Synthesis of 2,2,5,5‐Tetrasubstituted 1,4‐Dioxa‐2,5‐disilacyclohexanes via Organotin(IV)‐Catalyzed Transesterification of (Acetoxymethyl)alkoxysilanes

(Acetoxymethyl)silanes 2 , 7 a – c , and 10 a – c with at least one alkoxy group, of the general formula (AcOCH₂)Si(OR)_3?n(CH₃)_n (R: Me, Et, iPr; n=0, 1, 2), were synthesized from the corresponding (chloromethyl)silanes 1 , 6 a – c , and 9 a – c by treatment with potassium acetate under phase‐transfer‐catalysis conditions. These compounds were found to provide 2,2,5,5‐organo‐substituted 1,4‐dioxa‐2,5‐disilacyclohexanes 3 , 8 a – c , and 11 a – c if treated with organotin(IV) catalysts such as dioctyltin oxide. The reaction proceeds through transesterification of the acetoxy and alkoxy units followed by ring‐closure to form a dimeric six‐membered ring. The corresponding alkyl acetates are formed as the reaction by‐products. With these mild conditions, the method overcomes the drawbacks of previously reported synthetic routes to furnish 2,2,5,5‐tetramethyl‐1,4‐dioxa‐2,5‐disilacyclohexane ( 3 ) and even allows the synthesis of 1,4‐dioxa‐2,5‐disilacyclohexanes bearing hydrolytically labile alkoxy substituents at the silicon atom in good yields and high purity. These new materials were fully characterized by NMR spectroscopy, elemental analysis, mass spectrometry, and X‐ray analysis (trans‐ 8 a ).     

NaF含量对以水滑石结构为前驱体的固体碱催化剂F-Ca-Mg-Al及碳酸二甲酯合成的影响（英文）

以碳酸丙烯(PC)和甲醇为原料,经酯交换反应合成的多功能、环保的碳酸二甲酯(DMC)是一种绿色、节能的合成方法。CaO固体碱催化剂对该反应具有良好的催化性能,但其再生性不理想。以F-Ca-Mg-Al水滑石(LDHs)为原料,制备了一系列不同Na F用量的固体碱催化剂,并对其进行了表征和酯交换反应测试。与不加氟的FCMA-0催化剂相比,经氟改性后的催化剂的比表面积、碱量、催化活性等性能均有明显提高。催化活性由高到低依次为:FCMA-0.8> FCMA-0.4>FCMA-1.2> FCMA-1.6> FCMA-0,这与总碱位量和强碱位量一致。FCMA-0.8催化剂活性最好,与纯CaO催化剂的相当,PC转化率为66.8%,DMC选择性为97.4%,DMC收率为65.1%。在10次循环使用后,FCMA-0.8催化剂的DMC收率仅下降3.9%(CaO催化剂下降33.2%)。FCMA-0.8在PC与甲醇酯交换制DMC方面具有良好的工业应用前景。     

Metal- and Solvent-Free Transesterification and Aldol Condensation Reactions by a Homogenous Recyclable Basic Ionic Liquid Based on the 1,3,5-Triazine Framework

A new recyclable basic ionic liquid was introduced as an efficient catalyst for aldol condensation and transesterification reactions under environmentally friendly conditions. The catalyst was prepared based on methyl imidazolium moieties bearing hydroxide counter anions via the Hofmann elimination on a 1,3,5-triazine framework. The ionic liquid with two functionalities including anion stabilizer and high basicity, was used as an efficient catalyst for aldol condensation as well as transesterification reaction of a variety of alkyl benzoates. All reactions were performed in the absence of any external reagent, co-catalyst, or solvent, in line with environmental protection. The kinetics isotope effect (KIE) was conducted for the transesterification reaction to elucidate the mechanism and rate determining step (RDS). It worth noted that, the homogeneous catalyst could be recycled from the reaction mixture and reused for several consecutive runs with insignificant drop of basicity and conversion.     

Immobilization of Eversa® Transform via CLEA Technology Converts It in a Suitable Biocatalyst for Biolubricant Production Using Waste Cooking Oil

The performance of the previously optimized magnetic cross-linked enzyme aggregate of Eversa (Eversa-mCLEA) in the enzymatic synthesis of biolubricants by transesterification of waste cooking oil (WCO) with different alcohols has been evaluated. Eversa-mCLEA showed good activities using these alcohols, reaching a transesterification activity with isoamyl alcohol around 10-fold higher than with methanol. Yields of isoamyl fatty acid ester synthesis were similar using WCO or refined oil, confirming that this biocatalyst could be utilized to transform this residue into a valuable product. The effects of WCO/isoamyl alcohol molar ratio and enzyme load on the synthesis of biolubricant were also investigated. A maximum yield of around 90 wt.% was reached after 72 h of reaction using an enzyme load of 12 esterification units/g oil and a WCO/alcohol molar ratio of 1:6 in a solvent-free system. At the same conditions, the liquid Eversa yielded a maximum ester yield of only 34%. This study demonstrated the great changes in the enzyme properties that can be derived from a proper immobilization system. Moreover, it also shows the potential of WCO as a feedstock for the production of isoamyl fatty acid esters, which are potential candidates as biolubricants.     

Miscibility of poly(ethylene terephthalate)/poly(ethylene 2,6-naphthalate) blends by transesterification

The effects of transesterification on the miscibility of poly(ethylene terephthalate)/poly(ethylene 2,6-naphthalate) were studied. Blends were obtained by solution precipitation at room temperature to avoid transesterification during blend preparation. The physical blends and transesterified products were analyzed by wide-angle x-ray scattering, differential scanning calorimetry, and nuclear magnetic resonance spectroscopy. It was found that the physical blends are immiscible and when the extent of transesterification reaches 50% of the completely randomized state, independent of blend composition, the blends are not crystallizable and show a single glass transition temperature between those of starting polymers. The interchange reactions were significantly influenced by annealing temperature and time but negligibly by blend composition. © 1996 John Wiley & Sons, Inc.     

苯乙酮酸薄荷醇酯的合成及其不对称Henry反应

在四乙氧基钛催化下,用天然丰产的薄荷醇为手性源与非手性苯乙酮酸乙酯进行酯交换得到含手性基团的苯乙酮酸薄荷醇酯,经手性基团的立体选择性控制让其与硝基甲烷缩合,主要得到2s-2-羟基-2-苯基-3-硝基丙酸薄荷醇酯,用IR、1H NMR、13C NMR确认了合成物结构。并用高效液相色谱法分析了诱导不对称Henry缩合反应效果。     

环戊二烯掺杂乙烷桥联有序介孔材料的制备、表征及应用

 以单硅酯 (2-(环戊基-1,3-二烯基) 乙基) 三乙氧基硅烷 (TEECp) 和含有亚乙基桥键的硅酯 1,2-二 (三乙氧基硅基) 乙烷为硅源, 以三嵌段共聚物 P123 为模板剂, 通过调节 TEECp 预水解时间, 采用共聚法合成了环戊二烯掺杂乙烷桥联材料 (Cp-PMO), 并采用小角 X 射线衍射、N2 物理吸附、透射电镜、红外光谱和热重等技术对样品进行了表征. 结果表明, 环戊二烯基被成功引入到乙烷桥联材料中, 所得 Cp-PMO 样品具有高度有序的二维六方介孔孔道, 热稳定性较高; 随着材料中环戊二烯含量的增加, 其有序性降低, 孔径、比表面积和孔体积均有所减小, 孔壁逐渐增厚. 在乙酸乙酯与正丁醇的酯交换反应中, Cp-PMO 样品表现出较高的催化活性. 当该样品中环戊二烯含量为 30% 时, 乙酸乙酯转化率和乙酸丁酯收率分别可达 19.3% 和 10.6%.     

新型碱性离子液体催化酯交换合成生物柴油

两步法合成了吗啉阴离子型碱性离子液体1-丁基-3-甲基吗啉盐Im,经 ¹H-NMR和FT-IR分析确认了离子液体中间体的结构,并通过阴离子交换得到碱性离子液体,对该离子液体在酯交换制备生物柴油反应中的催化性能进行了研究。结果表明,该碱性离子液体Im具有较高的酯交换催化活性,在60 ℃、催化剂用量为3%、醇油物质的量比为6.5：1.0、反应2 h的条件下,产物脂肪酸甲酯（FAME）含量可达95.80%。而且该离子液体的催化稳定性较好,重复使用5次后仍有较高的催化活性。     

纳米SO42-/ZrO2的合成及其在酯交换反应中的催化性能

采用两步晶化-后浸渍法合成了纳米SO₄^2-/ZrO₂固体酸催化剂,并考察了其在植物油与甲醇酯交换反应中的催化性能。XRD、N₂吸附-脱附和TEM等结果表明,经过600℃焙烧,催化剂仍保持单一四方相,粒径大小为5~10 nm,比表面积为137 m²·g^-1,孔径为3.6 nm。NH₃-TPD结果表明,随着焙烧温度升高,催化剂表面的酸含量和酸强度逐渐增加,超强酸含量的增加,更有利于反应在温和条件下进行。在酯交换反应中,当醇油物质的量之比为20：1,反应温度为135℃,反应时间为6 h,600℃焙烧后催化剂用量为5%（w/w）时,植物油能够完全转化为脂肪酸甲酯。与传统的SO₄^2-/ZrO₂催化剂相比,该催化剂在低温反应条件下具有更高的催化性能和良好的重复使用性。     

Rare earth‐doped calcium‐based magnetic catalysts for transesterification of glycerol to glycerol carbonate

Several rare earth‐doped, calcium‐based magnetic catalysts were prepared for the synthesis of glycerol carbonate. The basicity and basic strength analysis of the catalysts showed that the doping of rare earth improved the basicity of the catalysts, and the doping of lanthanum maximized it. In addition, with the doping of lanthanum, the particle size of the catalyst became smaller to promote the organic reactants near the active sites of catalysts, thereby effectively improving the performance. NiFe₂O₄@[CaO‐La₂O₃] shows better catalytic performance with 99.0% yield of glycerol carbonate compared to the other catalysts. The NiFe₂O₄@(CaO‐La₂O₃) could be reused in six cycles without significant loss in activity.