Knoevenagel Condensation Products Research Articles

Pyridine immobilised on magnetic silica as an efficient solid base catalyst for Knoevenagel condensation of furfural with acetyl acetone

Novel heterogeneous pyridine immobilised magnetic silica (Fe3O4@SiO2-Py) was found to be an efficient, greener and heterogeneous solid base catalyst for the Knoevenagel condensation of furfural with acetylacetone under optimized reaction conditions. The Knoevenagel condensation product 3-(2-furylmethylene)-2,4-pentanedione (FMP), a jet fuel precursor, was produced in high yield of 85% with 94% conversion of furfural at 100 °C within a period of 4 h. Fe3O4@SiO2-Py catalyst showed excellent stability and recyclability without losing its initial activity.

Role of Aromatic Moiety in the Probe Property toward Picric Acid: Synthesis, Crystal Structure, Spectroscopy, Microscopy, and Computational Modeling of a Knoevenagel Condensation Product of d-Glucose.

Molecular probes for picric acid (PA) in both solution and solid states are important owing to their wide usage in industry. This paper deals with the design and development of a glucosyl conjugate of pyrene (L1) along with control molecular systems, possessing anthracenyl (L2), naphtyl (L3), and phenyl (L4) moieties, via Knoevenagel condensation of 2,4-pentanedione with d-glucose. The selectivity of L1 toward PA has been demonstrated on the basis of fluorescence and absorption spectroscopy, and the species of recognition by electrospray ionization mass spectrometry. The role of the aromatic group in the selective receptor property has been addressed among L1, L2, L3, and L4. The structural features of the {L1 + PA} complex were established by density functional theory computations. L1 was demonstrated to detect PA in solid state selectively over other nitroaromatic compounds (NACs). To study the utility of L1 in film, cellulose paper strips coated with L1 were used and demonstrated the selective detection of PA. The observed microstructural features of L1 and its complex {L1 + PA} differ distinctly in both atomic force microscopy and scanning electron microscopy, all in the support of the complex formation. Thus, L1 was demonstrated as a sensitive, selective, and inexpensive probe for PA over several NACs by visual, spectral, and microscopy methods.

A Synthesis of Novel Perinaphthenones from Acetylenic Esters and Acenaphthoquinone–Malononitrile Adduct in the Presence of Triphenylphosphine

A facile protocol involving Tebby zwitterions (PPh3-acetylenic esters) and the Knoevenagel condensation product of acenaphthylene-1,2-dione with malononitrile or ethyl cyanoacetate for the selective synthesis of a new series of perinaphthenone derivatives is described. Triphenylphosphine plays a catalytic role in these transformations. The structure of a typical product was confirmed by X-ray crystallography. The merits of this method include high yields of products, good atom economy, and a metal-free catalyst.

Synthesis and antimicrobial evaluation of some heterocyclic compounds from 3-aryl-1-phenyl-1H-pyrazole-4-carbaldehydes

Abstract A new series of chalcones, pyrazolinyl-pyrazoles, pyrazole-4-carbaldehyde oximes, pyrazole-4-carbonitriles, 5-pyrazolyl-1,2,4-triazolidine-3-thiones, and Knoevenagel condensation products was synthesized from 3-aryl-1-phenyl-1H-pyrazole-4-carbaldehydes. Most reactions were carried out either without solvent or in the presence of water as a green solvent. The structure of synthesized compounds was characterized by spectral and elemental analysis. The synthesized compounds were tested in vitro for their antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans in comparison with imipenem (intravenous β-lactam antibiotic) and clotrimazole (antifungal medication) as reference drugs by using the agar diffusion technique. 3-Aryl-1-phenyl-1H-pyrazole-4-carbonitriles 8b, 8c, and 8d showed significant antifungal activity against the fungus C. albicans.

DABCO-catalyzed Knoevenagel condensation of aldehydes with ethyl cyanoacetate using hydroxy ionic liquid as a promoter.

N-(2-Hydroxy-ethyl)-pyridinium chloride ([HyEtPy]Cl) was synthesized and explored as a novel promoter for 1,4-diazabicyclo [2.2.2] octane (DABCO)-catalyzed Knoevenagel condensation reactions, which showed better catalytic activity compared to other ionic liquid (IL) that had no hydroxyl group attached to the IL scaffold. The effect of hydrogen bond formation between the hydroxyl group of [HyEtPy]Cl and the carbonyl group of aldehyde played an important role in the Knoevenagel condensation reaction. In the [HyEtPy]Cl–H2O–DABCO composite system, Knoevenagel condensation reactions proceeded smoothly and cleanly, and the corresponding Knoevenagel condensation products were obtained in good to excellent yields in all cases examined. This protocol provides a versatile solvent–catalyst system, which has notable advantages such as being eco-friendly, ease of work-up and convenient reuse of the ionic liquid.

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.

Novel xanthene push-pull chromophores and luminophores: Synthesis and study of their spectral properties

Spectral properties of five derivatives of 4-aminochromene containing formylated partially hydrogenated five or six-membered cycles, and two derivatives of 4-aminochromen-2-ylidene-malonaldehyde have been studied. The cyclic derivatives absorb light with the maxima around 430, nm and emit near 550 nm with a luminescence quantum yield of 0.056–0.135 in acetonitrile solution. The non-cyclized derivatives of 4-aminochromene with a malonaldehyde moiety possess emission in solid state in the red region with a moderate Stokes shift of 43 nm and 67 nm. Derivatives of 4-aminochromene containing formylated partially hydrogenated five or six-membered cycles were derivatized with active CH-acids to give seven Knoevenagel condensation products. Absorption spectra of these condensation products in acetonitrile solutions are red-shifted by 102–184 nm, while emission maxima are red-shifted by only 71–117 nm, as compared to the corresponding initial formyl derivatives. In addition, the condensation products have 1.5–1.9 times higher extinction coefficient (60,600–79,600 M−1cm−1), while fluorescence quantum yields decreased to (0.003–0.034).

Small Molecules as Long-Wavelength Fluorophores: Push-Pull Substituted 4-Alkoxy-1,3-thiazoles

A series of donor-π-acceptor (D-π-A) substituted 4-hydroxythiazoles have been synthesized. Electron-donating groups (4-methoxyphenyl and 4-dimethylaminophenyl) were installed in the 5-position of the thiazole; thiophene/pyridine-bridged acceptors (formyl groups and their Knoevenagel condensation products) were placed in the 2-position. The influence of D-π-A character on the photophysical properties and electronic structure was investigated by means of UV/Vis and fluorescence spectroscopy.

Efficient one-pot synthesis of some new pyrimido[5′,4′:5,6]pyrido[2,3-d]pyrimidines catalyzed by magnetically recyclable Fe3O4 nanoparticles

The study is devoted to one-pot reaction of 1,3-dimethylbarbituric acid with aromatic aldehydes and ammonium acetate using Fe3O4 nanoparticles as efficient and magnetically recyclable catalysts. Aromatic aldehydes substituted with electron-withdrawing groups or none, reacted successfully with 1,3-dimethylbarbituric acid and ammonium acetate to give new pyrimido[5′,4′:5,6]pyrido[2,3-d]pyrimidine derivatives (can be also named as pyrido[2,3-d:6,5-d′]dipyrimidines) in high yields over relatively short reaction time. The Knoevenagel condensation products were isolated using aromatic aldehydes bearing electron-donating substituents. The catalyst could be efficiently used for four times without substantial reduction in its activity. The new products were characterized on the basis of FT-IR, 1H NMR and 13C NMR spectral data.

Recyclable Thermosets Based on Dynamic Amidation and Aza-Michael Addition Chemistry

Utilizing the dynamic amidation and aza-Michael addition chemistry, a set of high strength, recyclable, and self-healable covalent adaptable networks (CANs) are synthesized by reacting the precursor and commercial oligoamine cross-linkers under mild temperature (25–50 °C) and solvent-free conditions. The amide linkages present in these CANs are readily hydrolyzable under mild acidic (pH = 5.3) conditions, whereas the aza-Michael adducts with secondary amines are thermally reversible. Utilizing the above, these CANs are depolymerized under ambient conditions in mild acidic solution and recycled with retention of original mechanical properties. The crack on the material surface is self-healed at 50 °C. The precursor, a Knoevenagel condensation product of terephthalaldehyde and diethyl malonate, is easily synthesized in a large scale. Suitable model compounds are synthesized and studied to further understand the transformations involved in the polymerization–depolymerization of these networks. These networks...

Reaction of ninhydrin with enamino amides of the 3,3-dimethyl-1,2,3,4-tetrahydroisoquinoline series and drotaverine

“Push–pull” enamines of the 1,2,3,4-tetrahydroisoquinoline series, 2-(3,3-dimethyl-1,2,3,4-tetrahydroisoquinolin- 1-ylidene)acetamides, reacted as 1,3-binucleophiles with ninhydrin to form tricyclic tetrahydroindeno[1,2-b]pyrrole system. The nucleophilic centers in the enamines were the amide NH2 group and s-carbon atom of the enamine fragment. The reaction of ninhydrin with 2-[2,2-dimethyl-2,3-dihydrobenzo[f]-isoquinolin-1(4H)-ylidene]-1-(pyrrolidin-1-yl)ethanone involved only addition to the s-carbon atom of the enamine fragment. The different reaction directions were rationalized by steric effect of two methyl groups in position 3 of the isoquinoline ring. The Knoevenagel condensation product was obtained by the reaction of ninhydrin with drotaverine (base). The structure of the 1,3-addition product, (3aS,8bS,Z)-{2,2-dimethyl-2,3- dihydrobenzo[f]isoquinolin-4(1H)-ylidene}-3a,8b-dihydroxy-1,3,3a,8b-tetrahydroindeno[1,2-b]pyrrole-2,4-dione, was confirmed by X-ray analysis.

The Knoevenagel reaction of cyanoacetylhydrazine with pregnenolone: Synthesis of thiophene, thieno[2,3-d]pyrimidine, 1,2,4-triazole, pyran and pyridine derivatives with anti-inflammatory and anti-ulcer activities

The reaction of pregnenolone with cyanoacetylhydrazine and ammonium acetate at 120°C gave the Knoevenagel condensation product 3. The latter reacted with different reagents to give thiophene, thieno[2,3-d]pyrimidine, 1,2,4-triazole and pyran derivatives. The anti-inflammatory and anti-ulcer evaluations of the newly synthesized products were evaluated and the results showed that compounds 4, 8c, 10, 11, 13c, 15a, 15c, 17a, 17b, 17e, 18a and 18f possessed higher activity compared to the rest of the compounds. In addition to this, the toxicity of these active compounds was studied against shrimp larvae where compounds 15a, 15c and 18a showed non-toxicity against the tested organisms.

Iodine-Mediated Diastereoselective Cyclopropanation of Arylidene Malononotriles by 2,6-Dimethylquinoline

A novel iodine-mediated reaction of 2,6-dimethylquinoline with Knoevenagel condensation products of malononitrile with benzaldehydes, leading to a facile, one-pot synthesis of 2-aryl-3-(6-methylquinolin-2-yl)cyclopropane-1,1-dicarbonitriles, in moderate to good yields, is described.

Microwave-Assisted Synthesis of Fused 3-Thiocarbamoylquinolines by Reinhoudt Reaction and their Modification by Hantzsch Reaction

We have shown that the reaction of 2-dialkylaminobenzaldehydes with cyanothioacetamide leading to Knoevenagel condensation products and their cyclization according to tert-amino effect mechanism, may be significantly accelerated by using a microwave reactor. The synthesized tetrahydroquinolinо-3-carbothioamides reacted with α-bromoacetophenone in microwave reactor to give 3–(1,3-thiazol-2-yl)tetrahydroquinolines.

ChemInform Abstract: One‐Pot Four‐Component Approach for the Construction of Dihydropyridines and Dihydropyridinones Using Amines and Activated Alkynes.

AbstractThis is the first report on the synthesis of dihydropyridines using dimethyl acetylenedicarboxylate, primary amines, and in situ generated Knoevenagel condensation products.

Tandem synthesis of trichloromethylated [3.3.3]propellanes from trichloroacetamidines and a ninhydrin–malononitrile adduct

The trichloroacetamidine intermediates, generated by addition of benzylamine derivatives to trichloroacetonitrile, react with the Knoevenagel condensation product of ninhydrin and malononitrile to afford trichloromethylated [3.3.3]propellanes, in good yields. When benzylamine was used, a plane-symmetrical spiro-compound was obtained.

The Knoevenagel reactions of pregnenolone with cyanomethylene reagents: Synthesis of thiophene, thieno[2,3-b]pyridine, thieno[3,2-d]isoxazole derivatives of pregnenolone and their in vitro cytotoxicity towards tumor and normal cell lines

The reaction of pregnenolone with either 2-aminoprop-1-ene-1,1,3-tricarbonitrile or 3-oxo-3-phenylpropanenitrile gave the Knoevenagel condensation products 3 and 6, respectively. Separation of the E and Z isomeric compounds of 3 and 6 together with their structure elucidation were carried out. Some chemical transformations of the latter products were carried out and the cytotoxicity of the newly obtained products was evaluated against some cancer cell lines and a human normal cell line. The results indicated that compounds 15, 17a, 18 and 20e among the tested compounds showed the highest cytotoxicity against the cancer cell lines.

“On-water” organic synthesis: l-proline catalyzed synthesis of pyrimidine-2,4-dione-, benzo[g]- and dihydropyrano[2,3-g]chromene derivatives in aqueous media

In this work, functionalized pyrimidine-2,4-dione-, benzo[g]-, and dihydropyrano[2,3-g]chromene derivatives have been synthesized via a Michael addition of 2-hydroxy-1,4-naphthoquinone or 2,5-dihydroxy-1,4-benzoquinone to the Knoevenagel condensation product of an aldehyde with Meldrum’s acid, dimedone or barbituric acid in the presence of a catalytic amount of l-proline under refluxing conditions in water in good to excellent yields.

Synthesis of fused uracils: pyrano[2,3-d]pyrimidines and 1,4-bis(pyrano[2,3-d]pyrimidinyl)benzenes by domino Knoevenagel/Diels-Alder reactions.

Knoevenagel condensation of barbituric acids with aromatic aldehydes containing one or two formyl groups was carried out. 5-Arylidenebarbituric acids underwent smooth hetero-Diels-Alder (HDA) reactions with enol ethers to afford cis and trans diastereoisomers of pyrano[2,3-d]pyrimidine-2,4-diones and 5,5′-(1,4-phenylene)bis[2H-pyrano[2,3-d]pyrimidine-2,4(3H)-dione] derivatives in excellent yields (75–88 %). Syntheses were realized by Knoevenagel condensation and HDA reaction in four different reaction conditions: Knoevenagel condensation in water and Diels-Alder reaction in methylene chloride solution, Knoevenagel condensation in water and Diels-Alder reaction without solvent, three-component one-pot reaction in methylene chloride solution, or three-component one-pot reaction in water. All reactions were carried out without catalyst at room temperature. The reactions of malononitrile with Knoevenagel condensation products of barbituric acids and heteroaromatic aldehydes or terephthalaldehyde were examined and did not provide corresponding pyranopyrimidines.Graphical .

ChemInform Abstract: Solvent‐Free, Microwave Assisted Knoevenagel Condensation of Novel 2,5‐Disubstituted Indole Analogues and Their Biological Evaluation.

AbstractSynthesis of Knoevenagel condensation products (III), (V), (VII) and screening for their cytotoxic and antioxidant activities are described.