Aldol Condensation of Acetylferrocene under Ultrasound

Aldol condensation of acetylferrocene with aromatic aldehydes afforded ferroceny- lenones in 76%-92% yields under ultrasound at room temperature.

Geometric effect promoted hydrotalcites catalysts towards aldol condensation reaction

In solid basic catalysis field,how to achieve optimized activity and desired stability through elaborate control over basic site properties remains a challenge.In this work,taking advantage of the structure memory effect of layered double hydroxides(LDHs),rehydrated Ca4 Al1-x Gax-LDHs and Ca4 Al1-x Inx-LDHs catalysts were prepared and applied in aldol condensation reaction that isobutyraldehyde(IBD)reacts with formaldehyde(FA)to obtain hydroxypivalaldehyde(HPA).Notably,the resulting re-Ca4 Al0.90Ga0.10-LDHs exhibits an extraordinarily-high catalytic activity(HPA yield:72%),which is to our best knowledge the highest level in this reaction.The weak Br?nsted basic site,7-coordinated Ca-OH group,which serves as an active site,catalyzes the condensation process and promotes the product desorption.Studies on structure-property correlations demonstrate that Ga as a structural promoter induces a moderate expansion of the laminate lattice,which results in a significant increase in the concentration of weak basic sites in re-Ca4Al0.90Ga0.10-LDHs,accounting for its high catalytic activity.This work illuminates that geometric structure of basic active sites can be tuned via introducing catalyst additive,which leads to a largely improved performance of hydrotalcite solid basic catalysts towards aldol condensation reaction.

HZSM-35 zeolite catalyzed aldol condensation reaction to prepare acrylic acid and its ester:Effect of its acidic property

Acrylic acid(AA)and its ester,methyl acrylate(MA),were produced by a green one‐step aldol condensation reaction of dimethoxymethane and methyl acetate.The reaction was conducted over ZSM‐35 zeolites with different concentrations of Bronsted acid,which were prepared by the sodium ion‐exchange process with H‐form zeolite.The acidic property of HZSM‐35 was studied in detail through infrared experiments.About 51%of all bridging OH groups were distributed in cages,while 23%and 26%,respectively,were distributed in 10‐and 8‐ring channels.The catalytic performance was enhanced by a high concentration of Bronsted acid,indicating that Bronsted acid is an active site for the aldol condensation reaction.The ZSM‐35 zeolite possessing a concentration of Bronsted acid as high as 0.049 mmol/g demonstrated excellent performance with a MA+AA selectivity of up to 73%.

Highly efficient Nb2O5 catalyst for aldol condensation of biomass-derived carbonyl molecules to fuel precursors

Aldol condensation is of significant importance for the production of fuel precursors from biomass- derived chemicals and has received increasing attention. Here we report a Nb2O5 catalyst with excellent activity and stability in the aldol condensation of biomass-derived carbonyl molecules. It is found that in the aldol condensation of furfural with 4-heptanone, Nb2O5 has obviously superior activity, which is not only better than that of other common solid acid catalysts (ZrO2 and Al2O3), more importantly, but also better than that of solid base catalysts (MgO, CaO, and magnesium- aluminum hydrotalcite). The detailed characterizations by N2 sorption/desorption, NH3-TPD, Py-FTIR and DRIFTS study of acetone adsorption reveal that Nb2O5 has a strong ability to activate the C=O bond in carbonyl molecules, which helps to generate a metal enolate intermediate and undergo the nucleophilic addition to form a new C–C bond. Furthermore, the applicability of Nb2O5 to aldol condensation is extended to other biomass-derived carbonyl molecules and high yields of target fuel precursors are obtained. Finally, a multifunctional Pd/Nb2O5 catalyst is prepared and successfully used in the one-pot synthesis of liquid alkanes from biomass-derived carbonyl molecules by combining the aldol condensation with the sequential hydrodeoxygenation.

THE SOLID STATE ALDOL CONDENSATION REACTION OF ACETYLFERROCENE AND AROMATIC ALDEHYDES

The aldol condensation reactions of acetylferrocene with several aromatic aldehydes have been studied in the solid state.The results showed that they revealed different reactivities in the solid slate from that in solution and eight compounds have been prepared. Their structures have been characterized by UV,IR,1~HNMR,HS and elemental analysis.

Study on Aldol Condensation of HCHO and CH_3CHO over MgO Catalysts Modified by Lanthanum and Cerium

Aldol condensation of HCHO and CH_3CHO over MgO, modified MgO and Al_2O_3 with rare earth oxides, was studied. The measurement of adsorption of pyrrole on catalysts by in-situ FT-IR and NH_3 TPD indicated that the addition of elements La or Ce into MgO increased the acidity of the solid. In-situ FT-IR showed that the activation of-C=O in HCHO adsorbed on CeO-MgO and La_2O_3-MgO occurred. The measurement of catalytic activity implied that the modified catalysts can promote the formation of pentaerythritol, dipentaerthritol and tripentaerythritol.

Functioned Calix[4]arenes as Artificial Enzymes Catalyze Aldol Condensation

Aldolase models derived from calix[4]arene were designed and synthesized. The aldol condensation of p-nitrobenzaldehyde with acetone was catalyzed by the synthetic enzymes proceeded under mild conditions to offer chiefly aldol-type product in good yield.

InCl_3·4H_2O Catalyzed Aldol Condensation of Cycloalkanones with Aromatic Aldehydes

InCl34H2O catalyzes the cross-aldol condensation of cycloalkanones with aromatic aldehydes in sealed tube under solvent free condition to afford an efficient method for the synthesis of a, a-bis(substituted)benzylidenecycloalkanones.

Intramolecular Aldol Condensation ofα- Oxo Ketene Dibenzylthioacetals: A Facile Route to Substituted Thiophenes

A new method for the synthesis of substituted thiophenes was through intramolecular aldol condensation ofα-oxo ketene dibenzylthioacetals.All products were confirmed with IR, 1 H NMR and elemental analysis.

Kinetics of Aldol Condensation of Furfural with Acetone Catalyzed by 1,8-Diazabicyclo[5.4.0]undec-7-ene

The kinetics of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed aldol condensation of furfural with acetone was investigated under free solvent conditions from 50℃ - 90℃. The highest yield of 1,4-pentandien-3-on-1,5-di-furanyl catalyzed by DBU reached 98.0% under optimized conditions. According to the kinetic analysis, the reaction order of furfural was estimated as 1.0, the apparent activation energy was 17.7 kJ.mol.1, and the pre-exponential factor was 2.67 L.min.1 in fitting with the Arrhenius equation, which explains the high efficiency of the DBU catalyst. DBU-catalyzed aldol condensation with free solvent offers an alternative route to simplify aldol condensation and separation into a single step.

FUNCTIONALIZED CYCLODEXSTRINS BEARING AM INOALKYLIMINO GROUPS AS ACTIVE CENTERS TO CATALYZE ALDOL CONDENSATIONS

Efficient catalysis of functinnatized β-cyctodextrins bearing aninoatkytimino groups for atdot condensations of nitrobenzatdehydes and acetone has been effected and substantiated by preparative experiments

Cooperative catalytic effects between the penta-coordinated Al and Al_(2)O_(3)in Al_(2)O_(3)-AlPO_(4)for aldol condensation of methyl acetate with formaldehyde to methyl acrylate

The bare amorphous Al_(2)O_(3)-AlPO_(4)and Cs/Al_(2)O_(3)-AlPO_(4)catalysts were developed for the aldol condensation of methyl acetate with formaldehyde to methyl acrylate.The structure and property of catalyst were characterized by XRD,XPS,BET,Pyridine-IR,FT-IR,^(27)Al-MASNMR,NH_(3)-/CO_(2)-TPD and SEM.The correlation between structural features and acid-base properties was established,and the loading effect of the cesium species was investigated.Due to cooperative catalytic effects between the penta-coordinated Al and Al_(2)O_(3),the weak-Ⅱacid and medium acid site densities and the product selectivity were improved.While the basic site densities of these catalysts were almost in proportion to the conversion of methyl acetate.The loaded Cs could form new basic sites and change the distribution of acid sites which further enhance the catalytic performance.As a result,the 10Cs/8AlP was proved to be an optimal catalyst with the yield and selectivity of 21.2%and 85%for methyl acrylate respectively.During the reaction,a deactivation behavior was observed on 10Cs/8AlP catalyst due to the carbon deposition,however,it could be regenerated by thermal treatment in the air atmosphere at 400℃.

固体超强碱催化环戊酮的Self-Aldol Condensation反应研究

2-环亚戊基环戊酮是一种重要的香料中间体,本文以环戊酮为原料,固体超强碱为催化剂,分别选用环己烷、苯、石油醚为带水剂,通过Aldol自缩合反应合成了环戊酮的二聚体2-环亚戊基环戊酮。考察了催化剂用量、带水剂种类、反应时间对环戊酮二聚体2-环亚戊基环戊酮收率的影响,最终确定最佳实验方案:环己烷为带水剂,催化剂用量为环戊酮质量的13 wt%,反应时间8小时,最佳条件下2-环亚戊基环戊酮收率可达90.8%。

α,β-Dehydroamino Acid Synthesis through Proline-Catalyzed Aldol Condensation with a Glycine Schiff Base

A general protocol for the synthesis ofα,β-dehydroamino acids and their peptides was developed.Proline efficiently catalyzed an aldol condensation reaction of a glycine Schiff base with a variety of aldehydes.The hydroxy group on the benzophenone imine was crucial for high Z/E selectivity and further transimination for protecting group-freeα,β-dehydroamino esters.Peptide elongation of both the C-and N-terminals highlighted the usefulness of our present protocol.

Efficient Synthesis of Dicycloalkenopyridines:One-pot Multicomponent Condensation of Aldehydes with Cyclic Ketones

Under microwave irradiation, the one-pot multicomponent condensation reaction of three moles of aromatic aldehydes with two moles of cyclic ketones having free a,a＇-methylene positions such as cyclopentanone or cyclohexanone in the presence of ammonium acetate and acetic acid afforded dicycloalkenopyridines with two a-arylidene groups in high yields. Under the similar reaction condition, the reaction of aromatic aldehydes with 1-tetralone having only one a-methylene position alternatively resulted in 10-aryl-2,3：5,6-dibenzoacridines.

大学综合化学实验的设计——不对称Aldol反应、分离及测定

介绍一个涵盖手性催化合成、中压Flash色谱分离及对映异构体光学纯度测定的综合性实验。本实验以2021年诺贝尔有机化学奖获得者相关的热点为主题,以手性分子脯氨酸为催化剂,催化经典的羟醛缩合(Aldol)反应,巩固了专业知识的理解与掌握,同时学会了中压Flash色谱仪进行快速纯化的原理与操作方法,了解中压Flash色谱在有机物混合物分离中的重要作用。最后利用旋光仪检测反应产物的光学纯度(op)值。结合资料的查找与阅读,探讨手性催化原理,理解催化过程形成的椅式构象过渡态决定了产物中手性碳原子构型的原因,加深了学生对有机化学基础理论的理解,提升了学生的探究能力和创新意识。

无溶剂NH_2SO_3H催化下超声促进环酮与芳香醛的Aldol缩合

以NH_2SO_3H作催化剂,在无溶剂条件下用超声技术合成了一系列α,α'-双亚苄基环酮衍生物,反应在15～45min内完成,产率76%～92%,后处理简便,且对环境友好.

新型磷酸二氢铝镓金属无机骨架结构的合成及其催化乙醛制备丁醇醛的研究

通过水热法制备了一种新型磷酸二氢铝镓(GAHPO)金属无机骨架结构,并通过单晶XRD、粉末XRD、红外,以及TG-DSC等分析手段对其进行充分表征。单晶XRD解析表明,该晶体属于三方晶系、Rc3空间群。Al(Ga)O_(6)八面体与PO_(4)四面体结构交替连接形成一维链状金属骨架,并由氢键堆叠成三维金属无机骨架结构。TG-DSC分析显示,GAHPO热稳定性良好,初始分解温度达到240℃。相比磷酸铝,Ga^(3+)的引入使磷酸铝晶格畸变,削弱了Al—O的强度,增大了Al—O键长,使更多酸性位点暴露,从而提高GAHPO的催化活性。实验结果表明,反应温度在60℃,催化剂用量为10%时,GAHPO催化乙醛缩合制备丁醇醛具有良好的转化率(47%)和优异的选择性(>99%)。酸/碱中和催化剂、NH_(3)-TPD,以及大位阻基团取代乙醛反应位点的实验验证了GAHPO的催化乙醛缩合的反应机理。本工作为新型铝基无机骨架结构及其催化应用提供了可行途径。

Cs/SiO_(2)催化合成MMA工艺及宏观动力学研究

采用浸渍法制备了不同Cs质量分数的Cs/SiO_(2)催化剂,并利用XRD､氮气物理吸附､CO_(2)-TPD和NH3-TPD等技术对其进行表征。在固定床反应器中,优化了Cs/SiO_(2)催化丙酸甲酯与甲醛缩合制备甲基丙烯酸甲酯(MMA)的反应条件,并初步进行了动力学分析。结果表明,Cs质量分数为10%的Cs/SiO_(2)催化剂性能最优,在反应温度为370℃､反应空速为1.2 h^(-1)､酯醛摩尔比为1∶1的优化条件下,丙酸甲酯的转化率为46.3%,MMA的选择性接近100%。动力学分析显示丙酸甲酯与甲醛缩合制备MMA的表观活化能为39.1 kJ/mol,非常接近理论值。

无溶剂条件下硅胶固载硫酸催化酮与芳香醛的Cross-Aldol缩合反应

在无溶剂条件下,用硅胶(mSiO2·nH2O)固载硫酸催化环己酮与芳香醛的Cross-Aldol缩合反应.结果表明,反应时间60～150 min,产率可达72%～93%,共得到5个相应的α,β-不饱和羰基化合物.该方法操作简单,催化剂可重复使用,且对环境友好.