Knoevenagel Condensation Of Ethyl Cyanoacetate Research Articles

A Continuous-Flow Microreactor for Knoevenagel Condensation of Ethyl Cyanoacetate with Benzaldehyde: The Effect of Grafted Amino Groups on Catalytic Activity.

Ethyl α-cyanocinnamate was synthesized in the Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate in flow monolithic microreactor of 0.63 cm3 volume. The catalytically active core was made of silica monolith modified with various amine group precursors. Structural properties of the support, surface density of NHx groups, and catalytic activity were investigated. It was found that the poly- or di-amine groups attached to the silica surface appeared to be more effective than the aminopropyl groups. Microreactors grafted with diamine functional groups, accompanied by hydrophobic methyl groups, showed the highest activity and stability. It was proved that the decisive role on the activity of catalysts was exerted by the presence of primary amines in diamine chain. The reaction conditions were optimized and it was found that almost full substrate conversion could be achieved in 6 min at 50 °C in the microreactor with low concentration of diamine groups equal to 0.33 mmol g-1 .

Synthesis of highly substituted tetrahydroquinolines using ethyl cyanoacetate via aza-Michael-Michael addition.

A three-component cascade reaction involving 2-alkenyl aniline, aldehydes, and ethyl cyanoacetate in the presence of DBU to synthesize highly substituted 1,2,3,4-tetrahydroquinolines is reported. The reaction proceeded through the Knoevenagel condensation of ethyl cyanoacetate with aldehydes followed by the aza-Michael–Michael addition with 2-alkenyl anilines to prepare the tetrahydroquinoline scaffolds.

The role of gold dopant in AP-Nb/MCF and AP-MCF on the Knoevenagel condensation of ethyl cyanoacetate with benzaldehyde and 2,4-dichlorobenzaldehyde

The Knoevenagel condensation with chlorine substituted benzaldehyde is difficult because of deactivation of aldehyde group. In this work we have shown that the activity of mesoporous cellular foams (MCF and Nb/MCF), modified with 3-aminopropyl-trimethoxysilane (AP) as a source of basicity, can be enhanced for this reaction by the anchoring of gold species. Gold species were loaded on amine modified materials towards Au/AP-MCF and Au/AP-Nb/MCF. Moreover, copper was used as a dopant for the latter sample giving rise to AuCu/AP/MCF. All these materials were characterized in details by different complementary techniques (N2 adsorption isotherms, TEM, UV–vis, TG/DTA, XPS, DFT calculations) which allowed the evaluation of states of all components of the catalysts. The interaction between niobium species and AP was evidenced to increase the stability of the basic modifier. This interaction was weakened by the introduction of gold and copper. The presence of both, negatively charged gold nanoparticles (NPs) and gold cations was crucial for the activation of 2,4-dichlorobenzaldehyde via the interaction with chlorine substituent atoms and aldehyde oxygen atoms as well as breaking of the “pseudo hydrogen bond” between aldehyde hydrogen atom and chlorine substituent, which destabilized the structure making it more active. Gold dopants did not influence significantly the condensation of ethyl cyanoacetate with benzaldehyde.

Microwave Assisted Urea-Acetic Acid Catalyzed Knoevenagel Condensation of Ethyl Cyanoacetate and 1,3-Thiazolidine-2,4-dione with Aromatic Aldehydes under Solvent Free Condition

Microwave Assisted Urea-Acetic Acid Catalyzed Knoevenagel Condensation of Ethyl Cyanoacetate and 1,3-Thiazolidine-2,4-dione with Aromatic Aldehydes under Solvent Free Condition

Synthesis of α‐Dawson‐Type Silicotungstate [α‐Si2W18O62]8− and Protonation and Deprotonation Inside the Aperture through Intramolecular Hydrogen Bonds

The design of structurally well-defined anionic molecular metal-oxygen clusters, polyoxometalates (POMs), leads to inorganic receptors with unique and tunable properties. Herein, an α-Dawson-type silicotungstate, TBA8[α-Si2W18O62]⋅3 H2O (II) that possesses a -8 charge was successfully synthesized by dimerization of a trivacant lacunary α-Keggin-type silicotungstate TBA4H6[α-SiW9O34]⋅2 H2O (I) in an organic solvent. POM II could be reversibly protonated (in the presence of acid) and deprotonated (in the presence of base) inside the aperture by means of intramolecular hydrogen bonds with retention of the POM structure. In contrast, the aperture of phosphorus-centered POM TBA6[α-P2W18O62]⋅H2O (III) was not protonated inside the aperture. The density functional theory (DFT) calculations revealed that the basicities and charges of internal μ3-oxygen atoms were increased by changing the central heteroatoms from P(5+) to Si(4+), thereby supporting the protonation of II. Additionally, II showed much higher catalytic performance for the Knoevenagel condensation of ethyl cyanoacetate with benzaldehyde than I and III.

Amino-based metal-organic frameworks as stable, highly active basic catalysts

Metal-organic frameworks (MOFs) with non-coordinated amino groups, i.e. IRMOF-3 and amino-functionalized MIL-53, are stable solid basic catalysts in the Knoevenagel condensation of ethyl cyanoacetate and ethyl acetoacetate with benzaldehyde. IRMOF-3 DEF exhibits activities that are at least as high as the most active solid basic catalysts reported, with a 100% selectivity to the condensation product. For IRMOF-3 samples the catalytic activity correlated with the accessibility of the basic sites. Diffusion limitations could be excluded for this most active catalyst. A new MOF based on the MIL-53 topology and non-coordinated amino groups has been synthesized and characterized. Although active its poor performance in the studied Knoevenagel condensations is attributed to strong adsorption and diffusion limitations in the 1-D pore structure of this framework. The performance of the IRMOF-3 catalysts demonstrates that the basicity of the aniline-like amino group is enhanced when incorporated inside the MOF structure, increasing the p K a of the basic catalyst and more active than aniline as homogeneous catalyst. The IRMOF-3 catalysts are stable under the studied reaction conditions, and could be reused without significant loss in activity. The catalytic performance of IRMOF-3 in various solvents suggests that this open, accessible and well-defined structure behaves more like homogeneous basic catalysts, in contrast to other solid basic catalysts. By means of DRIFTS, the reaction mechanism has been elucidated, showing spectroscopic evidence of benzaldimine intermediates.

Solvent-Free L-Proline Catalysed Condensation of Ethyl Cyanoacetate with Aldehydes

Solvent-free Knoevenagel condensation of ethyl cyanoacetate with aromatic aldehydes, catalysed by environmentally friendly silica gel supported L-proline under microwave irradiation is studied.

Structure and Basicity of Mesoporous Materials from Mg/Al/In Layered Double Hydroxides Prepared by Separate Nucleation and Aging Steps Method

This paper presents the synthesis of mesoporous materials from hydrotalcite-like layered double hydroxides (LDHs) with the Mg2 +/(Al3 + + In3 +) molar ratio of 3.0 on the brucite-like lattice and the interlayer carbonate anions, using a novel separate nucleation and aging steps method developed in our laboratory. The physicochemical properties of as-synthesized LDHs and resulting calcined products at 500∘C were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), simultaneous thermogravimetric and differential thermal analysis (TG-DTA), 27Al nuclear magnetic resonance (NMR) and low-temperature nitrogen adsorption-desorption experiments. The results indicate calcination of LDHs with a well-crystallized single phase and nanoscale crystallites leads to the formation of the type MgO-like phase, and the pore size distributions of uncalcined and calcined LDHs are mostly in the range of mesopores. Furthermore, calcined materials have higher surface areas, pore volumes, pore diameters and surface basicities than corresponding precursors. When used as solid base catalysts for the Knoevenagel condensation of ethyl cyanoacetate with benzaldehyde, the material with higher density of base sites on the surface also exhibited a higher catalytic activity. Particularly, calcined MgAlIn-LDH has highest density of base sites resulting in a highest catalytic activity, as points to an important role of indium as a modifier of the surface properties of solid base catalysts.

Solvent‐Free Synthesis of Ethyl α‐Cyanocinnamates Catalyzed by K2O–Al2O3 Using Grinding Method

K2O–Al2O3 catalyzes the Knoevenagel condensation of ethyl cyanoacetate with aromatic aldehydes, giving ethyl α‐cyanocinnamates in 94–98% yield under solvent‐free condition by grinding at room temperature.

Microwave‐Assisted Knoevenagel Condensation of Ethyl Cyanoacetate with Aldehydes in Solvent‐Free Condition.

Piperazine has been used successfully as a catalyst for the Knoevenagel condensation of ethyl cyanoacetate and aromatic aldehydes along with the rate enhancement by microwave irradiation under solvent-free condition.

Solvent‐Free Synthesis of Ethyl α‐Cyanocinnamates Catalyzed by K2O—Al2O3 Using Grinding Method.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Microwave-assisted Knoevenagel condensation of ethyl cyanoacetate with aldehydes in solvent-free condition

Piperazine has been used successfully as a catalyst for the Knoevenagel condensation of ethyl cyanoacetate and aromatic aldehydes along with the rate enhancement by microwave irradiation under solvent-free condition.

Synthesis of ethyl α-cyanocinnamates catalyzed by KF–Al 2O 3 under ultrasound irradiation

Knoevenagel condensation of ethyl cyanoacetate with aromatic aldehyde catalyzed by KF–Al 2O 3 in ethanol results ethyl α-cyanocinnamates in 97–99% yield under ultrasound irradiation.

Synthesis of ethyl α-cyanocinnamates under ultrasound irradiation

Knoevenagel condensation of ethyl cyanoacetate with aromatic aldehydes catalyzed by pyridine results ethyl α-cyanocinnamates in 80–96% yields under ultrasound irradiation.

Synthesis and characterization of mixed Ga/Al-containing layered double hydroxides: study of their basic properties through the Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate, and comparison to other LDHs

Two series of mixed Ga/Al-containing LDHs, [MgR–Ga/Alα–CO3] and [MgR–Ga/Alα–NO3] (where R=M(II)/M(III)=3 and α=Ga/(Al+Ga)=0, 0.25, 0.50, 0.75, 1.0 in the starting solutions) were prepared following the coprecipitation method at constant pH. Their structural, thermal and textural properties were examined. When compared with the composition of the starting solutions, the solids show an incomplete incorporation of gallium probably due to the solubility of Ga(OH)3 species at the coprecipitation pH (9–10) used. The linear variation of the lattice parameters a and c vs. x=(Al+Ga)/(Mg+Al+Ga) clearly indicates that Al3+ and Mg2+ cations are isomorphically substituted by Ga3+ cations in the hydrotalcite structure. No influence of the relative concentrations of the cations on the thermal behavior was observed here as x only varies from 0.19 to 0.28. Nevertheless, a few differences are noted depending on the interlamellar anion. On the other hand, the basic reactivity of these new materials and their calcined derivatives was evaluated through the Knoevenagel condensation of ethyl cyanoacetate with benzaldehyde. Other LDHs containing divalent and trivalent cations of different electronegativity (M(II)=Mg2+, Cu2+, Zn2+; and M(III)=Al3+, Sc3+, Mn3+, Ga3+) as well as diverse simple anions (CO32−, NO3−, F−), were also tested in order to examine the relationship between the composition and the basic properties of LDHs. In addition, the number of base sites were quantified from the adsorption isotherms for phenol. Both calcined and uncalcined Mg,Ga/Al-hydrotalcites exhibit high reactivity. For the calcined LDHs, it appears that the basicity order found from the catalytic activity is related to the base site density and the average electronegativity of the solid, i.e., the basic strength.

Solvent-Free Microwave Enhanced Knoevenagel Condensation of Ethyl Cyanoacetate with Aldehydes

A high yielding and fast method of Knoevenagel condensation of ethyl cyanoacetate with various aldehydes under microwave irradiation using environment-friendly ammonium acetate in the absence of any solvent is described.

Microwave Enhanced Knoevenagel Condensation of Ethyl Cyanoacetate with Aldehydes

The reaction rate of Knoevenagel condensation can be dramatically enhanced by irradiating the reaction mixture containing ethyl cyanoacetate, an aldehyde, P2O5, piperidine, and chlorobenzene with a commercial microwave oven. A number of Knoevenagel condensation products were prepared in good yields in very short reaction times (2-15min) under the microwave irradiation.