An efficient method for synthesis of acylals from aldehydes using multi-walled carbon nanotubes functionalized with phosphonic acid(MWCNTs-C-PO_3H_2)

MWCNTs-C-PO_3H_2 has been used as an efficient,heterogeneous and reusable nanocatalyst for synthesis of acylals from aldehydes under solvent-free conditions at room temperature.A wide range of aldehydes was studied and corresponding products were obtained in good to excellent yields in short reaction times.Nanocatalyst can be easily recovered by centrifuge and reused for subsequent reactions for at least five times without deterioration in catalytic activity.The major advantages of the present method are high yields,short reaction time,recyclable catalyst and solvent-free reaction conditions at room temperature.     

Development of high performance Cu/ZnO-based catalysts for methanol synthesis and the water-gas shift reaction

Our groups studies on Cu/ZnO-based catalysts for methanol synthesis via hydrogenation of CO₂ and for the water-gas shift reaction are reviewed. Effects of ZnO contained in supported Cu-based catalysts on their activities for several reactions were investigated. The addition of ZnO to Cu-based catalyst supported on Al₂O₃, ZrO₂ or SiO₂ improved its specific activity for methanol synthesis and the reverse water-gas shift reaction, but did not improve its specific activity for methanol steam reforming and the water-gas shift reaction. Methanol synthesis from CO₂ and H₂ over Cu/ZnO-based catalysts was extensively studied under a joint research project between National Institute for Resources and Environment (NIRE; one of the former research institutes reorganized to AIST) and Research Institute of Innovative Technology for the Earth (RITE). It was suggested that methanol should be produced via the hydrogenation of CO₂, but not via the hydrogenation of CO, and that H₂O produced along with methanol should greatly suppress methanol synthesis. The Cu/ZnO-based multicomponent catalysts such as Cu/ZnO/ZrO₂/Al₂O₃ and Cu/ZnO/ZrO₂/Al₂O₃/Ga₂O₃ were highly active for methanol synthesis from CO₂ and H₂. The addition of a small amount of colloidal silica to the multicomponent catalysts greatly improved their long-term stability during methanol synthesis from CO₂ and H₂. The purity of the crude methanol produced in a bench plant was 99.9 wt% and higher than that of the crude methanol from a commercial methanol synthesis from syngas. The water-gas shift reaction over Cu/ZnO-based catalysts was also studied. The activity of Cu/ZnO/ZrO₂/Al₂O₃ catalyst for the water-gas shift reaction at 523 K was less affected by the pre-treatments such as calcination and treatment in H₂ at high temperatures than that of the Cu/ZnO/Al₂O₃ catalyst. Accordingly, the Cu/ZnO/ZrO₂/Al₂O₃ catalyst was considered to be more suitable for practical use for the water-gas shift reaction. The Cu/ZnO/ZrO₂/Al₂O₃ catalyst was also highly active for the water-gas shift reaction at 673 K. Furthermore, a two-stage reaction system composed of the first reaction zone for the water-gas shift reaction at 673 K and the second reaction zone for the reaction at 523 K was found to be more efficient than a one-stage reaction system. The addition of a small amount of colloidal silica to a Cu/ZnO-based catalyst greatly improved its long-term stability in the water-gas shift reaction in a similar manner as in methanol synthesis from CO₂ and H₂.     

费托合成CeO2助Co/SiO2催化剂的失活

在固定床反应器上考察了原粒度(1～3mm)CeO2助Co/SiO2催化剂的费托反应性能,提出了催化剂失活的机理,并采用程序升温还原、X射线衍射和X射线光电子能谱对催化剂进行了表征.结果表明,在1.5MPa,488K和400h-1条件下进行的300h稳定性实验中,原粒度CeO2助Co/SiO2催化剂上的CO平均转化率达到41%,液态烃选择性达到85%,液态烃中C10 烃的质量含量占88%以上.反应器出口的催化剂中有少量的CoO和Co2SiO4生成.催化剂的失活过程受动力学控制而非热力学控制,催化剂的失活机理为:高分散的纳米Co离子在反应器出口高水蒸气压力的作用下,以CoO为中间物种,与水合SiO2作用生成Co2SiO4,即Co H2O→CoO H2,SiO2 H2O→OSi(OH)2,2CoO OSi(OH)2→Co2SiO4 H2O.     

Hydrogenation of Carbon Dioxide on Iron Manganese Catalysts

The synthesis of hydrocarbons from hydrogenation of carbon dioxide has been studied on a series of coprecipitated iron-manganese catalysts. Kinetic measurements, X-ray diffraction, Mössbauer spectroscopy, and temperature-programmed reaction of adsorbed species were used for activity tests and catalyst characterizations. The results showed that the yields of low-carbon olefins decrease, whereas the amount of methane increases with increasing manganese content in catalysts. The conversion to hydrocarbons is suppressed by the reverse water-gas shift (RWGS) reaction equilibrium. Mössbauer spectra and XRD patterns of catalysts after reaction indicate that catalysts are severely oxidized; it is speculated that the olefin producing surface structure in CO hydrogenation may be destroyed by this oxidation. A pulse-reactor study of the Boudouard reaction showed that manganese has the effect of suppressing CO dissociation and thus decreasing carbon content on catalysts. For CO₂ hydrogenation, the affinity to carbon on catalysts is important; therefore manganese is not a good promoter. Among all catalysts tested, pure iron has the best selectivity to olefinic and long-chain hydrocarbons.     

Pseudo-cross-conjugated mesomeric betaines. 1. Synthesis of pseudo-cross-conjugated mesomeric betaines from quinoxaline derivatives

A new method for the synthesis of pseudo-cross-conjugated mesomeric betainic heterocyclic compounds with an angular nitrogen atom has been developed consisting in the reaction of 1,4-dielectrophile — -carbethoxy-2-(3-chloro)quinoxalylacetonitrile with azoles. Experimental regularities have been studied and a reaction mechanism has been proposed including the stage of formation of an ylide from a quaternary azolium salt. A pseudo-crossconjugated mesomeric betainic heterocyclic compound containing a thiazole ring compound has been synthesized for the first time.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1528–1533, November, 1992.     

Enhanced methane decomposition over transition metal-based tri-metallic catalysts for the production of COx free hydrogen

In this study, COx-free hydrogen production via methane decomposition was studied over Cu–Zn-promoted tri-metallic Ni–Co–Al catalysts. The catalysts have been prepared by the constant pH co-precipitation method, and the nominal Ni metal loading was fixed at 50 wt % along with other metals at 10 wt% each. The catalyst activity for methane decomposition reaction was examined in a reactor between 400 °C and 700 °C and at atmospheric pressure. Different techniques such as N₂-physisorption, X-ray diffraction, H₂-TPR SEM, TEM, ICP-MS, TGA, and Raman spectroscopy were applied to characterize the catalysts. The relation between the catalyst composition and their catalytic activity has been investigated. The controlled synthesis has resulted in a series of catalysts with a high surface area. Ni–Co–Cu–Zn–Al was the most active and productive catalyst. Various characterizations indicate that the promotional effects of Cu–Zn interaction were the critical factor in catalysts' activity and stability. Ni–Co–Cu–Zn catalyst gave the highest methane conversion of 85% at 700 °C. Zn addition improves the stability of the catalyst by retaining the active metal size during the decomposition reaction. The catalyst was active for 80 h of stability study. The rapid deactivation of the Ni–Co catalyst was due to the sintering of the catalyst at 650 °C. Moreover, carbon species accumulated during the methane decomposition reaction depend on the catalysts' composition. Zn promotes the growth of reasonably long and thin carbon nanotubes, whereas the diameter of carbon nanotubes on unpromoted catalysts was large.     

A novel multi-component synthesis of 4-arylaminoquinazolines

A new multi-component synthesis of 4-arylaminoquinazolines from the reaction of 2-aminobenzamide, orthoesters, and substituted anilines in the presence of catalytic amounts of Keggin-type heteropolyacids is reported. The effects of reaction conditions and different heteropolyacids have been studied.     

Synthesis of 1,3-cyclohexadienes by tandem diene-alkyne metathesis: improved procedure

A practical synthesis of 2-substituted 1,3-cyclohexadienes by the cross enyne metathesis between alkynes and 1,5-hexadiene is reported. The isolation of the 1,3-cyclohexadienes has been hampered by the formation of an inseparable triene by-product. The use of a second consecutive cross alkene metathesis to give water-soluble products allowed removal of this by-product. Using this one-pot procedure, a synthesis of cyclohexadienes from simple starting materials was developed. The procedure was used in a three-step synthesis of a functionalized tetrahydroquinoline using Pd(II)-catalyzed chloroacetoxylation (Bäckvall reaction) for cyclohexadiene functionalization.     

Synthesis of 2-Oxazolines from Ring Opening Isomerization of 3-Amido-2-Phenyl Azetidines

Chiral 2-oxazolines are valuable building blocks and famous ligands for asymmetric catalysis. The most common synthesis involves the reaction of an amino alcohol with a carboxylic acid. In this paper, an efficient synthesis of 2-oxazolines has been achieved via the stereospecific isomerization of 3-amido-2-phenyl azetidines. The reactions were studied in the presence of both Brønsted and Lewis acids, and Cu(OTf)₂ was found to be the most effective.     

Synthesis of 1,3-dialkylurea from ethylene carbonate and amine using calcium oxide

Several basic metal oxide catalysts were tested for the synthesis of 1,3-disubstituted urea from ethylene carbonate (EC) and amine. Among the catalysts used, CaO has been found to be an excellent recyclable catalyst for the reaction. It has been suggested that strongly basic property of CaO results in its high activity. Disubstituted ureas are obtained from propylamine and butylamine with high yields at 100 °C. Slightly higher reaction temperatures are necessary for obtaining good yields from amines having larger molecular weights and urea is not produced from dibutylamine as a secondary amine. Propylene carbonate can be used instead of EC for the reaction. A reaction mechanism was proposed, which involves reaction between EC and amine giving a carbamate followed by catalytic reaction between the carbamate and amine, yielding 1,3-disubstituted urea. It is suggested that the latter reaction is the rate-determining step. On the basis of this reaction mechanism, the synthesis of unsymmetric urea was also examined. 2-Hydroxyethyl butylcarbamate is selectively produced from EC with butylamine in the absence of the catalyst at a low temperature and reacts with benzylamine producing 1-butyl-3-benzylurea along with symmetric dialkyl ureas.     

Cu(I)-catalyzed reaction of diazo compounds with terminal alkynes: a direct synthesis of trisubstituted furans

A method for the synthesis of tri-substituted furans has been developed based on Cu(I)-catalyzed reaction of terminal alkynes with β-keto α-diazoesters. This method for the synthesis of 2,3,5-trisubstituted furans is operationally simple and applicable to wide substrate scope. Moreover, this synthesis employs cheap Cu(MeCN)₄PF₆ as the catalyst and no additional ligand is needed. Similar reaction has also been applied to ethyl (E)-2-diazo-3-(methoxyimino)butanoate for the synthesis of 2,3,5-trisubstituted N-methoxypyrroles with limited success.     

Synthesis of Ammonia in a Strong Electric Field Discharge at Ambient Pressure

The plasma synthesis of ammonia has been studied in a nitrogen–hydrogenplasma using a strong electric field discharge at ambient pressure andtemperature. With this method, N₂ and H₂ molecules are ionized anddissociated and a large number of free atoms, ions, and radicals areformed in a nonequilibrium plasma after inelastic collisions. The finalproduct was mainly ammonia, including a small amount of hydrazine. WhenMgO powder, used as a catalyst, was smeared on the surface of the electrodeplates, the yields of ammonia increased about 1.54–1.75 times andreached 5000 ppm (0.5% v/v). In this way, plasma synthesis of ammonia atambient pressure is realized and a new method is provided for inorganicsynthesis, which consumes little energy and simplifies the process.     

Contrasted effect of CO on the metal‐catalyzed cycloisomerization of O‐tethered enynes derived from monoterpenes

The CO‐bubbling effect in cycloisomerization reactions of enynes derived from monoterpenes has been studied using PtCl₂, [Rh₂Cl₂(CO)₄] and AuCl₃ as catalytic systems. All the precursors are efficient catalysts for the cycloisomerization of O‐tethered enynes. The reaction proceeds through exo‐dig and endo‐dig pathways, which are consistent with the exclusive coordination of the alkyne triple bond to the metal center. The CO ligand not only increases the reaction rates but also induces significant variations in the two reaction pathways. Notably, this effect is also strongly dependent on the nature of the starting enyne. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis,thermal stability and mass spectra of 2-trihalomethyl-1,3,5-dithiazin-4-ones and their 2,3-dihydro derivatives

A method has been proposed for the synthesis of 2-trihalomethyl-1, 3,5-dithiazines based on the reaction of 1 1, -dithiols with 1, 1-dichloro- and I -chloroalkyl isocyanates. The thermal stability and mass spectra of these compounds were studied.Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 252660 Kiev, Ukraine. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp, 996–1000, July, 1995. Original article submitted February 21, 1995.     

Copper promoted C-S and C-N cross-coupling Reactions:The synthesis of 2-(N-Aryolamino)benzothiazoles and 2-(N-Aryolamino)benzimidazoles

The synthesis of 2-(N-aryolamino)benzothiazoles and 2-(N-aryolamino)benzimidazoles has been accomplished in the presence of copper catalyst. These reactions involve C-S and C-N cross-coupling reaction. All electron donating and withdrawing substituent's readily underwent the reaction to give target products in good to excellent yield. In addition, the reaction also gave target product in high yield with bulk scale.     

低压合成甲醇催化剂母料变色点性质的研究

研究了合成甲醇催化剂母料陈化期间pH值的变化情况，尤其是母料变色点前后pH值的变化，考察了反应pH值及反应温度对变色时间及催化剂活性的影响。结果表明，合成甲醇催化剂母料在陈化期间pH值一直在改变，在变色点附近出现了pH值的一个极小值，与其相应的是在母料变色前后催化剂的活性发生了明显的变化，因此，在变色点前后母料的组成及结构都发生了明显的变化。升高反应温度有利于母料结构的调变，升高反应pH值不利于母料结构的这种变化。通过本实验确定了催化剂母料在并流情况下最佳沉淀pH值范围为7.5～8.5，最佳沉淀温度大于80 ℃。     

A divergent synthesis of - and -carbocyclic 4′-fluoro-2′,3′-dideoxynucleosides as potential antiviral agents

- and -Carbocyclic 4′-fluoro-2′,3′-dideoxynucleosides have been synthesized from 2, which can be conveniently prepared from 1,2:5,6-di-O-isopropylidene- -mannitol 1 in eight steps. Ruthenium-catalyzed ring-closing metathesis has been employed in the synthesis of -nucleosides, whereas the -series have been obtained through an intramolecular nucleophilic substitution reaction. The Mitsunobu condensation was used as a general tool for the synthesis of both purine and pyrimidine nucleosides.     

Totally regio- and stereoselective synthesis of (E)-3-arylidene-3,4-dihydro-2H-1,4-benzoxazines under palladium catalyst

A new, one-pot palladium catalyzed reaction has been developed for the general synthesis of (E)-3-arylidene-3,4-dihydro-2H-1,4-benzoxazines at room temperature. The reaction procedure tolerates various functional groups. The method is characterized by regio- and stereoselectivity, operational simplicity, mild reaction conditions, and short reaction time.     

Effect of the surface area of platinum on the activity of a bifunctional aluminoplatinum catalyst in the synthesis of alkylimidazoles from diamines and carbonyl acids

An investigation has been conducted into the effect of the acid and dehydrogenating functions of an aluminoplatinum catalyst on the synthesis of 2-methylimidazole from ethylenediamine and acetic acid. It has been established that formation of the intermediate 2-methylimidazoline involves the acid Al₂O₃ centers and its rate of formation is greater than the rate of its subsequent dehydrogenation to 2-methylimidazole on the Pt centers. The symbatic nature of the variations in the 2-methylimidazole yield and the surface area of the platinum in the aluminoplatinum catalyst has been demonstrated.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 1992–1996, September, 1992.     

CO2／H2和（CO／CO2）＋H2低压合成甲醇催化过程的本质

通过在Ｃｕ／ＺｎＯ／Ａｌ２Ｏ３催化剂上ＣＯ２＋Ｈ２，ＣＯ＋Ｈ２和（ＣＯ／ＣＯ２）＋Ｈ２催化反应动力学研究对合成甲醇动力学和反应机理进行了细致分析，提出合成甲醇的反应机理，解释了在（ＣＯ／ＣＯ２）＋Ｈ２合成甲醇过程中少量ＣＯ２的作用及合成甲醇的直接碳源。