Esterification and Chemoselective Synthesis of R-Tetrahydrothiazo-2- thione-4-carboxylic Esters Catalyzed by TiCl4

A series of esters of R-tetrahydrothiazo-2-thione-4-carboxylic acid[R-TTCA] was synthesized by direct esterification of R-TTCA with alcohols(CH3OH,C2H5OH,n-C3H7OH,i-C3H7OH,n-C4H9OH,sec-C4H9OH)in the presence of TiCl4 as the catalyst at room temperature without using any other solvent or dehydrant in high yields,91.6%-99.1% for primary alcohols and 55%- 80% for secondary alcohols.The catalyst has a strong chemoselective activity for the esterification of primary alcohols with R-TTCA in the presence of secondary alcohols.Owing to high yield,high chemoselectivity,and mild conditions used,this is an efficient method for the esterification of primary alcohols with R-TTCA.     

氧化铝负载的银纳米颗粒高选择性催化合成亚胺(英)

The oxidative dehydrogenation of alcohols to aldehydes catalyzed by Ag nanoparticles supported on Al₂O₃ was studied.The catalyst promoted the direct formation of imines by tandem oxidative dehydrogenation and condensation of alcohols and amines.The reactions were performed under mild conditions and afforded the imines in high yield（up to 99%） without any byproducts other than H₂O.The highest activity was obtained over 5 wt%Ag/Al₂O₃ in toluene with air as oxidant.The reactions were also performed under oxidant-free conditions where the reaction was driven to the product side by the production of H₂ in the gas phase.The use of an efficient and selective Ag catalyst for the oxidative dehydrogenation of alcohol in the presence of amines gives a new green reaction protocol for imine synthesis.     

Kinetic and thermodynamic studies of the esterification of acidified oil catalyzed by sulfonated cation exchange resin

This study describes the kinetics and thermodynamics of the esterification of acidified oil with methanol catalyzed by sulfonated cation exchange resins(SCER). The effects of the mass ratio of methanol to acidified oil,reaction temperature,and catalyst loading were studied to optimize the conditions for maximum conversion of free fatty acids(FFAs). The results showed that the optimal conversion rate of FFAs was 91.87% at the mass ratio of methanol to acidified oil of 2.5:1.0,reaction temperature of 65.0 °C,catalyst loading of 5.0 g and reaction time of 8.0 h. The external and internal mass transfer resistances were negligible based on the experimental results and a pseudo-homogeneous kinetic model was proposed for the esterification. The activation energy and thermodynamic parameters including G,S and H were determined. The conversion rates of FFAs obtained from the established model were in good agreement with the experimental data.     

CATALYTIC ESTERIFICATION OF CARBOXYLIC ACIDS WITH ALCOHOLS BY SULFO-POLYVINYL CHLORIDE

Polyuinyl Chloride reacted with chlorosulfonic acid to form a polymer catalyst PVC-SO3H. This polymer catalyst was found to have high activity for esterification reaction between carboxylic acids and alcohols. This paper deals with the conditions in synthesis of n-butylacetate catalyzed with PVC-SO3H. The PVC-SO3H was used as a catalyst for preparing 11 esters of acetic acid, propiofnic acid and butyric acid with the yields of 82-92%.     

N-Bromosuccinimide Catalyzed One-pot and Rapid Synthesis of Acetamidobenzyl Naphthols under Mild and Solvent-free Conditions

An efficient, facile and expeditious direct protocol for the preparation of acetamidobenzyl naphthols employing a multi-component and one-pot condensation reaction of 2-naphthol, benzaldehydes, and acetamide in the presence of N-bromosuccinimide (NBS) under thermal and microwave irradiation conditions has been described. The present protocol with NBS catalyst is convincingly superior to the recently reported catalytic methods.     

固体酸Fe2(SO4)3催化合成丙酸异戊酯

Solid acid ferric sulphate Fe2(SO4)3 was prepared and used for the study of the catalytic synthesis of iso-amyl propionate. The optimun reaction conditions were follows: the ratio of amount of substance n(iso-amylalcohol) : n(propionic acid) = 1.5, the reaction time 2h, the catalyst quantity 1.5g, and dewatering solvent toluene 10ml. The yield was 97.2% under the optimum reaction conditions. The catalyst being of high catalytic activity for the esterification reactions was prepared very easily and could be used repeatedly.     

Zirconyl chloride promoted highly efficient solid phase synthesis of amide derivatives

An efficient solid phase route for the synthesis of amide derivatives by the reaction of carboxylic acids with urea in the presence of catalytic amount of zirconyl chloride under microwave irradiation conditions was described.In this way,a range of interesting amide derivatives was obtained in good to excellent yields.The catalyst was recycled with fresh reactants and it gave almost similar results without significant loss of activity up to the third run.     

A Novel Method for Synthesizing 6-Chloro and 6-Methoxypurinenucleoside

Starting from tetraacetylribofuranose (Ⅰ) and 6-chloropurine (Ⅲ), in the presence ofp-toluenesulfonic acid as catalyst, the intermediate 2',3',5'-tri-O-acetyl-6-chloropurine nucleoside (Ⅲ) was synthesized for the first time under microwave irradiation in the yield of 80.1%. The title compounds 6-chloro-9-β-D-purinenucleoside (Ⅳ) and 6-methoxy9-β-D-purinenucleoside (Ⅴ) were easily obtained by treatment the intermediate (Ⅲ) with NH3/CH3OH and Na2CO3/CH3OH in the yields of 78.8% and 76.9%, respectively. Structures of Ⅳ and Ⅴ have been identified by 1H NMRand elementary analysis. The optimal conditions for condensation were as follows: n(Ⅰ): n(Ⅱ)= 1: 1, m(TsOH):m(6-chloropurine)=3 × 10-2, microwave irradiation at 595 W for 4.5 min, at 462 W for 1 min, at 119 W for 0.5 min;aminolysis condition for Ⅳ: room temperature for 5 min; alkaline hydrolysis conditions for Ⅴ: reflux for 5 h.     

Microwave Irradiation Promoted Synthesis of Aryloxy Acetic Acids

Several aryloxy acetic acids were synthesized under microwave irradiation. The factors, which affect the reaction, were investigated and optimized. It was revealed that the best yields(92. 7%--97.4%) were obtained when the molar ratio of the reactants was n(ArOH) : n(NaOH) : n(CICH2CO2H) = 1：2.5： 1.2 with microwave irradiation power of 640 W for 65--85 s.     

SYNTHESIS OF HIGHER ALCOHOLS ON Co-Co-Y CATALYSTS

Hydrogenation of carbon monoxide has been studied under 15 MPaon modified Co-Cu-Y catalysts. Molybdenium was very effective for promotingcatalytic activity, and the synergistic presence of Co, Cu and Mo was necessaryfor the good catalytic performance in the synthesis of higher alcohols C_(2+)OH.Under our experimental conditions, a yield of 175 g/kg cat/h of mixed alcohols(C_1-C_5) was obtained with a C_(2+)OH proportion of 45％ in weight. A stronginteraction between CuO, CoO_y and MoO_x in the modified catalyst was ob-served. The presence of MoO_x stabilized the Y_2O_3 structure of the catalyst duringthe syngas reaction under high pressure illustrated by the X-ray diffractiontests.     

磺化聚苯乙烯的无溶剂制备及其催化性能研究

本文以聚苯乙烯为底物,发烟硫酸为磺化剂,在无溶剂和无催化剂条件下制得了磺化聚苯乙烯,对其酸度和结构性能进行了表征,并详细研究了其催化肉桂酸与正丁醇酯化反应的性能。在醇酸摩尔比为15∶1、环己烷作带水剂的条件下,分别考察了催化剂用量、回流温度、回流时间对酯化反应的影响,优化了反应条件,并在优化条件下,探究了其重复催化使用性能,结果表明,该催化剂重复使用15次,产率基本保持不变,仍可达到69.6%。该催化剂对肉桂酸与其他低级脂肪醇的酯化反应也具有良好的催化效果,是一种环境友好型具有潜在应用价值的固体酸催化剂。     

微波促进酸性离子液体催化水杨酸酯化

用自制的硫酸氢1-甲基-3-(3-磺酸基丙基)咪唑([MIMPS]HSO4)酸性离子液体作为水杨酸与醇的酯化反应催化剂,考察了温度、时间、物料配比和离子液体用量等因素对酯化反应的影响,优化的最佳反应条件为: 微波辐射时间20 min,反应温度95 ℃,醇与酸摩尔比3∶1(水杨酸的量为0.02 mol),[MIMPS]HSO4用量10 mmol,水杨酸甲酯的产率和选择性分别为91.9%和99.0%。 离子液体回收循环使用4次,催化效率不变。 与热催化酯化反应相比,微波辐射可缩短反应时间;水杨酸与不同碳链醇的酯化产率随着碳链的增加而降低,同碳链的伯醇酯化率比仲醇高。     

微波辐射固体酸催化合成己二酸二正辛酯

采用微波辐射技术 ,以活性炭担载对甲苯磺酸为催化剂 ,由己二酸和正辛醇直接酯化合成己二酸二正辛酯。用正交试验研究了各反应因素对反应转化率的影响 ,确定其最佳反应条件为 :己二酸的用量 1mmol,正辛醇的用量 4mmol,催化剂用量为 0 .8g ,微波功率 6 0 0W ,辐射时间 45s ,转化率为 99.3 % ,催化剂且可重复使用。     

Catalytic Synthesis of Fused 1,4-Dihydropyridines and 1,4-Dihydropyridine Derivatives Using Preyssler Heteropolyacids Catalyst

An efficient and convenient method for the synthesis of 1,4-dihydropyridines from β-dicarbonyl compounds, aldehydes, and ammonium acetate and the synthesis of fused 1,4-dihydropyridines from dimedone in the presence of Preyssler heteropolyacid catalyst are reported under reflux conditions with good to excellent yields. Preyssler heteropolyacid catalyst is easily prepared, stable (up to 300 °C), reusable, efficient, green and inexpensive.     

ZrOCl2 x 8H2O: an efficient, cheap and reusable catalyst for the esterification of acrylic acid and other carboxylic acids with equimolar amounts of alcohols

Esterifications of carboxylic acids with equimolar amount of alcohols could be efficiently catalyzed by ZrOCl(2) x 8H(2)O. Acrylate esters were obtained in good yields under solvent-free conditions at ambient temperature. The esterification of other carboxylic acids with alcohols also proceeded at ambient temperature or at 50 oC to afford esters in high yields. If the esterification was performed in toluene under azeotropic reflux conditions to remove water, both the catalytic activity of ZrOCl(2) x 8H(2)O and the rate of esterification could be increased greatly. Furthermore, in the present catalytic system, the esters could be easily separated from the reaction mixtures and the catalyst could be easily recovered and reused.     

Kinetics and reaction mechanism of phenol hydroxylation catalyzed by La-Cu_4FeAlCO_3

Phenol hydroxylation is an industrially important reaction, whose main products are catechol and hy-droquinone being diverse applications which are im-portant intermediates for perfumes, drugs, and phar-maceuticals and so on[1]. The processes using H2O2 a…     

Papain catalyzed estehification of alanine by alcohols and diols

Papain catalyzed esterification of Boc-Ala-OH with various alcohols and diols under biphasic conditions was investigated. Long-chain diols HO(CH₂)nOH gave good yields of esterification up to n=10 whereas the homologous alcohols C_nH_2n+1OH condensed well only for n = 2, 4, 6. Esterification with functionnalized primary alcohols is also described.     

NaHSO4·H2O催化合成苯甲酸甲酯

以 Na HSO4 · H2 O催化苯甲酸与甲醇的酯化反应 ,合成了苯甲酸甲酯。研究结果表明 ,Na HSO4 · H2 O具有较高的催化活性。考察了苯甲酸 /甲醇摩尔比、催化剂用量及反应时间对酯产率的影响。在优化反应条件 [n(苯甲酸 )∶n(甲醇 )∶n( Na HSO4 ·H2 O) =1∶ 2∶ 0 .2 9,回流8h]下 ,苯甲酸甲酯产率达 85.3 %。     

Esterification of phthalic anhydride with 1-butanol and 2-ethylhexanol catalyzed by heteropolyacids

Esterification of phthalic anhydride with 2-ethylhexanol and 1-butanol and ester decomposition of dioctyl phthalate (DOP) in presence of Keggin; H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₄SiMo₁₂O₄₀, Wells–Dawson; H₆P₂W₁₈O₆₂, H₆P₂W₁₇MoO₆₂ and Preyssler; H₁₄[NaP₅W₂₉MoO₁₁₀], H₁₄[NaP₅W₃₀O₁₁₀], type heteropolyacids have been investigated. The heteropolyacids with Preyssler and Wells–Dawson structures and their molybdenum substituted derivatives show higher activity in esterification and ester decomposition reactions than Keggin type heteropolyacids. A complete conversion of phthalic anhydride to dioctyl phthalate and dibutyl phthalate are achieved in 2 h in presence of molybdenum substituted Preyssler heteropolyacid. In the decomposition of dioctyl phthalate in the presence of Preyssler heteropolyacid, 2-ethylhexene is formed in quantitative yield.