Efficient Knoevenagel Condensation Research Articles

Nanoconfined superfluid for highly efficient chemical reactions

Highly efficient chemical reactions are vital for the development of green growth and sustaining industrial society, yet achieving effective flow reactions under mild conditions remains challenging. In a recent research article published in Matter, Pang and colleagues 1 Pang S. Peng D. Hao Y. Song B. Zhang X. Jiang L. Regulating interlayer spacing of aminated graphene oxide membranes for efficient flow reactions. Matter. 2023; 6: 1173-1187 Abstract Full Text Full Text PDF Scopus (1) Google Scholar achieved a nanoconfined superfluid-based chemical reaction with ∼100% conversion and reaction time of less than 29 s at 22°C using multilayer aminated graphene oxide nanoconfined membranes. These findings highlight the potential for nanoconfined membranes to revolutionize the field of chemical synthesis. Highly efficient chemical reactions are vital for the development of green growth and sustaining industrial society, yet achieving effective flow reactions under mild conditions remains challenging. In a recent research article published in Matter, Pang and colleagues 1 Pang S. Peng D. Hao Y. Song B. Zhang X. Jiang L. Regulating interlayer spacing of aminated graphene oxide membranes for efficient flow reactions. Matter. 2023; 6: 1173-1187 Abstract Full Text Full Text PDF Scopus (1) Google Scholar achieved a nanoconfined superfluid-based chemical reaction with ∼100% conversion and reaction time of less than 29 s at 22°C using multilayer aminated graphene oxide nanoconfined membranes. These findings highlight the potential for nanoconfined membranes to revolutionize the field of chemical synthesis. Regulating interlayer spacing of aminated graphene oxide membranes for efficient flow reactionsPang et al.MatterFebruary 13, 2023In BriefIt remains a challenge to achieve effective flow reactions under mild conditions. Here, we report a strategy of regulating interlayer spacing of aminated graphene oxide membranes for efficient Knoevenagel condensation. Through decreasing the interlayer spacing, a flow reaction with ∼100% conversion is achieved at 22°C with a short reaction time (<29 s). This work presents a new strategy for efficient and rapid flow reactions under mild conditions. Full-Text PDF

A new parallel, rapid, and green Knoevenagel condensation catalyzed by in-situ generated carbonic acid (CO2 (g) in water): Application to intermediate of AMG 837

This work demonstrates the first-ever use of carbonic acid from sparkling water and the one generated in-situ from dry ice for efficient Knoevenagel condensation. Various aldehydes reacted well with active methylenes in a shorter reaction time in environmentally-friendly ethanol: water (1:1) mixture as solvent at room temperature with workup by filtration or extraction. Carbonic acid is a non-toxic and inexpensive green catalyst. Carbonic acid offers easy availability and leaves no traces of catalyst in the product. The current protocol was also extended to intermediates of AMG 837, a novel GPR40 agonist. A novel post-synthesis analysis tool was used to evaluate the quality of the organic preparation based on yield, cost, safety, conditions, and ease of workup/purification, which are atom economy (AE) of 89.47%, reaction mass efficiency (RME) is 86.31%, E-factors value of 0.16 and the eco-scale score for the method is 80.0 for model reaction. The overall atom economy (AE) of 91.73%, reaction mass efficiency (RME) is 80.95%, E-factors value of 0.25, and the eco-scale score for the method is 73.95.

The Efficient Knoevenagel Condensation Promoted by Bifunctional Heterogenized Catalyst Based Chitosan-EDTA at Room Temperature

The Efficient Knoevenagel Condensation Promoted by Bifunctional Heterogenized Catalyst Based Chitosan-EDTA at Room Temperature

Green and efficient Knoevenagel condensation catalyzed by pristine Zn-MOFs of amino acid derivatives

A series of zinc-based Metal-Organic Frameworks (MOFs) have been synthesized through the reaction of Zn(II) salts with amino acid derivatives Val-X [Val = N-(4-pyridylmethyl)-l-Valine, X = Cl−, HCOO−, CH3COO−] and Ala-X [Ala = N-(4-pyridylmethyl)-l-Alanine, X = Cl−, HCOO−]. The as-synthesized pristine Zn-MOFs adopt unique hexagonal coordination structures with robust amino and carboxylate sites. These pristine Zn-MOFs served as heterogeneous catalysts in Knoevenagel condensation reactions of aldehydes containing a variety of electron-donating and withdrawing groups with malononitrile or ethyl 2-cyanoacetate. These catalysts can promote these reactions in eco-friendly water/alcohol solvent media under mild conditions. High yields were achieved for both malononitrile and cyanoacetate products with E-isomer dominating for the latter. Furthermore, these catalysts can be recycled and reused for several times without losing catalytic activity significantly.

Wet copper-slag: A new and eco-friendly catalyst for Knoevenagel condensation

This work describes a first-ever use of Wet copper-slag for efficient Knoevenagel condensation. Copper-slag is produced as a byproduct of the copper refining and smelting processes utilized as a basic catalyst in the present work. Natural Copper-slag was converted to Wet copper-slag by immersing it in water to improve the hydroxyl group and hence basicity. Various aldehyde and ketones reacted well with active methylenes in a shorter reaction time in environmentally-friendly ethanol: water (1:1) as solvent at room temperature/90 °C. The present method showed critical advantages of mild reaction conditions, wide availability, recyclability, and magnetic separability of a catalyst with higher product yields. The current protocol was also applied to synthesize the intermediate of AMG 837, a novel GPR40 agonist.

Sulfated polyborate as Bronsted acid catalyst for Knoevenagel condensation

We have developed the use of Bronsted acid for Knoevenagel condensation. Sulfated polyborate has been used for efficient Knoevenagel condensation of aromatic, heterocyclic, α,β-unsaturated, and aliphatic aldehydes in the ecologically friendly ethanol: water (1:1) mixture as solvent at 70 °C. It took less time for certain aldehydes to react with active methylenes. The present method demonstrated significant benefits in terms of first-time use of Bronsted acid catalyst, mild reaction conditions, and better product yields.

Novel and Efficient Knoevenagel Condensation over Mesoporous SBA‐15 Supported Acetate‐functionalized Basic Ionic Liquid Catalyst

AbstractA type of multifunctional mesoporous SBA‐15 supported imidazolium ionic liquids SBA‐15@IL‐OAc have been designed and synthesized, characterized and tested as heterogeneous catalysts in the Knoevenagel condensation. The prepared catalysts exhibit good catalytic performances in the reaction at room temperature, especially the supported ionic liquid SBA‐15@IL‐OAc(0.8) with excellent yields of 90∼98 %, probably due to the synergetic effect between acetate anion sites of imidazolium ionic liquid and hydroxyl active sites of SBA‐15. In addition, the recyclability of the heterogeneous catalyst was tested, and the cycle test showed that the catalyst could be reused five times without significantly reducing the catalytic activity.

Amine Functionalized Graphene Oxide Stabilized Pickering Emulsion for Highly Efficient Knoevenagel Condensation in Aqueous Medium

A Pickering emulsion catalytic system was developed using amphiphilic amine-functionalized graphene oxide (GO-NH2) for a Knoevenagel condensation in aqueous medium instead of organic solvent. The properties of GO-NH2 and the Pickering emulsion stabilized by GO-NH2 were characterized by Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), organic elemental analysis (OEA), contact angle (CA), Brunauer–Emmett–Teller surface area, and optical microscopy. The results indicated that the properties of the as-prepared Pickering emulsion system, such as droplet density, size, and distribution, were greatly affected by the amount of GO-NH2 and the oil–water ratio, which were closely related to the catalytic performance for Knoevenagel condensation reactions. Furthermore, this Pickering emulsion system for the Knoevenagel condensation in an aqueous medium exhibited a much higher catalytic activity than those of GO-NH2 in organic solvents under the same reaction conditions. The reaction rate constant (k) in the Pickering emulsion system was calculated to be 0.043 min−1 at 50 °C. The enhanced activity of the Pickering emulsion was mainly attributed to large interfaces between GO-NH2 and reactants in the emulsion, and the clear confinement effect. Furthermore, GO-NH2 remained stable for preparing Pickering emulsion systems after recycling in six runs, exhibiting its good reusability. A novel Pickering emulsion catalytic system was developed using amphiphilic amine functionalized graphene oxide (GO-NH2) for Knoevenagel condensation in aqueous medium instead of organic solvents. It exhibited excellent catalytic performance in the reaction.

Imidazole-induced self-assembly of polyoxovanadate cluster organic framework for efficient Knoevenagel condensation under mild conditions

Three new polyoxovanadates have been made, one of them displays highly efficient heterogeneous solvent-free catalytic activity and excellent recyclability in the Knoevenagel condensation at room temperature.

Efficient Knoevenagel condensation catalyzed by imidazole-based halogen-free deep eutectic solvent at room temperature

For the first time, we employed the halogen-free deep eutectic solvent (DES) into the Knoevenagel condensation between aromatic aldehydes and active methylene compounds at room temperature. The DESs [3Im:PTSA] and [4Im:PTSA] were prepared by imidazole (Im) and p-toluenesulfonic acid (PTSA), which were experimentally screened from a series of organic acids with imidazole. α, β-Unsaturated carbonyl compounds were obtained in good to excellent yields under solvent-free conditions with fast reaction rate. These two DESs can be reused for multiple times with no loss of catalytic activity.

An efficient Knoevenagel condensation of aldehydes with active methylene compounds over novel, robust CeZrO4−δ catalyst

In the present work, we explored novel CeZrO4−δ as a catalyst for Knoevenagel condensation of aldehydes with reactive methylene compounds like malononitrile and ethylcyanoacetate. For the present study, ceria, zirconia and CeZrO4−δ were prepared by gel combustion method and well characterized using XRD, SEM, EDX, BET and TPD analyses, etc. A wide range of aldehydes were effectively condensed over novel CeZrO4−δ with reactive methylene compounds with high yields. In addition, the CeZrO4−δ was effectively reused for five consecutive cycles without significant loss in its activity. To the best of our knowledge, this is the first liquid-phase application of pure CeZrO4−δ.

Synthesis and Cytotoxicity Evaluation of a Series of 3-Alkenyl-2-Hydroxy1,4-Naphthoquinones Obtained by an Efficient Knoevenagel Condensation

A modified and efficient Knoevenagel condensation procedure was developed to synthesize the title compounds using β-alanine and acetic acid as catalysts, showing good to excellent yields. We used lawsone with suitable aliphatic aldehydes including isobutyraldehyde, 3-methyl-butyraldehyde, 2-ethylbutyraldehyde, phenylacetaldehyde, 2-phenyl-propionaldehyde, among others. These compounds were submitted to cytotoxic screening against three tumor cell lines presenting good to excellent cytotoxic profiles.

Synthesis of Fe3O4@P4VP@ZIF-8 core-shell microspheres and their application in a Knoevenagel condensation reaction

In this work, a core-shell magnetic composite Fe3O4@P4VP@ZIF-8 microspheres were successfully designed and synthesized. A polymerization approach on the surface of pre-made Fe3O4 microspheres was employed for the synthesis of Fe3O4@P4VP. The zinc-derived Zeolite Imidazolate Framework (ZIF) shell was introduced through a layer-by-layer strategy. The obtained Fe3O4@P4VP@ZIF-8 core-shell structure was employed as an efficient Knoevenagel condensation catalyst for a variety of aldehydes. Furthermore, the inner P4VP layer also served as a basic additive in the condensation reaction process, while much less homogeneous basic additive was used. High catalytic reaction efficiency was achieved when the P4VP layer was utilized in combination with a Lewis acidity bearing ZIF-8 layer. The Fe3O4@P4VP@ZIF-8 catalyst was tested for recyclability and no drop in the catalytic activity was observed after more than five cycles.

Facile Preparation of α-Cyano-α,ω-Diaryloligovinylenes: A New Class of Color-Tunable Solid Emitters.

An efficient Knoevenagel condensation reaction was used to construct a series of α-cyano-α,ω-diaryloligovinylenes, which show prominent fluorescence emission in the solid state. On investigating the effect of conjugation length on fluorescent properties, we found that the diene structure showed superior solid-state luminescence. Furthermore, the emission color could be adjusted by introducing donor or acceptor functional groups at the terminal aryl groups. Full-color emission in the visible region can be achieved by adding different functional groups to the α-cyano-α,ω-diaryldivinylene moiety. The structure-property relationships were elucidated and some observations such as the substitution position effects were discussed. These compounds have potential applications as full-color solid emissive candidates in material science and their simple structures allow them to be easily modified resulting in further interesting properties.

First report of the application of simple molecular complexes as organo-catalysts for Knoevenagel condensation

A series of molecular complexes have been designed, synthesized and used as organo-catalysts for the first time for very efficient Knoevenagel condensation.

ChemInform Abstract: Nano‐Fe3O4 Encapsulated‐Silica Particles Bearing 3‐Aminopropyl Group as a Magnetically Separable Catalyst for Efficient Knoevenagel Condensation of Aromatic Aldehydes with Active Methylene Compounds.

AbstractThe preparation of a new 3‐aminopropyl‐functionalized Fe3O4/SiO2 catalyst is described which is used for the Knoevenagel condensation of aromatic aldehydes with active methylene compounds.

Lipase-catalyzed Knoevenagel condensation between α,β-unsaturated aldehydes and active methylene compounds

Abstract A simple and efficient Knoevenagel condensation between α,β-unsaturated aldehydes and active methylene compounds is reported. Notably, this condensation can be catalyzed by PPL (lipase from porcine pancreas) with satisfied yields (49%–92%). Moreover, PPL induces moderate Z/E selectivity in the Knoevenagel condensation.

Aqueous DABCO, an efficient medium for rapid organocatalyzed Knoevenagel condensation and the Gewald reaction

In the presence of water and 1,4-diazabicyclo[2.2.2]octane, several aldehydes and cyclic ketones underwent efficient Knoevenagel condensation with malononitrile and ethyl cyanoacetate to produce the respective \alpha.\beta-unsaturated systems within fairly short time periods. As a result, high yields of conjugated products were easily obtained. Products could be engaged in a Gewald reaction, either stepwise or in situ, to produce efficiently their respective 2-aminothiophenes within 4--7 h.

Visible Light Induced Knoevenagel Condensation Catalyzed by Starfruit Juice of &amp;lt;i&amp;gt;Averrhoa carambola&amp;lt;/i&amp;gt;

Aqueous starfruit juice catalyzed a simple and efficient Knoevenagel condensation of aromatic aldehydes with malononitrile has been developed under visible light. Products were obtained in yields up to 98% after short reaction times and they were isolated by simple filtration in pure crystallization states. The method is green and economically viable. A plausible mechanism for photochemical Knoevenagel condensation reaction catalyzed by starfruit juice was also predicted.

ChemInform Abstract: Highly Efficient Knoevenagel Condensation Reactions Catalyzed by a Proline‐Functionalized Polyacrylonitrile Fiber.

AbstractPFAF is a highly efficient catalyst for the condensation of aromatic aldehydes and ethyl cyanoacetate or malononitrile.