活性炭负载壳聚糖催化室温无溶剂Knoevenagel缩合反应

通过活性炭(AC)负载壳聚糖(CS)的方法,制备了负载型的"壳聚糖/活性炭"催化剂(CS/AC)。利用FT-IR、XRD、TG-DTG、SEM、BET、元素分析等方法对催化剂进行表征,并系统研究了该催化剂在Knoevenagel缩合反应中的催化性能。结果表明,催化剂具有较好的活性,在室温无溶剂条件下,可以催化一系列芳香醛化合物与活泼亚甲基化合物进行缩合反应,产率均在80%以上;且反应体系放大100倍时,仍然保持较高的催化效率;此外,该催化剂具有较好稳定性,重复使用8次后,仍然保持较高的催化活性。     

Microwave-assisted Knoevenagel condensation in aqueous over triazine-based microporous network

A high nitrogen-containing triazine-based microporous polymeric (TMP) network was used as an efficient metal-free catalyst for Knoevenagel condensation of ethylcyanoacetate with aromatic aldehydes. The reactions were performed in water as an environmentally benign medium, under microwave irradiation within a short reaction time of 10 min. The conversions of substituted aromatic aldehydes and selectivities for Knoevenagel products were found to be in the ranges of 44–99 and 65–99 %, respectively. The electron-withdrawing substituent showed higher conversion and selectivity as compared to electron-donating substituents. The TMP network can be readily recovered and reused up to three runs without loss in catalytic activity and selectivity.     

DABCO离子液体催化Knoevenagel缩合反应

以三乙烯二胺(DABCO)为原料,通过两步法制备了离子液体[DABCO-PDO][PF6];将其用于催化芳香醛与多种活性亚甲基化合物(丙二腈,氰基乙酸乙酯,苯并噻唑乙腈,苯乙腈)的Knoevenagel缩合反应;讨论了可能的反应机理,并基于催化剂的双重催化作用阐述了反应的高效性.结果表明,该反应体系无需任何溶剂,在室温(25℃)下就能进行,催化剂用量小,反应时间短,收率高,反应后处理简单,反应普适性较高;且催化剂重复使用5次后仍保持很高的催化活性.     

双位点碱性离子液体对Knoevenagel缩合反应的协同催化作用

分别处于阴阳离子中具有两种碱性位点的离子液体催化剂1-(2-哌啶基-乙基)-3-甲基咪唑吗啉乙基磺酸盐([Pemim]-Mes)在Knoevenagel缩合反应中表现出明显的协同促进催化作用. 该催化剂在非酸性条件下循环使用10次以后仍保持良好的活性和稳定性,并普遍适用于芳香醛类底物的缩合反应. 根据实验结果,提出了紧密结合的碱性阴阳离子对协同催化Knoevenagel缩合的反应机理.     

“On-water” synthesis of 3-substituted indoles via Knoevenagel/Michael addition sequence catalyzed by Cu doped ZnS NPs

Cu doped ZnS NPs represent a green catalyst for an ‘on-water’ one-pot rapid synthesis of 3-substituted indole derivatives via Knoevenagel/Michael addition reaction of indane-1,3-dione, aromatic aldehydes, and indole. The catalytic activity of Cu doped ZnS NPs was about sevenfold higher as compared to the ZnS NPs. The Cu doped ZnS NPs catalyst could be recovered and reused for five reaction cycles, giving a total TOF = 201 h⁻¹.     

DABCO‐Catalyzed Efficient Synthesis of Naphthopyran Derivatives via One‐Pot Three‐Component Condensation Reaction at Room Temperature

Diazabicyclo[2.2.2]octane (DABCO) has been used as a mild and efficient catalyst for synthesis of 2‐amino‐3‐cyano naphthopyran derivatives via a one‐pot three‐component reaction of aromatic aldehydes, naphthols, and malononitrile at room temperature. The short reaction times, easy workup, good to excellent yields, and mild reaction conditions make this domino Knoevenagel–Michael reaction both practical and attractive.     

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.     

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.     

Fe3O4–cysteamine hydrochloride magnetic nanoparticles: New,efficient and recoverable nanocatalyst for Knoevenagel condensation reaction

Fe₃O₄ magnetic nanoparticles (MNPs) were obtained using a reduction–precipitation method. These MNPs were modified with cysteamine hydrochloride. This catalyst was characterized using a number of physicochemical measurements. The Fe₃O₄–cysteamine MNPs, as an efficient and heterogeneous catalyst, were successfully used for Knoevenagel condensation under mild conditions. The activity of this nanomagnetic catalyst in the Knoevenagel condensation of aromatic aldehydes and malononitrile is described. Easy preparation of the catalyst, easy work‐up procedure, excellent yields and short reaction times are some of the advantages.     

Polystyrene-supported chloroaluminate ionic liquid as a new heterogeneous Lewis acid catalyst for Knoevenagel condensation

Non-hygroscopic polystyrene-supported chloroaluminate ionic liquid was prepared from the reaction of Memfield resin with 1- methylimidazole followed by reaction with aluminum chloride.This Lewis acidic ionic liquid is environmentally friendly heterogeneous catalyst for the Knoevenagel condensation of aromatic and aliphatic aldehydes with ethyl cyanoacetate.The catalyst is stable(as a bench top catalyst) and reusable.     

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。     

Cellulose stabilized Fe3O4 and carboxylate-imidazole and Co-based MOF growth as an exceptional catalyst for the Knoevenagel reaction

In this study, Fe₃O₄ nanoparticles were functionalized with cellulose, and then hybridized with cobalt (II)-based metal-organic framework (Co-MOF) containing carboxylate and imidazole functionalities. FTIR, XRD, FE-SEM, TEM, BET, EDX, VSM and STA analyses were used to characterize the synthesized samples. The resultant Fe₃O₄/cellulose/Co-MOF nanocomposite was applied efficiently as a powerful and economic heterogeneous catalyst in the condensation of a variety of different aromatic aldehydes with malononitrile under solvent-free conditions at room temperature for 10 min and offered the corresponding coupling products in high yields. The catalyst could be straightforwardly separated by a magnet from the reaction mixture and reused without a noteworthy drop in catalytic activity at least five times. The use of Fe₃O₄/cellulose/Co-MOF catalyst outcomes under mild reaction conditions in very short reaction time, outstanding catalytic activity, high recyclability and an easy work-up process for Knoevenagel condensation.     

Highly efficient and chemoselective acetalization of carbonyl compounds catalyzed by new and reusable zirconyl triflate,ZrO(OTf)2

Various types of aromatic aldehydes were efficiently converted to their corresponding 1,3‐dioxanes and 1,3‐dioxolane with 1,3‐propanediol and ethylene glycol, respectively, in the presence of catalytic amount of ZrO(OTf)₂ in acetonitrile at room temperature. The catalyst can be reused several times without loss of its catalytic activity. Very short reaction times, selective acetalization of aromatic aldehydes in the presence of aliphatic aldehydes and ketones, very mild reaction conditions, reusability of the catalyst, and easy workup are noteworthy advantages of this method. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:131–135, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20523     

Sulfonated poly(4-vinylpyridine) heteropolyacid salts:A reusable green solid catalyst for Mannich reaction

Sulfonated poly（4-vinylpyridine） heteropolyacid salts acted as a heterogeneous catalyst to effectively catalyze the one-pot synthesis of β-amino carbonyl compounds via the Mannich reaction between aromatic aldehydes, aromatic ketone, and aromatic amines. In addition, the catalyst could be easily recovered by the filtration and reused six times without significant loss of catalytic activity.     

离子液体功能化二氧化硅催化Knoevenagel反应

在100 ℃, 无外加溶剂条件下, 离子液体功能化二氧化硅催化一系列芳醛和活泼亚甲基化合物进行Knoevenagel 缩合反应, 以高产率生成相应产物. 当反应底物为水杨醛与氰基乙酸乙酯的时候, 产物为3-乙氧基羰基香豆素, 这是水杨醛和氰基乙酸乙酯缩合关环, 再发生氰基醇解的产物. 采用离子液体功能化二氧化硅作为反应催化剂, 反应后催化剂可回收再利用.     

Polyethylene glycol （PEG） as a benign solvent for Knoevenagel condensation

The Knoevenagel condensation of aromatic aldehydes with active methylene compound proceeded efficiently in polyethylene glycol at room temperature with L-proline as catalyst. The yield is high and the products had E-isomer dominantly. Polyethylene glycol containing L-proline could be recycled and reused for several times without noticeably decreasing in productivity.     

新型酸性离子液体催化的 Knoevenagel缩合反应

研究了一类新型酸性离子液体催化的Knoevenagel缩合反应, 结果表明, 该催化剂适用于一系列芳香/杂环醛与α-取代活性亚甲基化合物间的反应, 反应可在室温下进行, 反应时间短且收率良好(92% ~98%). 该反应体系操作简单, 产物易分离. 提出了可能的反应机理并对机理进行了验证. 该离子液体重复使用5次后仍具有较高的反应活性.     

Synthesis and characterization of a novel and green rod-like magnetic ZnS/CuFe2O4/agar organometallic hybrid catalyst for the synthesis of biologically-active 2-amino-tetrahydro-4H-chromene-3-carbonitrile derivatives

The magnetic biocompatible rod-like ZnS/CuFe₂O₄/agar organometallic hybrid catalyst was designed and prepared based on a natural macromolecule (agar) through a green and convenient method using inexpensive, nontoxic, and easily available substances. Then, the as-prepared catalyst was characterized by several techniques such as Fourier transform-infrared spectroscopy, energy-dispersive X-ray analysis, scanning electron microscopy image, transmission electron microscopy, vibrating sample magnetometry curve, X-ray diffraction pattern, and thermogravimetric analysis. Eventually, the catalytic application of the ZnS/CuFe₂O₄/agar nanobiocomposite was assessed in sequential Knoevenagel condensation–Michael addition reaction of dimedone, malononitrile, and different substituted aromatic aldehydes for the synthesis of 2-amino-tetrahydro-4H-chromene-3-carbonitrile derivatives. Some notable strengths of this environmentally benign catalyst include simplicity of catalyst preparation and separation, affording desired products with satisfactory yields (81%–97%) in very short reaction times (3–18 min), and with no need for complicated work-up processes. Experimental tests showed that the catalyst can be successfully reused after five sequential runs without significant reduction in its catalytic efficiency.     

Simple,Efficient, and Green Method for Synthesis of Trisubstituted Electrophilic Alkenes Using Lipase as a Biocatalyst

A simple and efficient Knoevenagel condensation method for the synthesis of trisubstituted electrophilic alkenes was developed using lipase as a biocatalyst. Knoevenagel condensation was performed using the conventional method and using lipases (Aspergillus oryzae or Rhizopus oryzae) as biocatalysts, and reaction time, reaction temperature, yield, and recyclability were compared. Using a lipase as a biocatalyst eliminated the need for bases such as piperidine and pyridine. A wide range of aromatic aldehydes and ketones readily undergo condensation with active methylene compounds. The workup procedure is also very simple, and yields of the reactions are in the range of 75% to 95%. Both the biocatalysts were effectively recycled four times with no major decrease in the yield of product. The remarkable catalytic activity and reusability of lipase widens its applicability in Knoevenagel condensation with good to excellent yields for synthesis of trisubstituted electrophilic alkenes.     

Highly efficient Knoevenagel condensation reactions catalyzed by a proline-functionalized polyacrylonitrile fiber

A new proline-functionalized fiber catalyst was employed for the first time to catalyze the Knoevenagel condensation reactions between aromatic aldehydes and ethyl cyanoacetate or malononitrile.This fiber catalyst exhibits a high efficiency(0.5-2 mol% of catalyst with yields of 90%-99%) and excellent reusability(up to 20 times) without the need for additional treatments.