An efficient method for the synthesis of 2-aminothiazoles using silica chloride as a heterogeneous catalyst

This article describes a facile and efficient synthesis of 2-aminothiazoles under mild reaction conditions with quantitative yields using silica chloride as an effective heterogeneous catalyst.     

Amidation of alcohols with nitriles under solvent-free conditions using molecular iodine as a catalyst

The reactions of alcohols with nitriles under solvent-free conditions, using molecular iodine as a catalyst, were investigated. The reaction of 1-phenylethanol with propanenitrile produced the amide N-(1-phenylethyl)propanamide, by dehydration and tautomerization, in 71% yield, under the following conditions: temperature=90°C, alcohol:iodine molar ratio=1:0.2, alcohol:nitrile molar ratio=1:5, and reaction time=5 h. The amidation reactivity depended on the stability of the cationic intermediate formed from the alcohol. The reaction of (-)-borneol with benzonitrile produced a racemic amide in 83% yield.     

One-pot synthesis of 1,3-thiazolidin-4-one using ammonium persulfate as catalyst

Ammonium persulfate can be used as a homogeneous catalyst for three-component one-pot synthesis of some 1,3-thiazolidin-4-one derivatives from aldehydes, amines and mercaptoacetic acid under solvent-free conditions with good yields. The characterization of products was generally achieved by IR and NMR techniques. Inexpensive catalyst, high yields, simple product isolation and high atom economy are the noteworthy aspects of the protocols.     

Microwave-assisted one-pot three-component synthesis of thiazolidinones using KSF@Ni as an efficient heterogeneous catalyst

Convenient, one-pot three-component reaction for the synthesis of thiazolidinones from aldehydes, thiosemicarbazide, and maleic anhydride in the presence of KSF@Ni as heterogeneous catalyst under microwave irradiation was developed. Products were obtained in reasonable yield in short reaction time.     

Highly efficient procedure for the synthesis of biodiesel from soybean oil using chloroaluminate ionic liquid as catalyst

The novel efficient procedure has been developed for the synthesis of biodiesel. The chloroaluminate ionic liquid has been selected for the synthesis of biodiesel. The catalyst was very efficient for the reaction with the yield of 98.5% when the reaction was carried out under the conditions of [Et₃NH]Cl-AlCl₃ (x(AlCl₃) = 0.7), soybean oil 5 g, methanol 2.33 g, 9 h, 70 °C. Operational simplicity, low cost of the catalyst used, high yields, no saponification and reusability are the key features of this methodology.     

Functionalized UiO-66 as an efficient catalyst for the synthesis of bio-based poly(1,3-propylene sebacate)

Organometallic catalysts such as titanium-based ones are often used for the melt polycondensation to obtain polyesters. However, they are prone to hydrolysis and may discolor, which may have adverse effects on the molecular weight of the resulting polyesters and their applications. This work aims to use functionalized UiO-66 catalysts for the melt polycondensation of polyesters composed of 1,3-propanediol and 1,10-decanedioic acid ether. The melt polycondensation proceeds in two steps: esterification and polycondensation. A catalytic mechanism is proposed. Compared with tetrabutyl titanate, a classical catalyst, the functionalized UiO-66 ones are more water resistant, less toxic to, and do not discolor. It yields poly(1,3-propylene sebacate) with higher molecular weights. Thus, they are efficient and greener catalysts.     

An efficient oxidation of cyclohexane over Au@TiO2/MCM-41 catalyst prepared by photocatalytic reduction method using molecular oxygen as oxidant

Cyclohexane oxidation using molecular oxygen as oxidant is one of the most challenge subjects. A novel photocatalytic reduction method to prepare Gold nanoparticles Au@TiO₂/MCM-41 was proposed. The prepared samples were characterized by XRD, N₂ adsorption isotherm, FT-IR, TEM and EDS. The results showed that gold nanoparticles were well-dispersed on TiO₂/MCM-41, and TiO₂ was dispersed on the surface of the support and the gold existed as Au⁰. Newly-developed catalyst was promising for the cyclohexane oxidation, achieving a turnover frequency (TOF) as high as 29,145 h^− 1 with 9.87% conversion of cyclohexane.     

Catalytic oxidation of 1,3-diisopropylbenzene using imidazolium ionic liquid as catalyst

Peroxidation of alkylaromatics is the key step in the synthesis of phenols. Different imidazolium ionic liquids were investigated for the oxidation of cumene. The selectivity of cumene hydroperoxide (CHP) increased with different ionic liquids in the order [C₄mim]Cl<[C₄mim]Br<[C₄mim]BF₄<[C₄mim]OH. This finding could be interpreted as being due to the partial decomposition of CHP by the acidic proton of the imidazolium cation. Thus [C₄mim]OH was chosen as the catalyst for the oxidation of 1,3-diisopropylbenzene to corresponding hydroperoxides and its derivatives. The catalytic performance of [C₄mim]OH was also better than that of the traditional catalyst NaOH. Furthermore, the effects of the operating variables were investigated and the mechanism was discussed.     

Supported imidazole as heterogeneous catalyst for the synthesis of cyclic carbonates from epoxides and CO2

Imidazole anchored onto a silica matrix, by means of a propyl linkage, is found to be an effective heterogeneous catalyst for the synthesis of cyclic carbonates from epoxides and CO₂ in near quantitative yield. The versatility of this catalyst is demonstrated by using different substrates (epichlorohydrin, propylene oxide, butylene oxide and styrene oxide) for this cycloaddition reaction. These CO₂ insertion reactions were typically carried out in the temperature range of 343 to 403 K at 0.6 MPa CO₂ pressure under solvent-free conditions. Several spectroscopic methods were used to characterize the catalyst and study the integrity of the fresh and spent catalysts.     

Anionic ring-opening polymerization of five-membered cyclic carbonates derived from aldohexopyranosides

Polymer Bulletin - To investigate the relationship between the steric structures and polymerizability of five-membered cyclic carbonates, the anionic ring-opening polymerizations of methyl...     

An efficient synthesis of 1,8-dioxo-octahydroxanthenes using heterogeneous catalysts

1,8-Dioxo-octahydroxanthenes have efficiently been synthesized from 5,5-dimethyl-1,3-cyclohexanedione and aromatic aldehydes using silica supported sodium hydrogen sulfate (NaHSO₄ · SiO₂) or silica chloride as a heterogeneous catalyst. The experimental procedure is very simple and the products are formed in high yields.     

杂多酸催化剂走向分子设计

从分子设计的角度讨论了杂多酸的结构与催化性能、制备方法以及在有机合成、石油化工中的应用进展。     

Diphenylmethane synthesis using ionic liquids as lewis acid catalyst

Friedel-Crafts alkylation of benzene with benzyl chloride was studied by using organochloroaluminate ionic liquids as Lewis acid catalyst. The reaction was performed in the temperature range of 40 to 70 oC at benzene/ benzyl chloride=17, where selectivity to diphenylmethane was high. The optimum AlCl3/BMIC ratio of the ionic liquid for the benzylation reaction was 2. Superior performance was obtained with butyl group constituting the cationic species of the ionic liquid. Stirring speed had a major impact on catalytic activity of the BMIC-AlCl3 ionic liquid; benzyl chloride conversion decreased substantially from 98 to 68% as stirring speed was reduced from 900 to 500 rpm, and eventually no reaction took place at 200 rpm. BMIC-AlCl3 ionic liquid was more active than Fe-MCM-41 at the expense of a small drop in selectivity but still higher than 96% selectivity was obtained. The ionic liquid could be easily recovered after phase separation. The performance of BMIC-AlCl₃ ionic liquid was maintained after the second run with 97.4% conversion and 95.6% selectivity, but a sudden drop in activity was observed after the third run with only 26.8% conversion.     

An efficient self-assembly Ru-Al material as heterogeneous catalyst for water oxidation

A self-assembly ruthenium material connected by Al^3 + ions (Ru-Al) was synthesized and used to catalyze water oxidation. This Ru-Al material displayed much better performance than its precursor and the free precursor mixed with Al^3 + ion on both efficiency and stability during the catalytic water oxidation period. Based on the catalytic metal center, a turnover number (TON) of more than 2100 was achieved.     

Polyethylene glycol as an efficient and reusable solvent medium for the synthesis of thiohydantoins using K2CO3 as catalyst

Polyethylene glycol was found to be an inexpensive, non-toxic, recyclable and an effective medium for the synthesis of thiohydantoin derivatives in the presence of K₂CO₃ as the catalyst. The procedure is operationally simple and environmentally benign.     

ZnBr2–Ph4PI as highly efficient catalyst for cyclic carbonates synthesis from terminal epoxides and carbon dioxide

The catalyst systems composed of ZnBr₂ and different phosphonium salts were examined for solvent-free synthesis of cyclic carbonates from CO₂ and terminal epoxides under mild conditions. Among the catalysts investigated, ZnBr₂–Ph₄PI was found to be the best while those of ZnBr₂–phosphine oxide (Bu₃PO or Ph₃PO) show no catalytic effect. It is apparent that the halide ions of phosphonium salts have an essential role to play in the reaction. The catalytic activity of ZnBr₂–Ph₄PI increases with a rise of Ph₄PI to ZnBr₂ molar ratio up to 6, above which there is little change in catalytic activity. We observed that with a rise in ZnBr₂ to Ph₄PI molar ratio, there is increase in epoxide conversion but decline in TOF_PO (estimated based on the site number of Zn²⁺). The effect of water on the reaction was investigated for the first time. We found that the presence of even a trace amount of water would result in a marked decline in reactivity, and the observation provides a valid explanation for why reproducibility of results is poor among researchers so far. The influences of other parameters such as reaction temperature and CO₂ pressure on the catalytic performance of ZnBr₂–PPh₄I were also studied. It is shown that the catalyst is sensitive to reaction temperature, and a rise of reaction temperature up to 130 °C favors the formation of cyclic carbonates. We observed that activity increases with rise in CO₂ pressure and reaches a maximum at an initial CO₂ pressure of 2.5 MPa. Moreover, a plausible reaction mechanism has been proposed.     

羟基磷灰石多相催化合成对硝基苯甲醛的研究

经Ru(Ⅲ)交换的羟基磷灰石(RuHAP)作多相催化剂,用氧气常压氧化对硝基苯甲醇制备了对硝基苯甲醛。研究了催化剂用量、催化剂中Ru的质量分数、反应温度、反应时间等因素对对硝基苯甲醛产率的影响。反应在优化条件下：催化剂中Ru的质量分数为15％,催化剂用量质量分数占对硝基苯甲醇的5％,甲苯为溶剂,反应温度80℃,反应时间3h,对硝基苯甲醛的产率达97．3%。此催化剂重复使用3次,对硝基苯甲醛的产率未见明显降低。     

Porous modified bentonite as efficient and selective catalyst in the synthesis of 1,5-benzodiazepines

The synthesis of 1,5 benzodiazepine using natural and modified Argentinean bentonite (pillared layered clay and porous clay heterostructure) as catalysts through a condensation reaction between o-phenylenediamine (o-PDA) and excess of acetone as reactive and solvent at room temperature is reported. The catalysts were found to be highly active and selective, affording a high yield of the corresponding benzodiazepine. The effects of the modification of the natural bentonite and reaction conditions, such as temperature, time and amount of catalyst were investigated. The catalysts were also successfully employed for the preparation of other derivatives of 1,5-benzodiazepine using substituted o-PDAs and ketones. In all cases, the reactions are highly selective and are completed within 1–3 h. The catalyst showed excellent activity in all cases, showing 86–90% isolated yields of the corresponding derivatives of 1,5-benzodiazepine. The easy work-up procedure and the recyclable catalyst make this methodology attractive for large-scale operations.     

A highly stable and efficient catalyst for direct synthesis of LPG from syngas

Liquefied petroleum gas (LPG) fuel was directly synthesized from syngas over a hybrid catalyst which contained a methanol synthesis catalyst and zeolite. The new hybrid catalyst composed of (Pd–Ca/SiO₂) and β-zeolite, showed a high activity and selectivity for LPG production. X-ray diffraction (XRD) characterization of the catalyst was used to analyze the deactivation of (Pd–Ca/SiO₂)/β-zeolite.