields. Apart from water molecule, various alcohols could also be employed as nucleophiles to react with α,β-unsaturated ketones, leading to β-alkoxyl ketones in modest to high yields. In addition, the mild reaction conditions also entailed the conjugate addition reactions to proceed with the tolerance to a range of functional groups.     

PEG-modified N-heterocyclic carbene ligands for highly efficient and recyclable Pd-catalyzed Heck reaction in water

A water-soluble and air-stable Pd(OAc)₂/mPEG _n MeImI system was found to be a highly efficient and reusable catalyst for the coupling of aryl halides and styrene in neat water using K₂CO₃ as base. After extraction, the catalytic system could be reused several times with only a slight decrease in its activity.     

In situ prepared CuI nanoparticles on modified poly(styrene-co-maleic anhydride): an efficient and recyclable catalyst for the azide–alkyne click reaction in water

A facile, high-yielding and straightforward methodology for the copper-catalyzed synthesis of 1,4-disubstituted 1,2,3-triazoles in water, using in situ prepared copper nanoparticles (NPs) on modified poly(styrene-co-maleic anhydride) [SMA] catalyst, is reported. The polymer support was easily prepared from the reaction of SMA with 4-aminopyridine and subsequently underwent reaction with CuI NPs. The catalyst was applied for the preparation of triazoles under air, followed by chromatographic separation of the products. The polymer-supported catalyst not only showed high catalytic activity but also showed high 1,4-regioselectivity for the [3 + 2] Huisgen cycloaddition in water as solvent. The products were obtained in good to excellent yields in all cases. The catalyst can be used without pre-activation and reloaded for at least five runs without significant decrease in its activity. The catalyst was characterized by SEM, energy dispersive spectroscopy analysis of X-rays, and inductively coupled plasma.     

Numerical simulation of a new water management for PEM fuel cell using magnet particles deposited in the cathode side catalyst layer

Cathode flooding caused by excessive liquid water is generally recognized as the primary reason for poor cell performance. Recently, when some magnet particles are deposited in the catalyst layer of a cathode and magnetized, the cell performance has been improved compared with that of non-magnetized case. Numerical simulation to explain this phenomenon shows (1) the repulsive Kelvin force caused by the magnet particles manages the liquid water flow in the porous electrode layer; (2) the saturation level of liquid water (s) near the catalyst interface decreases with increasing the residual magnetic flux density of the magnet particle (B_r); (3) the magnet particles improves the fuel cell performance by decreasing the value of s and making more pore space for oxygen gas, and the cell performance of a proton-exchange-membrane (PEM) fuel is improved in the current limited region.     

新型功能离子液体水相催化芳醛与5,5-二甲基-1,3-环己二酮的反应

以N,N,N′,N′-四甲基乙二胺、1,3-丙磺酸内酯为原料,经酸化合成了功能化离子液体N,N,N′,N′-四甲基N,N′-二磺丙基二硫酸氢盐(TSIL)。 TSIL离子液体兼具Bronsted 酸性官能团和季铵盐相转移催化剂的结构,能够实现水相中芳醛与5,5-二甲基-1,3-环己二酮反应,得到氢化氧杂蒽衍生物。 结果表明,合成的TSIL具有较高的催化活性,在水相中于100 ℃下回流2～3 h即可完成反应,产率可达80%～93%。 反应生成的取代氢化氧杂蒽与离子液体的水溶液不相溶,通过简单的过滤可实现产物与催化体系的分离,简化了分离过程,方法操作简便、环境友好、催化剂可回收并重复使用。     

Enantioselective aza-Friedel–Crafts reaction catalyzed by a water inclusion complex of O,O′-diacyl tartaric acid

The efficiency of an O,O′-diacyl tartaric acid derivative as a chiral Brønsted acid catalyst was investigated in the enantioselective Friedel–Crafts reaction of indoles with an α-imino ester. The inclusion of water in the O,O′-di-p-toluoyl-d-tartaric acid catalyst is crucial for obtaining the enantioselectivity, and under optimal conditions the corresponding Friedel–Crafts product was obtained with an enantioselectivity of up to 88% ee.     

Green synthesis of imidazo[1,2-a]pyridines using calix[6]arene-SO3H surfactant in water

In this research, green synthesis of imidazo[1,2-a]pyridines in the presence of calix[n]arenes-SO₃H as a Brønsted acid catalyst and surfactant is described. Using of calix[n]arenes in water provided a hydrophobic cavity that successfully carried out the synthesis reactions at short times with high yields. This catalyst system is recoverable with a simple extraction using an organic solvent and reusable for at least for 5 cycles without any losses of its activity.     

First example of asymmetric transfer hydrogenation in water induced by a chiral amino alcohol hydrochloride

The low-cost and commercially available (−)-ephedrine hydrochloride was firstly employed in the [RuCl₂(p-cymene)]₂-catalyzed asymmetric transfer hydrogenation of prochiral ketones in water. The reaction could be performed in the open air at rt, affording excellent yields (up to 99%) and good enantioselectivities (up to 83% ee). It provided a further step toward the discovery of simplified catalyst systems for eventual availability.     

Catalytic oxidation of primary aromatic amines with sodium periodate catalyzed by Mn(III)salophen complex supported on polystyrene-bound imidazole

The catalytic activity of Mn(III)salophen complex supported on polystyrene-bound imidazole, [Mn(salophen)Cl-PSI], was studied in the oxidation of primary aromatic amines in acetonitrile/water, using sodium periodate as an oxygen source. Amines were oxidized efficiently to their corresponding azo derivatives in the presence of this catalyst. The heterogeneous catalyst showed high stability and reusability in the oxidation reactions and could be reused several times without loss of its activity. The effect of different solvents was studied in the oxidation of p-toluidine and CH₃CN/H₂O was chosen as the solvent.     

A pH-responsive TiO2-based Pickering emulsion system for in situ catalyst recycling

Through tuning the surface wettability of interfacially active TiO₂ particles, a pH-responsive Pickering emulsion system is formed, as in situ separation and recycling of the nano-catalysts system.     

Study on a novel manufacturing process of membrane electrode assemblies for solid polymer electrolyte water electrolysis

A novel manufacturing process for catalyst coated membrane (CCM) was utilized to fabricate the membrane electrode assemblies (MEA) for solid polymer electrolyte (SPE) water electrolysis. The properties and performance of the modified CCM were analyzed and evaluated by SEM, electrochemistry impedance spectroscopy (EIS) and I–V curves. The characterizations reveal that the sprayed Nafion layers are very effective for increasing the reaction interface between SPE and the electrode catalyst layer. The test experiments show that the SPE water electrolyzer with new MEA structure can lower about 0.1 V of water electrolysis voltage at atmosphere pressure and 2 A cm⁻².