Knoevenagel Condensation Of Aromatic Aldehydes Research Articles

Solvent-Free Enzymatic Synthesis of Ethyl 3-Oxobutyrate Derivative: Characterization and Optimization of Reaction Condition.

It was first found that porcine pancreatic lipase (PPL) could catalyze the Knoevenagel condensation of aromatic aldehydes and ethyl acetoacetate under solvent-free conditions in this paper. Under solvent-free conditions, the highest yield of PPL catalytic reaction was 99.38%, and the Z/E selectivity of the product was 3.93. In addition, the reaction conditions were optimized, and the factors affecting the product structure were studied.

Bentonite clay as a novel base heterogeneous catalyst in Knoevenagel Condensation of aldehydes with ethyl cyanoacetate in water

Facilely available and cost-efficient bentonite clay was physically purified and chemically modified to investigate the catalytic activity in the heterogeneous catalysis in Knoevenagel condensation of aromatic aldehydes with ethyl cyanoacetate. The classical method of performing this reaction has various environmental issues and limits its industrial applications. This study, to develop modified bentonite clay as a heterogeneous base catalyst for use in Knoevenagel condensation as an alternative to hazardous base catalysts like pyridine, piperidine, etc., Here, the catalytic activities of purified and other incorporated bentonite clays were investigated for the Knoevenagel condensation of aromatic aldehydes with ethyl cyanoacetate. A comparison was made between the catalytic properties of unmodified purified bentonite clay and different metal-incorporated bentonite clays. These catalysts give excellent yields and are inexpensive and easily recyclable for this reaction.

Generation of Strong Basicity in Metal-Organic Frameworks: How Do Coordination Solvents Matter?

Solid strong bases with an ordered pore structure (OPS-SSBs) have attracted much attention because of their high catalytic activity and shape selectivity as heterogeneous catalysts in various reactions. Nevertheless, high temperatures are required to fabricate OPS-SSBs by using traditional methods. Herein, we report for the first time that the coordination solvents affect basicity generation in metal-organic frameworks (MOFs) greatly and that strong basicity can be formed at comparatively low temperatures. A typical MOF, MIL-53, was employed, and three different solvents, namely, water, methanol, and N,N-dimethylformamide (DMF), were coordinated, respectively, by means of solvent exchange. Thermogravimetry-mass spectrometer analysis shows that the conversion temperature of base precursor KNO3 is quite different on MIL-53 coordinated with different solvents. The conversion of KNO3 to basic sites takes place at 350, 300, and 250 °C on MIL-53 coordinated with water, methanol, and DMF, respectively. It is fascinating to observe the generation temperature of strongly basic sites at 250 °C, which is noticeably lower than that on various supports, such as mesoporous silica SBA-15 (600 °C), zeolite Y (700 °C), and metal oxide ZrO2 (730 °C). This is due to the redox interaction between coordination solvents and KNO3, leading to a significant decrease in the temperature for KNO3 conversion. Consequently, OPS-SSBs were prepared successfully with an ordered pore structure and strong basicity. The obtained OPS-SSBs show good shape selectivity in Knoevenagel condensation of aromatic aldehydes with different active methylene compounds. Moreover, these solid bases are highly active in the synthesis of dimethyl carbonate through transesterification reaction. This work might open up a new avenue for the fabrication of various functional materials at low temperatures through redox interactions.

One-pot three-component synthesis of a new series of tetrahydrobenzofuran-chromone conjugates

An efficient one-pot three-component protocol for the synthesis of novel tetrahydrobenzofuran-chromone conjugates using 3-formylchromones and 1,3-cyclohexandiones in the presence of a variety of alkyl or aryl isocyanides was developed. The reaction sequence consists of an initial Knoevenagel condensation of aromatic aldehydes with 1,3-cyclohexandione derivatives, followed by a [4 + 1] cycloaddition of with isocyanides, and then imine-enamine tautomerization to afford the products.

Facile synthesis and characterization of some new 5-arylidene-thiazolidine-2,4-diones and their antimicrobial evaluation

A series of novel 5-arylidene-thiazolidine-2,4-diones derivatives have been synthesized by the Knoevenagel condensation of aromatic aldehydes and N-substituted thiazolidinedione-2,4-diones. Use of KAl(SO 4 ) 2 •12(H 2 O) i . e . Alum for the reaction makes this synthesis facile because of several advantageous factors viz . non-toxicity, efficient catalytic ability and cheap cost of alum. Substitution of arylidene moiety at the position 5 on the thiazolidine-2,4-diones nucleus has occured using this facile approach. Synthesized derivatives have been characterized using various analytical tools and antimicrobial evaluation thereof has been performed against Gram-positive, Gram negative bacteria and a fungal strain. All synthesized compounds show moderate to very good activity against the microorganisms that they have been tested against.

Polyamine-functionalized carbon dots as active catalyst for Knoevenagel condensation reactions

In this study, carbon dots coated with diluted polyethylene imine was prepared from the carbonization of citric acid (CA) with branched polyethylene imine (BPEI) at temperature (200 °C), designated as BPEI-CDs. The solid catalyst was characterized by various techniques including X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR), atomic force microscopy (AFM), high resolution transmission electron microscopy (HRTEM). The obtained BPEI-CDs are spherical graphite nanocrystals (averaging 5–10 nm). It was found that it could be used as heterogeneous catalyst for Knoevenagel condensation of aromatic aldehydes with malononitrile at 60 °C in ethanol. The Knoevenagel aromatic products were obtained with a moderate to excellent conversion within 2 h. The BPEI-CDs as catalyst was easily isolated from the reaction mixtures by simple filtration and reused for three times without significant loss of catalytic activity. There was also no contribution from the leached active species and conversion was only being possible in the presence of the prepared modified carbon dots.

The Immobilized Copper on Nickel Ferrite: A Magnetically Superior Nanocatalyst for Chemoselective and Knoevenagel Synthesis of Bisdimedones and 1,8-Dioxo-octahydroxanthenes under Solvent-Free Conditions.

Nowadays, bisdimedones and 1,8-dioxo-octahydroxanthenes are considered as biologically active materials. Due to this, the synthesis of the mentioned materials is the subject of more interest. Although most of the reported methods have their own merits, however, they generally require the use of expensive reagents, hazardous organic solvents, a tedious workup procedure and reduced recyclability of the applied catalyst system. Overcoming of the above mentioned drawbacks, therefore, encouraged us to investigate the capability of nanostructured NiFe2O4@Cu towards the synthesis of bisdimedones and 1,8- dioxo-octahydroxanthenes under green reaction conditions. Nanoparticles of NiFe2O4@Cu were prepared via a two-step procedure including the preparation of NiFe2O4 by solid-state grinding of Ni(OAc)2·4H2O and Fe(NO3)3·9H2O in the presence of NaOH followed by the immobilization of Cu(0) on the surface of NiFe2O4 nucleus via hydrazine hydrate reduction of Cu(NO3)2·3H2O. After the synthesis of NiFe2O4@Cu, the catalytic activity of the Cu-nanocatalyst towards Knoevenagel reaction of aromatic aldehydes with dimedone under different reaction conditions was investigated. The examinations showed that using the molar equivalents of aromatic aldehydes (1 mmol) and dimedone (2 mmol) in the presence of 0.15 g NiFe2O4@Cu under solvent-free conditions chemoselectively afforded structurally different bisdimedone products at 60°C and 1,8-dioxo-octahydroxanthenes at 120°C. In this study, magnetically, nanoparticles of NiFe2O4@Cu were prepared and then characterized using different analyses. The catalytic activity of the prepared Cu-nanocatalyst was also studied towards solvent-free Knoevenagel condensation of aromatic aldehydes with dimedone. All the reactions were carried out within 15-240 min to afford bisdimedone and 1,8-dioxo-octahydroxanthene products in high yields.

Solvent-Free FeCl3-Assisted Electrophilic Fluorine-Catalyzed Knoevenagel Condensation to Yield α,β-Unsaturated Dicarbonyl Compounds and Coumarins

A highly environmentally friendly procedure was developed for the Knoevenagel condensation of aromatic aldehydes with diethyl malonate in the presence of FeCl3 and N-fluorobenzenesulfonimide as a source of electrophilic fluorine under solvent-free conditions. The scope of the reaction was explored using commercially available substrates. The reaction with substituted salicylaldehydes afforded the corresponding coumarin derivatives which attract interest due to their potential medicinal importance.

Facile Catalyst-Free Synthesis of New Functionalized 1H-Pyrazolo[1,2-b]phthalazines

Some new derivatives of 3-amino-1-aryl-N-butyl-5,10-dioxo-5,10-dihydro-1H-pyrazolo[1,2-b]- phthalazine-2-carboxamide are synthesized via in situ Knoevenagel condensation of aromatic aldehydes with N-butyl-2-cyanoacetamide, which leads to 3-aryl-N-butyl-2-cyanoacrylamides. This is followed by the reaction with phthalhydrazide upon refluxing in ethanol under catalyst-free conditions. The products are characterized on the basis of IR, 1H and 13C NMR spectral data.

Binary copper and iron oxides immobilized on silica-layered magnetite as a new reusable heterogeneous nanostructure catalyst for the Knoevenagel condensation in water

In this study, a novel heterogeneous and reusable nanostructure catalyst was synthesized through the immobilization of bimetallic Cu–Fe mixed oxides on silica-layered magnetite. The prepared nanomagnetic Fe3O4@SiO2@CuO–Fe2O3 was characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction, Brunauer–Emmett–Teller analysis, thermogravimetric analysis, differential thermal gravity, a vibration sample magnetometer, transmission electron microscopy and inductively coupled plasma optical emission spectroscopy. The catalytic activity of this mesoporous nanocomposite was studied in the Knoevenagel condensation of aromatic aldehydes and malononitrile in water to afford benzylidenemalononitriles in high to excellent yields. The nanocatalyst was able to be recycled five times without a significant loss in catalytic activity. This nanostructure catalyst allows for mild reaction conditions and acceptable reaction times, while delivering the desired products in high purity and yield without the use of dangerous organic solvents.

Expedient Catalytic Access to Knöevenagel Condensation Using Sr3Al2O6 Nanocomposite in Room Temperature

Sr3Al2O6 nanocomposite was prepared by sol gel method using aluminum isopropoxide, strontium nitrate, acetylacetone and polyethylene glycol as template, followed by calcination at 900 °C. This nanocomposite was characterized by various techniques including X-ray powder diffraction, infrared spectroscopy, elemental analysis, scanning transmission microscope and transmission electron microscope. It was found that Sr3Al2O6 nanocomposite successfully catalyzes the Knoevenagel condensation of aromatic aldehydes with malononitrile in room temperature in ethanol. Expedient access to the corresponding Knoevenagel adducts in moderate to high yields within 6 min is promising. The recovered catalyst was reused for three times without significant loss of activity.

Synthesis and characterization of sulfamic acid supported on Fe3O4 nanoparticles: A green, versatile and magnetically separable acidic catalyst for oxidation reactions and Knoevenagel condensation

Sulfamic acid immobilized on diethylenetriamine functionalized Fe3O4 nanoparticles (SA‐DETA‐Fe3O4) was successfully prepared and characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), vibrating sample magnetometer (VSM), thermo gravimetric analysis (TGA), X‐Ray diffraction (XRD) and scanning electron microscopy (SEM). The sulfamic acid was found as a magnetically separable and highly active catalyst for the oxidative coupling thiols, oxidation of sulfides. Furthermore, the SA‐DETA‐Fe3O4 showed the high catalytic activity in Knoevenagel condensation of aromatic aldehydes with active methylene compounds (malononitrile and ethyl cynoacetate). The nanosolid catalyst could be easily recovered by a simple magnetic separation and reused for many cycles without deterioration in catalytic activity.

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.

Nano‐structured Magnesium Oxide as Efficient Recyclable Catalyst for Knoevenagel and Claisen‐Schmidt Condensation Reactions

AbstractNano‐structured magnesium oxide was prepared by calcining its hydromagnesite phase, obtained by simple precipitation using magnesium acetate and ammonium carbonate under ambient condition. This MgO was used as active and reusable catalyst for the Knoevenagel condensation of aromatic aldehydes with malononitrile and ethylcyanoacetate under solvent‐free conditions at room temperature. It also exhibits strong activity in solvent‐free base catalyzed Claisen‐Schmidt condensation of various substituted benzaldehydes with acetophenone. The basic sites of different strengths like surface hydroxyl groups, and low coordination O2− sites may be responsible for the above catalytic activity. The experimental results showed that the nano‐MgO has high catalytic activity and can be recycled without significant loss of its activity.

ChemInform Abstract: Triethylamine: A Potential N‐Base Surrogate for Pyridine in Knoevenagel Condensation of Aromatic Aldehydes and Malonic Acid.

Cinnamic acids are intermediates with significant potential for synthesis of several industrially important chemicals. Classically, cinnamic acids are produced through Knoevenagel condensation of aromatic aldehydes and malonic acid in the presence of an organocatalyst and large amounts of carcinogenic pyridine. An alternative pyridine free reaction scheme for Knoevenagel condensation of malonic acid and aromatic aldehydes was investigated by replacing pyridine with an aliphatic tertiary amine surrogate in toluene as the reaction medium. Of the three aliphatic tertiary amines used, namely, triethyl amine (TEA), trioctyl amine (TOA) and tributyl amine (TBA), only TEA afforded cinnamic acids in comparable yields to those obtained with pyridine. Validation through a computational analysis is attempted to provide an explanation for the observed role of TEA as an aliphatic N-base instead of TBA and TOA. The use of TEA as a mild base in place of pyridine can be seen as playing the dual role of a base catalyst as well as a phase transfer agent evidenced by the in-process ATR-FITR spectroscopy. Use of the TEA–toluene system in place of pyridine can be seen as resulting in a process that affords ease of handling, separation and recycling of the solvent and the catalyst.

ChemInform Abstract: New Facile, Eco‐Friendly and Rapid Synthesis of Trisubstituted Alkenes Using Bismuth Nitrate as Lewis Acid.

AbstractThis rapid Knoevenagel condensation of aromatic aldehydes with malononitrile proceeds under mild conditions in water as green solvent.

Triethylamine: a potential N-base surrogate for pyridine in Knoevenagel condensation of aromatic aldehydes and malonic acid

Triethyl amine was successfully examined as a potent N-base surrogate for Knoevenagel condensation to produce cinnamic acids without compromising product yield.

Ultrasound-Promoted Knoevenagel Condensation Catalyzed by KF-Clinoptilolite

Potassium fluoride-clinoptilolite, which is prepared from commercially available and cheap starting materials, was used as an efficient and recyclable catalyst for Knoevenagel condensation of aromatic aldehydes with active methylene compounds under ultrasound irradiation. Short reaction times, high yields of products, ease of recovery and catalyst reusability make this new method economic and efficient. Keywords: Condensation, KF-clinoptilolite, Knoevenagel, ultrasounds, zeolites.

BF3/nano-γ-Al2O3 Promoted Knoevenagel Condensation at Room Temperature

The Knoevenagel condensation of aromatic aldehydes with barbituric acid, dimedone and malononitrile occurred in the presence of BF3/nano-γ-Al2O3 at room temperature in ethanol. This catalyst is characterized by powder X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS).

Multifunctional Cu(II) organic–inorganic hybrid as a catalyst for Knoevenagel condensation

In this study, organic–inorganic hybrid materials based on polyoxometalate and copper coordination polymer, [CuI(4,4′-bipy)]3[PMo 10 VI Mo 2 V O40{CuII(2,2′-bipy)}] designated as CuMo-CP(1), were prepared and characterized by various techniques including X-ray powder diffraction (XRD), infrared spectroscopy (FT-IR), and elemental analysis. It was found that the CuMo-CP(1) can be used as an efficient heterogeneous bifunctional acid-base catalyst for Knoevenagel condensation of aromatic aldehydes and cyclohexanone with malononitrile or ethyl cyanoacetate at 60 °C in ethanol. Obtaining the corresponding Knoevenagel adduct in moderate to excellent conversion yields within 4 h is promising. The catalyst can be easily recovered from the reaction mixture and reused for three times without significant loss of activity.