Niobium (V) chloride catalyzed Knoevenagel condensation: An efficient protocol for the preparation of electrophilic alkenes

The condensation reaction has been carryout very conveniently to obtain the corresponding substituted olefins in excellent yields and showing all the products in excellent E-geometry. The reaction conditions are very mild and applicable to various aldehydes as well as active methylene compounds.     

Mn-MOF@Pi composite: synthesis,characterisation and an efficient catalyst for the Knoevenagel condensation reaction

We have synthesised new Mn-MOF@Pi composite by encapsulation of piperidine in desolvated Mn-MOF and investigated its catalytic performance in Knoevenagel condensation reaction. The newly developed composite is compatible with various aromatic aldehydes and converting them to the desired Knoevenagel condensation products in good yields and selectivity. Furthermore, composite Mn-MOF@Pi is reusable and shows good catalytic activity than native MOF.     

氨基化磁性Fe3O4@Cu3(BTC)2材料的合成及其在Knoevenagel缩合中的催化性能

金属有机骨架材料具有大比表面积、高孔隙率、热稳定性好、规整且可调控的孔结构、易于功能化的骨架金属离子和有机配体等优点,是制备多相催化剂的重要材料之一.虽然减小金属有机骨架材料等多孔材料的粒径可以提高反应物的传质效率,从而提高其催化活性;但是,纳米尺寸催化剂的分离和回收困难.将磁性纳米粒子和金属有机骨架材料结合制备具有核-壳结构的磁性金属有机骨架材料是解决上述问题的有效方法.此类材料兼具磁性材料和金属有机骨架材料的双重优势,既可以磁性分离,又具有金属有机骨架材料的催化活性.而且,厚度可控的壳层材料表现出与纳米催化剂相当甚至更好的催化活性.我们采用逐层自组装方法制备了核-壳结构的磁性Fe3O4@Cu3(BTC)2复合材料,并对材料进行氨基化修饰,制备了基于金属有机骨架材料的磁性多相碱催化剂.采用粉末X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、透射电镜(TEM)、扫描电镜(SEM)、氮气吸附等方法对材料的组成和结构进行了表征,并考察了材料在Knoevenagel缩合反应中的催化性能.首先采用粉末XRD表征材料的晶体结构.在复合材料Fe3O4@Cu3(BTC)2的XRD谱中,同时出现了Fe3O4和Cu3(BTC)2的特征衍射峰.采用氨基配体修饰后,材料的XRD谱没有明显变化,说明修饰后的材料保持了Fe3O4@Cu3(BTC)2的晶体结构.透射电镜结果表明,包裹25次得到的磁性复合材料Fe3O4@Cu3(BTC)2是以Fe3O4为核心,以Cu3(BTC)2为壳的核-壳结构,壳层厚度大约为200 nm.氨基修饰后,材料的透射电镜图相对修饰前无明显变化.扫描电镜结果表明,合成的Fe3O4为球形结构,粒径为100-600 nm.采用Cu3(BTC)2进行包裹后,在Fe3O4表面生长了由Cu3(BTC)2纳米颗粒组成的壳层.采用氨基配体修饰后,材料的形貌无明显改变.进一步采用氮气吸附表征材料的孔结构并测定材料的比表面积和孔体积.结果表明,由于大比表面的Cu3(BTC)2的引入,复合材料Fe3O4@Cu3(BTC)2的比表面积增大为462 m2/g,孔体积为0.38 cm3/g.氨基修饰后,材料的比表面积和孔体积都有较大程度的降低,说明配体分子占据了壳层材料Cu3(BTC)2中的纳米孔道.采用苯甲醛和氰基乙酸乙酯的Knoevenagel缩合反应作为模型,考察了材料的催化活性.研究发现,Fe3O4对此反应几乎没有活性,Fe3O4@Cu3(BTC)2给出了中等的催化活性.在材料上引入氨基后,由于氨基和Cu3(BTC)2上的Lewis酸性位点的协同效应,在很大程度了提高了材料的催化活性.溶剂效应实验结果表明,反应溶剂对材料的活性和选择性具有较大影响,极性或质子性溶剂有利于反应的进行.多相催化剂的循环稳定性是其重要评价指标之一.热过滤实验结果表明,滤液中无催化活性,反应中的催化活性来源于固体材料,此催化反应为多相催化.随后考察了材料的循环稳定性.虽然氨基化Fe3O4@Cu3(BTC)2材料在溶剂DMSO中表现出最高的催化活性,但XRD和电镜表征结果表明,材料在DMSO中结构遭到破坏,因此循环过程中催化剂的活性损失严重.然后考察了氨基化材料在乙醇中的循环稳定性,发现材料在乙醇中表现出较好的循环稳定性.通过简单磁性分离进行催化剂的分离和回收,催化剂循环使用3次而没有明显的活力损失.而且,XRD和电镜表征结果显示,催化剂的结构在反应过程中没有遭到明显破坏.     

Synthesis of a new urea derivative: a dual-functional organocatalyst for Knoevenagel condensation in water

A phenylalanine–urea compound-catalyzed Knoevenagel condensation in water is reported. Various aldehydes and active methylene compounds undergo condensation at room temperature to give the desired products in high yields. The mechanism of the condensation of aldehydes with Meldrum’s acid catalyzed by the novel urea derivative is also disclosed.     

Solid phase synthesis of substituted quinolin-2(1H)-one-3-carboxylic acids via an intramolecular Knoevenagel condensation

A solid phase synthesis of substituted quinolin-2(1H)-one-3-carboxylic acids is described. The products are formed in a two-step synthesis in which ortho-aminophenones are first coupled to malonic acid bound to the Wang Resin followed by ring closure via an intramolecular Knoevenagel condensation.     

An efficient method for Knoevenagel condensation: a facile synthesis of 5-arylidenyl 2,4-thiazolidinedione

Abstract

Knoevenagel condensation of various aromatic aldehydes with 2,4-thiazolidinedione has been carried out in polyethylene glycol-300. The reactions were carried out at moderate temperature with very simple isolation procedure and with better yields.     

功能化SBA-15的合成、表征及其在Knoevenagel缩合反应中溶剂效应的研究

利用后接枝法合成了含有N-丙基苄胺、N-丙基邻羟基苄胺、N-丙基对羟基苄胺功能化的SBA-15,通过傅里叶红外、X射线衍射、N2-吸附脱附、元素分析对功能化SBA-15的表征表明,功能化的SBA-15保持了规整有序的介孔孔道;同时考察了3种功能化SBA-15对Knoevenagel缩合反应的催化性能,结果表明,三种催化剂都具有较高的催化活性,在以乙醇为溶剂,50℃反应6h的条件下,苯甲醛和氰乙酸乙酯的反应产率均达到80%左右,在该反应体系中有明显的溶剂化效应,质子化溶剂更有利于Knoevenagel缩合反应的进行.     

离子液体[2-aemim]im催化Knoevenagel反应和异噁唑酮合成

以碱性离子液体1-(2-氨基乙基)-3-甲基咪唑咪唑盐([2-aemim]im)作为催化剂,催化Knoevenagel反应和4-芳亚甲基异噁唑-5(4H)-酮衍生物的合成。实验结果表明:在无溶剂条件下,该离子液体对Knoevenagel反应具有很高的催化活性,一系列芳香醛和活泼亚甲基化合物的反应在室温条件下2 min内顺利完成,均以90%以上的高产率生成取代烯烃产物.将该碱性离子液体用于催化乙酰乙酸乙酯或苯甲酰乙酸乙酯、盐酸羟胺和芳香醛三组分一锅法缩合制备4-芳亚甲基异噁唑-5(4H)-酮衍生物,具有反应时间较短、产率较高和后处理简单的特点。离子液体经简单处理后能多次循环使用。     

Three-component condensation in the synthesis of 4-(2-chlorophenyl)-3-cyano-5-ethoxycarbonyl-6-propyl-3,4-dihydropyridine-2(1H)-thione

Condensation of 2-chlorobenzaldehyde with cyanothioacetamide and ethyl butyroylacetate results in 4-(2-chlorophenyl)-3-cyano-5-ethoxycarbonyl-6-propyl-3,4-dihydropyridine-2(1H)-thione, whose further transformation affords the corresponding substituted 2-methylthio-1,4-dihydropyridine. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 173–175, January, 2000.     

3-[N-(4-甲基苯基)氨基羰基]-5-[4-(4-甲酸基苯甲氧基)苯亚甲基]-2,4-噻唑烷二酮的合成

以对甲苯胺和对甲基苯甲酸甲酯为起始原料,经NBS溴化、亲核取代、酸水解和Knoevenagel缩合等6步反应合成了抗细菌生物膜化合物—3-[N-(4-甲基苯基)氨基羰基]-5-[4-(4-甲酸基苯甲氧基)苯亚甲基]-2,4-噻唑烷二酮,总收率57.3％,其结构经1H NMR,ESI-MS和元素分析确证.     

Novel,Efficient, and Green Procedure for the Knoevenagel Condensation Catalyzed by Diammonium Hydrogen Phosphate in Water

Knoevenagel condensation of various aromatic and heteroaromatic aldehydes with active methylene compounds like methyl and ethyl cyanoacetate, malononitrile, and cyanoacetamide proceeds smoothly with stirring in water in the presence of 4 mol% of diammonium hydrogen phosphate. The reactions were carried out at room temperature in short periods with very simple workup procedure and good to high yields.     

Three-component condensation in the synthesis of 4-(2-chlorophenyl)-3-cyano-5-ethoxycarbonyl-6-propyl-3,4-dihydropyridine-2(1H)-thione

Condensation of 2-chlorobenzaldehyde with cyanothioacetamide and ethyl butyroylacetate results in 4-(2-chlorophenyl)-3-cyano-5-ethoxycarbonyl-6-propyl-3,4-dihydropyridine-2(1H)-thione, whose further transformation affords the corresponding substituted 2-methylthio-1,4-dihydropyridine. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 173–175, January, 2000.     

Polyvinyl amine as a modified and grafted shell for Fe3O4 nanoparticles: As a strong solid base catalyst for the synthesis of various dihydropyrano[2,3-c]pyrazole derivatives and the Knoevenagel condensation

In this work, we reported one-step deposition of polyacrylamide on nano-magnetite surface via a simple and in situ polymerization of acryl amide to form n-Fe₃O₄/PAM nanocomposite. The amide (–CONH₂) groups could be converted easily to amine (–NH₂) groups through Hofmann degradation to introduce n-Fe₃O₄/PVAm as a highly efficient heterogeneous base catalyst. The obtained organic-inorganic nanocomposite exhibited high catalytic activity for the solvent-free syntheses of various dihydropyrano[2,3-c]pyrazole derivatives and the Knoevenagel condensation in high to excellent yields and in the following, a plausible mechanism for the synthesis of them has been proposed. Because of the polymer layer coated Fe₃O₄ nanoparticles, the catalyst has many catalytic units, and acceptable thermal stability and recyclability. Titration, FT-IR, SEM, TGA, VSM, and XRD analysis were used for characterization of the catalyst. Also, the nanocomposite can be easily recovered by a magnetic field and reused up to 9 times without distinct deterioration in catalytic activity.     

One-pot synthesis of quinolin-2-(1H)-ones via tandem Ugi-Knoevenagel condensations

A new application of the Ugi reaction in the synthesis of heterocyclic compounds is described. Substituted quinolin-2-(1H)-ones are formed in one-pot sequential Ugi four-component condensation and intramolecular Knoevenagel cyclization between o-acylanilines, aldehydes, malonic or tosylacetic acids and cyclohexyl isocyanide.     

An expedient synthesis of 3-alkylideneoxindoles by Ti(OPr)4/pyridine-mediated Knoevenagel condensation

3-Alkylideneoxindoles have been prepared in excellent yields from oxindole and carbonyl compounds via an in situ generated titanium enolate of oxindole. (Z)-3-Alkylideneoxindoles could be synthesized selectively as major products from unsymmetrical ketones.     

Novel capto-dative (Z,E)-2-(alkylthio)alk-2-en-4-ynals: synthesis and heterocyclization

An efficient synthesis of new (Z,E)-2-(alkylthio)alk-2-en-4-ynals by aldol condensation reaction of ynals with (alkylthio)-acetaldehydes using NaOH/DMF system has been developed.The reaction of these products with N,N-diphenylethylene-diamine and p-tosylmethyl isocyanide proceeds at the carbonyl group to form the corresponding imidazolidine and oxazole derivatives.     

A Simple,Efficient and Green Procedure for Knoevenagel Condensation in Water or under Solvent‐free Conditions

1,4‐Diazabicyclo[2.2.2]octane was used as an efficient catalyst in the Knoevenagel condensation reaction of various kinds of aromatic/aliphatic/heterocyclic/αβ‐unsaturated aldehydes and ketones with active methylene compounds. This is a convenient and rapid method for Knoevenagel condensation, which affords the corresponding substituted electrophilic alkenes in excellent yields. The reaction condition is mild and the method is operationally simple. The products, only E‐isomers were detected, did not need to be purified. The use of water as the reaction medium makes the process environmentally benign. The catalysts can be recycled six times without activity loss.     

Nanocrystalline ZnO for Knoevenagel Condensation and Reduction of the Carbon,Carbon Double Bond in Conjugated Alkenes

A novel efficient and eco‐friendly nanocrystalline ZnO catalyst was used for the Knoevenagel condensation and for the reduction of C?C double bonds at room temperature in the absence of solvents.