Knoevenagel Condensation Of Aldehydes Research Articles

Defect Engineering in a Nanoporous Thulium-Organic Framework in Catalyzing Knoevenagel Condensation and Chemical CO2 Fixation.

Defect engineering is an extremely effective strategy for modifying metal-organic frameworks (MOFs), which can break through the application limitations of traditional MOFs and enhance their functionality. Herein, we report a highly robust nanoporous thulium(III)-organic framework, {[Tm2(BDCP)(H2O)5](NO3)·3DMF·2H2O}n (NUC-105), with [Tm(COO)2(H2O)]n chains and [Tm2(COO)4(H2O)8] dinuclears as metal nodes and 2,6-bis(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)pyridine (BDCP) linkers. In NUC-105, each of the four chains of [Tm(COO)2]n and the two rows of [Tm2(COO)4(H2O)8] units is unified by the organic skeleton, resulting in a rectangular nanochannel with dimensions of 15.35 Å × 11.29 Å, which leads to a void volume of 50%. It is worth mentioning that the [Tm2(COO)4(H2O)8] cluster is very rare in terms of its higher level of associated water molecules, implying that the activated host framework can serve as a strong Lewis acid. NUC-105a exhibited great heterogeneous catalytic performance for CO2 cycloaddition with epoxides under the reaction conditions (0.60 mol % NUC-105a, 5.0 mol % n-Bu4NBr, 65 °C, 5 h), ensuring exclusive selectivity and high conversion rates. In addition, NUC-105a's strong catalytic impact on the Knoevenagel condensation of aldehydes and malononitrile can be attributed to the collaboration between the drastically unsaturated Lewis acidic Tm3+ centers and Lewis basic pyridine groups.

Enhanced catalytic performance for CO2 cycloaddition and Knoevenagel condensation reactions via stable Eu3+ modified Mn-MOF

The construction of MOF-based catalysts containing simultaneous Lewis acid and Lewis base sites has been considered as an efficient approach to enhance chemical fixation of CO2 into value-added products and Knoevenagel condensation reaction. Herein, one novel Eu3+-modified Mn-MOF (Eu3+@Mn-MOF-1) was successfully synthesized by solvothermal synthesis and post-synthesis modification. In Mn-MOF-1, the alternating chains with single and double carboxylate bridges are connected by H2L4− ligands to form a three-dimensional framework with 1D channels along a axis. Interestingly, the activated state of Eu3+@Mn-MOF-1 (noted as Eu3+@Mn-MOF-1a) with the removal of coordinated and lattice H2O molecules displayed excellent thermal stability. Furthermore, it is worth emphasizing that the inner surfaces of Eu3+@Mn-MOF-1a are functionalized by pentiful Lewis acid sites (tri- and penta-coordinated Mn2+ ions and modified Eu3+ ions) and Lewis base sites (uncoordinated Ocarboxylate and Npyridine). By virtue of the abundant co-existing Lewis acid-base sites, Eu3+@Mn-MOF-1a exhibited high catalytic performance for the cycloaddition of CO2 with epoxides and Knoevenagel condensation of aldehydes and malononitrile with preferable repeatability under mild conditions without the requirement of any solvent. Moreover, Eu3+@Mn-MOF-1a performed much higher activity for the cycloaddition of CO2 with epoxides than Mn-MOF-1a under the same conditions. In addition, Eu3+@Mn-MOF-1a also shows the yield of benzylidenemalononitrile can reach 99.9 % at room temperature within 1 h, representing about 1.3-fold increase compared to that of Mn-MOF-1a (76.0 %). The improvement of catalytic performance suggested the contribution of Eu3+ ions to the reaction. Hence, this work provides an efficient approach for the construction of MOFs with Lewis base sites by elaborately designing organic ligands and Lewis acid sites by post-synthetic modification to expose and/or introduce more unsaturated metal sites.

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.

A highly robust {ZnTb}n-Organic framework for excellent catalytic performance on cycloaddition reaction of epoxides with CO2

Effective chemical fixation of CO2 into high value-added industrial raw materials, recognized as an effective strategy to alleviate energy crisis and environmental pollution, makes the research of innovative catalysts a hot topic. Herein, a robust {ZnTb}n-chain-based framework of {[ZnTb(CPPDP)(H2O)]·5DMF·H2O}n (NUC-62) achieved from the solvothermal condition was reported. In NUC-62, nanoporous channels (aperture ca. 10.5 Å) are shaped by six rows of {ZnTb(CO2)5(H2O)}n chains, which is the first reported 3d-4f heterometallic chain with the staggered arrangement of Zn2+ and Tb3+. As for the activated NUC-62a with the removal of lattice and coordinated DMF and H2O, the host framework characterizes the merits of exposed Lewis-acidic metal sites, high specific surface, large void volume and stable chemical property. Furthermore, NUC-62a was tested as a heterogenous catalyst for the two organic reactions of cycloaddition of CO2 with epoxides and Knoevenagel condensation of aldehydes and malononitrile, in which NUC-62a display the high catalytic performance along with high selectivity and excellent recyclability. Hence, this work provides an effective synthesis strategy for MOFs-based catalysts.

θ-[Mo8O26]4--based multifunctional hybrid material for high catalytic performance on the cycloaddition of CO2, esterification and knoevenagel condensation.

Developing materials with excellent properties has become the norm in the field of basic research, prompting us to explore highly robust hybrid materials based on electron-rich POMs and electron-deficient MOFs. Herein, a θ-[Mo8O26]4--based hybrid material of [Cu2(BPPP)2]{θ-[Mo8O26]} (NUC-62) with excellent physicochemical stability was self-assembled under acidic solvothermal conditions from Na2MoO4 and CuCl2 in the presence of a designed chelated ligand of 1,3-bis(3-(2-pyridyl)pyrazol-1-yl)propane (BPPP), which has sufficient coordination sites, spatial self-regulation and great deformation ability. In NUC-62, each of two tetra-coordinated CuII ions and two BPPP are unified into one dinuclear unit serving as the cation, which is interactively linked to θ-[Mo8O26]4- anions via rich hydrogen bonds of C-H⋯O. Because of the unsaturated Lewis acidic CuII sites, NUC-62 exhibits high catalytic performance on the cycloaddition reactions of CO2 with epoxides under mild conditions with a high turnover number and turnover frequency. Furthermore, NUC-62, as a recyclable heterogeneous catalyst, shows high catalytic activity for the esterification of aromatic acid under refluxing, which is much better than the inorganic acid catalyst of H2SO4 in terms of turnover number and turnover frequency. Moreover, because of open metal sites and rich terminal oxygen atoms, NUC-62 shows high catalytic activity for Knoevenagel condensation reactions of aldehydes and malononitrile. Hence, this study lays the groundwork for constructing heterometallic cluster-based microporous MOFs with excellent Lewis acidic catalysis and chemical stability. Therefore, this study lays a foundation for the construction of functional polyoxometalate complexes.

Proline-Cu Complex Based 1,3,5-Triazine Coated on Fe3O4 Magnetic Nanoparticles: A Nanocatalyst for the Knoevenagel Condensation of Aldehyde with Malononitrile

Proline-Cu Complex Based 1,3,5-Triazine Coated on Fe₃O₄ Magnetic Nanoparticles: A Nanocatalyst for the Knoevenagel Condensation of Aldehyde with Malononitrile

Confined-based catalyst investigation through the comparative functionalization and defunctionalization of Zr-MOF.

In metal–organic frameworks, confined space as a chemical nanoreactor is as important as organocatalysis or coordinatively unsaturated metal site catalysis. In the present study, a set of mixed-ligand structures with UiO-66 architecture have been prepared. To the best of our knowledge, for the first time, structures derived by the solvothermal mixing ligand method and ultrasonic-assisted linker exchange approaches have been compared. Additionally, the relationship between the preparation method, structural properties, and catalytic efficiency of the prepared materials in the Knoevenagel condensation of aldehydes has been investigated. The prepared catalyst is very stable and can be recovered and reused for at least ten periods.

Synthesis and Characterization of Novel Pyridine Periodic Mesoporous Organosilicas and Its Catalytic Activity in the Knoevenagel Condensation Reaction.

The preparation of novel organic-inorganic hybrid mesoporous organosilica containing pyridinedicarboxamide functional groups uniformly distributed inside the nanostructured pore walls has been addressed. The mesoporosity and uniformity of the synthesized nanomaterials were characterized by different techniques such as nitrogen adsorption/desorption measurements and powder X-ray diffraction (PXRD). Additionally, the presence of the pyridinedicarboxamide in the pore walls of the nanomaterials was assessed by Fourier-transform infrared spectroscopy (FT-IR), as well as 29Si and 13C solid-state cross-polarization and magic angle spinning nuclear magnetic resonance (CP/MAS-NMR). The Knoevenagel condensation of aldehydes with active methylene compounds was carried out over the pyridinedicarboxamide functionalized mesoporous organosilica, which has been proven to be an efficient heterogeneous basic catalyst in the presence of ethanol as solvent. The catalytic activity of the investigated materials was investigated in the Knoevenagel condensation between malononitrile and several benzaldehyde derivatives exhibiting a high conversion (>90%) and excellent selectivity toward the final condensation products under very mild reaction conditions. Furthermore, the catalyst stability is noteworthy as it could be recycled and reused at least twelve times without any significant change in the performance.

Microwave‐associate synthesis of Co3O4 nanoparticles as an effcient nanocatalyst for the synthesis of arylidene barbituric and Meldrum's acid derivatives in green media

In this study, Co3O4 nanocatalysts were constructed in environmentally appropriate conditions using controlled, effective, and facile microwave method. The final nanostructures were characterized by SEM, XRD, and TEM analyses. The products had a small size distribution, homogeneous morphology, and crystallographic structures associated with the formation of Co3O4 nanostructures. Moreover, EDS mapping analysis confirmed the existence of Co and O elements in the final structure, and the magnetic properties of the samples were investigated by VSM. The application of this nanostructure in a catalytic process was further examined, and the results suggested that it could be used as a novel candidate for the synthesis of arylidene barbituric and Meldrum,s acid through Knoevenagel condensation of aldehydes by barbituric and Meldrum,s acid in aqueous media. The high yield of these nanocatalysts would be justified by the nature of the nanostructure as well as the experimental procedure developed in this study, which affected the physicochemical features of the products.

Efficient Knoevenagel Condensation catalyzed by Nickel Complexes

During recent years transition metal has found its way to the synthesis of biologically active natural product in organic synthesis. The continue internet to synthesis of biologically active compound we have plan for development of Nickel catalyzed novel methodology, Knoevenagel condensation of aldehyde with ethyl cyano acetate to provide Alpha cyano ethyl cinnamate. The corresponding adducts were obtained in good yields (78-92%) under simple and clean condition.

Synthesis of a novel tetracationic acidic organic salt based on DABCO and its applications as catalyst in the Knoevenagel condensation reactions in water

Synthesis of a novel tetracationic acidic organic salt based on DABCO containing two sulfonic acid groups in the skeleton and four hydrogensulfate groups as counterion is described. Its catalytic efficiency in the Knoevenagel condensation of aldehydes with active cyclic methylene compounds in water is investigated. While 2,2'-(phenylmethylene)bis(3-hydroxy-5,5-dimethylcyclohex-2-enone) derivatives were obtained in 40-98% isolated yields in the reaction of aldehydes with dimedone, the corresponding Knoevenagel adducts were provided in 85-95% yields using 1,3-dimethylbarbituric acid. In addition, a DABCO-based polycationic organic salt polymer was prepared and characterized for the first time.

Catalyst-free and Solvent-free Cyanosilylation and Knoevenagel Condensation of Aldehydes

A simple catalyst-free and solvent-free method for the cyanosilylation of a variety of aldehydes with trimethylsilyl cyanide as well as the Knoevenagel condensation reaction of various aldehydes wi...

Synthesis, characterization and evaluation of novel benzothiazole clubbed chromene derivatives for their anti-inflammatory potential

A series of chromene derivatives (5a–f) were prepared by multistep synthesis process using 2-[3-phenyl prop-2-ene nitrile] 1,3-benzothiazole and dimedone using piperidine as catalyst in ethanol. The reaction was found to proceed via Knoevenagel condensation of aldehydes with benzothiazole, followed by the elimination to afford the 2-(benzo[d]thiazol-2-yl)-3-(aryl)acrylonitrile, which then undergoes Michael addition with 5,5-dimethyl-1,3-cyclohexanedione, followed by intramolecular O-cyclization to give the products. The structures of all novel constructed derivatives were corroborated by elemental analysis and spectral data (FT-IR, 1H-NMR, 13C-NMR and Mass). Subsequently, the compounds were tested for their in-vivo anti-inflammatory activity. This study revealed that these synthesized derivatives tend to have significantly anti inflammatory activity and shall prove as structural templates in the design and development of new anti inflammatory drugs.

Knoevenagel Condensation of Aldehydes and Ketones with Alkyl Nitriles Catalyzed by Strongly Basic Anion Exchange Resins under Continuous‐Flow Conditions

AbstractThe use of strongly basic anion exchange resins as catalysts for Knoevenagel condensations under continuous‐flow conditions was investigated. It was found that Amberlite FPA60 was an efficient solid base catalyst for the flow synthesis of 1,2‐disubstituted alkenyl nitriles from arylmethyl nitriles and aldehydes. On the other hand, the Knoevenagel reaction involving acetonitrile required elevated reaction temperatures, which necessitated a change to a thermally robust ammonium hydroxide polymer catalyst. The potential applications of these strongly basic anion exchange resins for multi‐step continuous‐flow synthesis were also demonstrated.

Boron doped g-C3N4 as an effective metal-free solid base catalyst in Knoevenagel condensation

In this paper, boron, sulfur and phosphor doped g-C3N4 materials (defined as CNBF, CNSF and CNPF, respectively) were successfully prepared by thermal copolymerization of dicyandiamide and imidazole ionic liquids. The CNBF catalysts exhibited significantly enhanced activity in various Knoevenagel condensation of aldehyde with malononitrile, which were typical base-catalyzed reactions, comparing with CNSF and CNPF catalysts. The detailed characterizations of Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), High angle annular dark field-scanning transmission electron microscopy (HADDF-STEM) and 11B solid-state MAS NMR showed that boron was evenly doped in tri-s-triazine rings of g-C3N4 by substituting the carbon sites. In addition, CO2 Temperature programed desorption (CO2-TPD) characterizations indicated that the basic site concentration of CNBF catalysts was proportional to the doped boron content. Excluding the effect of specific surface area, the catalytic activity of CNBF catalysts followed the order CNBF-0.1 < CNBF-0.3 < CNBF-0.5 < CNBF-0.7, which was the same as that of boron content and basic site concentration. The catalytic performance revealed that boron-doping was an effective strategy to enhance the basicity of g-C3N4. This study will put forward the further application of boron-doped or boron-dominant two dimensional materials towards metal-free heterogeneous base catalysis.

Synthesis and characterization of push-pull bithiophene and thieno[3,2-b]thiophene derivatives bearing an ethyne linker as sensitizers for dye-sensitized solar cells

Five push-pull heterocyclic dyes 4–7, and 9 were synthesized and characterized in order to study the variations in the optical, electronic and photovoltaic properties induced by structural modifications, i.e. different spacer units and anchoring groups. The final push-pull conjugated dyes 6–7 and 9 are formed by a N,N-dimethylaniline donor moiety conjugated with bithiophene, ethynyl-bithiophene or ethynyl-thieno[3,2-b]thiophene spacers and cyanoacetic acid or rhodanine-3-acetic acid as anchoring group. The synthesis of the precursor aldehydes 4–5 was accomplished through a Sonogashira coupling, on the other hand, compound 8 was prepared by Suzuki coupling. Knoevenagel condensation of aldehydes 4, 5 and 8 with cyanoacetic acid or rhodamine-3-acetic acid afforded the final push-pull dyes 6, 7 and 9. Information on conformation, electronic structure and electron distribution was obtained by DFT and TDDFT calculations. This multidisciplinary study regarding the evaluation of the optical, redox and photovoltaic properties of the dyes reveals that compound 7, bearing an ethynyl-bithiophene spacer conjugated with a cyanoacetic acid anchoring group, has the highest conversion efficiency (3.51%) as dye sensitizer in nanocrystalline TiO2 solar cells. Co-adsorption studies were also performed for dyes 6–7 with N719 as co-adsorbent, and this enhanced dye efficiencies by 33–45%. The best cell performance was obtained by co-adsorbing N719 and dye 7 (75/25 vol%) with 4.66% efficiency.

Cytosine-functionalized SBA-15 mesoporous nanomaterials: Synthesis, characterization and catalytic applications

Periodic mesoporous silica functionalized by cytosine (Cyt@SBA-15) was prepared from Cytosine-chloropropyltriethoxysilane and tetraethoxysilane as precursors by a sol-gel method. The surface area and pore volume of Cyt@SBA-15 were 490 m2/g and 0.77 cm3/g. Due to their porous structure and active functional groups of cytosine on the pore of the hybrid material (Cyt@SBA-15), its catalytic performance was studied in the Knoevenagel condensation of aldehydes and ketones with malononitrile to α, β-unsaturated dicyanides in the presence of ethanol as solvent. The catalyst exhibited an excellent activity and selectivity toward the final condensation product under mild reaction conditions. Furthermore, the catalyst could be recovered and reused several times without any significant loss in either activity or product selectivity.

Knoevenagel Condensation of Aldehydes and Ketones with Malononitrile Catalyzed by Amine Compounds-Tethered Fe3O4@SiO2 Nanoparticles

A new magnetic nanoparticle supported-catalyst was developed for the Knoevenagel condensation between malononitrile and several aldehydes. The Fe3O4@SiO2-3N (where 3N = N1-(3-trimethoxysilylpropyl)diethylenetriamine) catalyst was characterized by XRD, infrared spectroscopy, and thermogravimetric analysis. The reactions provide excellent yields in a shorter reaction time in relation to others reported in the literature. The catalyst was easily recovered and reused until six times without significant loss of its catalytic capacity.

Solvent-Free Selective Condensations Based on the Formation of the Olefinic (C=C) Bond Catalyzed by Organocatalyst

Pyrrolidine and its derivatives were used to catalyze aldol and Knoevenagel condensations for the formation of the olefinic (C=C) bond under solvent-free conditions. The 3-pyrrolidinamine showed high activity and afforded excellent yields of α,β-unsaturated compounds. The aldol condensation of aromatic/heterocyclic aldehydes with ketones affords enones in high conversion (99.5%) and selectivity (92.7%). Good to excellent yields of α,β-unsaturated compounds were obtained in the Knoevenagel condensation of aldehydes with methylene-activated substrates.

ChemInform Abstract: The Convenient Synthesis of 11‐Methyl‐3,8‐disubstituted‐12‐aryl‐3,4,7,8,9,12‐hexahydro‐1H‐chromeno [2,3‐b]quinoline‐1,10(2H)‐dione Derivatives.

AbstractArylidene‐3‐oxobutanenitrile derivatives (III) prepared by Knoevenagel condensation of aldehydes with 3‐oxobutanenitrile, react with cyclohexanedione in ethylene glycol to give benzopyran derivatives (V).