乙酸异丙酯的合成

以乙酸和异丙醇为原料,硫酸氢钠为催化剂,合成了乙酸异丙酯;考察了反应时间、酸醇比、催化剂用量、带水剂用量对酯化率的影响,确定了最佳酯化反应条件:反应时间60min,酸醇的物质的量的比1∶0.8,催化剂用量0.8g,带水剂用量8mL.在最佳反应条件下,酯化率最高可达84.3%.     

乙酸正丁酯的合成

以乙酸和正丁醇为原料,在硫酸氢钾催化下合成了乙酸正丁酯;考察了反应时间、醇酸比、催化剂用量、带水剂用量及催化剂的重复使用对酯化率的影响.结果表明:当正丁醇用量为0.1mol,乙酸用量为0.135mol,催化剂硫酸氢钾用量为0.8g,带水剂环己烷用量为8mL时,反应的酯化率达95.2%.     

固体超强酸ZrO_2/S_2O_8~(2-)催化合成乙酸正己酯

以固体超强酸ZrO2/S2O2-8为催化剂,乙酸和正己醇为原料合成了乙酸正己酯,考察了反应条件对酯化率的影响.结果表明,最佳反应条件为:醇酸摩尔比1.4,催化剂用量0.5g(当乙酸用量为0.1mol时),带水剂苯15mL,在110～118℃反应1.5h,其酯化率达92%以上.该方法的优点是酯化率高,催化剂可重复使用且基本不腐蚀设备.     

强酸型离子交换膜催化合成丙酸异戊酯

以HF－101型强酸型离子交换膜为催化剂，对丙酸与异戊醇的催化反应进行了研究，考察了反应时间,催化剂用量，酸醇摩尔比及催化剂的套用次数对酯化率的影响，探讨其最佳反应条件为：酸醇摩尔比1：1．3，反应时间90min，催化剂用量为反应物总质量的6．5％，反应温度为回流温度，酯化率98％，催化剂套用8次后酯化率仍在80％以上。     

对硝基苯甲酸乙酯的合成

以硫酸氢钾为催化剂,研究了对硝基苯甲酸和乙醇反应生产对硝基苯甲酸乙酯的合成工艺.考察了催化剂用量、反应时间、醇酸物质的量之比、带水剂用量以及催化剂重复使用次数对酯化率的影响,确定了最佳反应条件.当对硝基苯甲酸的用量为0.015mol,无水乙醇为0.060mol,反应时间为2.0h,带水剂环己烷用量为15mL,催化剂硫酸氢钾的用量为0.4g,对硝基苯甲酸乙酯的酯化率可达到91.65%.在此条件下,催化剂的催化活性高,反应条件温和,该合成方法简便,产品收率优良,催化剂可重复使用,且价格低廉.     

磷酸钛固载磷钨酸非均相催化合成异戊酸己酯

通过在300℃下焙烧2h制备了磷酸钛固载15%磷钨酸H3PW12O40(简记为HPW)非均相酯化催化剂HPW/Ti3(PO4)4;采用红外光谱仪分析了催化剂的结构;基于异戊酸与正己醇的酯化反应考察了催化剂用量、n(正己醇)∶n(异戊酸)、反应时间、带水剂种类和催化剂重复使用性能等因素对酯化率的影响.结果表明,该催化剂催化合成异戊酸己酯的适宜反应条件为:0.2mol异戊酸,催化剂用量0.6g,n(正己醇)∶n(异戊酸)=1.6∶1,反应时间4.5h,环己烷10mL;相应的酯化率达95.1%.与此同时,该催化剂循环利用6次后酯化率不低于84%.     

树脂D732负载磷钨酸催化合成水杨酸酯

在水杨酸和正丁醇反应中,采用强酸性阳离子树脂D732负载磷钨酸为催化剂,合成了水杨酸酯。考察了醇/酸的摩尔比、反应时间、反应温度、催化剂的用量和催化剂的重复使用性等因素对反应酯化率的影响。结果表明,在反应温度为110℃,反应时间3h,酸/醇摩尔比为1:3,催化剂质量占水杨酸总质量的20%的较优条件下,酯化率达93.2%。催化剂不经处理重复使用4次,酯化率均在83%以上。依据该较佳的工艺条件,进一步催化合成其它水杨酸酯,酯化率均超过82%,表明D732负载磷钨酸具有良好催化效果。     

自制Ti/W-MCM-41介孔分子筛催化制备乳酸戊酯

采用自制的介孔分子筛Ti/W-MCM-41催化乳酸与正戊醇的酯化反应,合成了乳酸正戊酯;利用红外光谱仪分析了催化剂的化学特征,考察了分子筛的WO3质量分数、催化剂用量、醇酸物质的量比、反应时间、催化剂重复使用性能等因素对目标产物酯化率的影响.结果表明,在nSi∶nTi=30∶1,WO3质量分数10%,550℃下焙烧6h条件下制得的催化剂具有良好的催化性能;其催化合成乳酸正戊酯适宜的反应条件为:0.2mol乳酸,催化剂用量0.5g,n(正戊醇)∶n(乳酸)=1.6∶1,反应时间100min,酯化率可达94.4%.该催化剂使用7次酯化率仍可达86.6%.     

固体超强酸ZrO2/S2O28-催化合成乙酸正己酯

以固体超强酸ZrO2／S2O8^2-为催化剂，乙酸和正己醇为原料合成了乙酸正己酯，考察了反应条件对酯化率的影响,结果表明，最佳反应条件为：醇酸摩尔比1．4，催化剂用量0．5g(当乙酸用量为0．1mol时)，带水剂苯15mL，在110-118℃反应1．5h，其酯化率达92％以上．该方法的优点是酯化率高，催化剂可重复使用且基本不腐蚀设备．     

二氧化硅负载硫酸氢钠催化合成壬酸乙二醇单酯

研究了以二氧化硅负载硫酸氢钠为催化剂,壬酸和乙二醇为原料合成壬酸乙二醇单酯的工艺.考察了酸醇物质的量、催化剂用量、反应时间、反应温度等对壬酸酯化率的影响,结果表明,合成壬酸乙二醇单酯的优化条件为:壬酸与乙二醇的物质的量为1∶3,催化剂的用量为反应物料总质量的5%,反应时间为4h,反应温度为90℃,在此条件下,酯化率可达92%以上,通过红外光谱验证了目标产物.催化剂具有一定的重复使用活性.     

Titanium catalysis in the Ugi reaction of alpha-amino acids with aromatic aldehydes

[reaction: see text] Ugi reaction between an (S)-alpha-amino acid, an aromatic aldehyde, and an isonitrile proceeds best under catalysis by TiCl(4) in MeOH. The sense of diastereoinduction is (S,S).     

High Catalytic Activity of Nitrogen and Sulfur Co‐Doped Nanoporous Graphene in the Hydrogen Evolution Reaction

Chemical doping has been demonstrated to be an effective way to realize new functions of graphene as metal‐free catalyst in energy‐related electrochemical reactions. Although efficient catalysis for the oxygen reduction reaction (ORR) has been achieved with doped graphene, its performance in the hydrogen evolution reaction (HER) is rather poor. In this study we report that nitrogen and sulfur co‐doping leads to high catalytic activity of nanoporous graphene in HER at low operating potential, comparable to the best Pt‐free HER catalyst, 2D MoS₂. The interplay between the chemical dopants and geometric lattice defects of the nanoporous graphene plays the fundamental role in the superior HER catalysis.     

手性氨基酚催化二乙基锌对芳香醛的不对称加成反应

用易得的原料合成了4个手性氨基酚，这些化合物成功地催化了二乙基锌对醛 的不对称加成反应．其中1a催化间氯苯甲醛和二乙基锌的加成反应获得了较高的化 学产率(95％)和较好的ee值(57％)．     

Bifunctional and monofunctional catalysis in the CNDO/2 approximation: Formamidine acid-base and base catalysed 1,3-proton transfers in propene

The bifunctional acid-base and monofunctional base catalysis by formamidine of 1,3-proton transfer reactions in propene has been studied with the CNDO/2 MO-method. Energy profiles for both types of catalysis were studied, and no reaction intermediate was found in either case. In agreement with orbital correlation considerations, bifunctional catalysis is preferred over monofunctional catalysis. Comparison is made with another reaction in which simultaneous transfer of two protons occurs. The mechanism of bifunctional monofunctional catalysis is discussed.     

Two-metal-ion mechanism for hammerhead-ribozyme catalysis

The hammerhead ribozyme is one of the best studied ribozymes, but it still presents challenges for our understanding of RNA catalysis. It catalyzes a transesterification reaction that converts a 5',3' diester to a 2',3' cyclic phosphate diester via an S(N)2 mechanism. Thus, the overall reaction corresponds to that catalyzed by bovine pancreatic ribonuclease. However, an essential distinguishing aspect is that metal ions are not involved in RNase catalysis but appear to be important in ribozymes. Although various techniques have been used to assign specific functions to metals in the hammerhead ribozyme, their number and roles in catalysis is not clear. Two recent theoretical studies on RNA catalysis examined the reaction mechanism of a single-metal-ion model. A two-metal-ion model, which is supported by experiment and based on ab initio and density functional theory calculations, is described here. The proposed mechanism of the reaction has four chemical steps with three intermediates and four transition states along the reaction pathway. Reaction profiles are calculated in the gas phase and in solution. The early steps of the reaction are found to be fast (with low activation barriers), and the last step, corresponding to the departure of the leaving group, is rate limiting. This two-metal-ion model differs from the models proposed previously in that the two metal ions function not only as Lewis acids but also as general acids/bases. Comparison with experiment shows good agreement with thermodynamic and kinetic data. A detailed analysis based on natural bond orbitals (NBOs) and natural energy decomposition (NEDA) provides insights into the role of metal ions and other factors important for catalysis.     

Pd catalysis on dendronized solid support: generation effects and the influence of the backbone structure

Recent studies revealed that catalysts, prepared on dendronized support, frequently exhibit enhanced activity and selectivity as compared to their non-dendronized analogues. Regretfully, in early studies of the supported dendritic catalysis, no particular attention was paid to the coordinative nature of the dendritic backbone. In this study, we functionalized Wang polystyrene support with three types of dendritic templates: poly(aril benzyl ether), poly(aryl benzyl thioether), and poly(aryl benzyl amine). These dendronized resins were further decorated with phosphine ligands on the periphery and complexed with a Pd(0) catalytic precursor. The catalysis of the Heck and Suzuki reactions of bromobenzene with the first to third generation supported dendritic catalysts was examined and compared to that of the non-dendritic analogues. All of the examined reactions revealed a positive dendritic effect, reflected in up to 5-fold increase in yield, in the most prominent case. The reasons for the observed effect are the proximity of the ligating sites translated into reduced cross-linking and, probably, the increased distance of the catalyst from the polymer matrix. We proved, however, that the latter could not be achieved with a linear spacer. Although the Suzuki reaction was rather insensitive to the backbone structure, the Heck reaction catalysis at 80 degrees C exhibited substantial sensitivity to the nature of the dendritic backbone, with the polyether structure demonstrating the best outcome. This is the first demonstration of the influence of the coordinative ability of the backbone on the activity of a supported dendritic catalyst.     

Chloromethylation of 2-chloroethylbenzene catalyzed by micellar catalysis

The chloromethylation reaction of 2-chloroethylbenzene was performed successfully by micellar catalysis in the biphasic oil/water system. The effects of anionic, cationic and non-ionic surfactants on the reaction were compared. The mechanism of chloromethylation reaction and the mechanism of micellar catalysis were investigated. The results show that the micellar catalysis is an effective way to realize the chloromethylation of 2-chloroethylbenzene, and the cationic surfactant shows the most effectiveness. The longer the hydrophobic chain of the cationic surfactant is, the better the catalysis effect will be, and the addition of inorganic electrolyte into the aqueous phase can markedly promote the catalysis effect.     

Cooperative catalysis: Condensation-aromatization for synthesis of 2-(4-nitrophenyl)-1H-benzimidazole by silica immobilized Brønsted-Lewis acidic ionic liquid (Si-BLAIL)

Herein, pleasing the advantageous of both Brønsted and Lewis acidic site of Si-BLAIL the condensation-aromatization reaction has been carried out. The striking distinctiveness of work is optimum reaction condition, easy work-up, high yield, catalyst recyclability, non-inertness of reaction flask, simple catalyst loading method. The decreases in the amount of catalyst and reaction time shows good to high (71%–93%) yield suggests about the involvement of some interesting mechanism such as cooperative catalysis. The mechanism has been hypothesizes as, the Si-BLAIL increase the efficiency of condensation reaction possibly by providing the proton in 2-position of cationic imidazolium ring of BLAIL through the hydrogen bond interaction with carbonyl group and nucleophilic activation during aromatization by hydrogen bond acceptor ability of Lewis adduct anion of BLAIL. The catalyst Si-BLAIL shows massive affirm for industrial applications. The Si-BLAIL has identified as the best acid catalyst for 2-(4-nitrophenyl) benzimidazole synthesis with additional benefits of cooperative catalysis.     

Ruthenium- and rhodium-catalyzed direct carbonylation of the ortho C-H bond in the benzene ring of N-arylpyrazoles

The direct carbonylation of C-H bonds in the benzene ring of N-phenylpyrazoles via catalysis by ruthenium or rhodium complexes is described. The reaction of N-phenylpyrazoles with carbon monoxide and ethylene in the presence of Ru(3)(CO)(12) or Rh(4)(CO)(12) resulted in the site-selective carbonylation of the ortho C-H bonds in the benzene ring to give the corresponding ethyl ketones. A variety of functional groups on the benzene ring can be tolerated. N-Phenylpyrazoles have higher reactivities than would be expected, based on the pK(a) values of the conjugate acid of pyrazole. The choice of solvent for this reaction is significant, and N, N-dimethylacetamide (DMA) gives the best result.     

Study of the effect of the ligand structure on the catalytic activity of Pd@ ligand decorated halloysite: Combination of experimental and computational studies

Taking advantage of computational chemistry, the best diamine for the synthesis of a multi‐dentate ligand from the reaction with 3‐(trimethoxysilyl) propylisocyanate (TEPI) was selected. Actually, predictive Density Functional Theory (DFT) calculations provided the right diamino chain, i.e. ethylenediamine, capable to sequester a palladium atom, together with the relatively polar solvent toluene, and then undergo the experiments as a selective catalytic agent. The ligand was then prepared and applied for the decoration of the halloysite (Hal) outer surface to furnish an efficient support for the immobilization of Pd nanoparticles. The resulting catalyst exhibited high catalytic activity for hydrogenation of nitroarenes. Moreover, it showed high selectivity towards nitro functional group. The study of the catalyst recyclability confirmed that the catalyst could be recycled for several reaction runs with only slight loss of the catalytic activity and Pd leaching. Hot filtration test also proved the heterogeneous nature of the catalysis.