2025-40-3Relevant academic research and scientific papers
Highly active hybrid mesoporous silica-supported base organocatalysts for C–C bond formation
Erigoni,Hernández-Soto,Rey,Segarra,Díaz
, p. 227 - 236 (2020)
New base hybrid catalysts, based on silyl-derivatives of molecules carrying amino, diamino, pyrrolidine, pyrazolium and imidazolium functionalities have been successfully achieved through post synthetic grafting onto M41S-type support. Different character
Mesoporous polymeric catalysts with both sulfonic acid and basic amine groups for the one-pot deacetalization-Knoevenagel reaction
Sun, Zunming,Yang, Xinyue,Huang, Xianpei,Zhang, Mengmeng,Bian, Guomin,Qi, Yonglin,Yang, Xinlin,Zhang, Wangqing
, p. 16676 - 16684 (2019)
A one-pot cascade reaction catalyzed by multifunctional catalysts is an economical and efficient pathway in modern organic synthesis. Herein, mesoporous polymeric materials with both sulfonic acid and basic amine groups have been synthesized by solvothermal-copolymerization of divinylbenzene (DVB) and 4-styrenesulfonic sodium (StSO3-Na+) with subsequent nitration, reduction of nitro to amino groups and acidification of sulfonic sodium to obtain P(DVB-NH2-StSO3H). The mesoporous polymeric bifunctional catalyst showed excellent activity and selectivity for one-pot cascade deacetalization-Knoevenagel condensation with facile recovery due to the isolated locations of the sulfonic acid and amino groups.
H3PW12O40/mpg-C3N4 as an efficient and reusable bifunctional catalyst in one-pot oxidation-Knoevenagel condensation tandem reaction
Wang, Hefang,Wang, Cunyue,Yang, Yongfang,Zhao, Meng,Wang, Yanji
, p. 405 - 417 (2017)
A single-site bifunctional catalyst for the oxidation-Knoevenagel condensation tandem reaction was prepared by the immobilization of phosphotungstic acid (HPW) on mesoporous graphitic carbon nitride (mpg-C3N4) via electrostatic interaction (HPW/mpg-C3N4). The results of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), solid-state 31P nuclear magnetic resonance (solid-state 31P NMR), zeta potentials, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) demonstrated that HPW was successfully immobilized on the protonated mpg-C3N4 by electrostatic interaction. The acid amounts of the catalysts were determined by NH3 temperature programmed desorption (NH3-TPD). The textural properties and morphology of HPW/mpg-C3N4 were characterized by N2 adsorption-desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). 30% HPW/mpg-C3N4 shows the best catalytic performance in the tandem reaction with 98.4% benzyl alcohol conversion and 96.2% selectivity to benzylidene malononitrile. The excellent catalytic performance of 30% HPW/mpg-C3N4 in the tandem reaction is due to the good catalytic performance of HPW in the oxidation and Knoevenagel condensation, respectively. Furthermore, protonated mpg-C3N4 not only acts as a support to facilitate good dispersion of HPW but also promotes the Knoevenagel condensation reaction effectively. Moreover, the HPW/mpg-C3N4 catalyst could be recycled easily without significant loss of catalytic activity.
Preparation of Nitrogen-Doped Carbon from Polyacrylonitrile and its Application as a Solid-Base Catalyst
Fujita, Shin-Ichiro,Katagiri, Ayaka,Watanabe, Hiroyuki,Asano, Sayaka,Yoshida, Hiroshi,Arai, Masahiko
, p. 2965 - 2970 (2015)
N-doped carbon (N carbon) materials were prepared from a commercial polyacrylonitrile (PAN) by calcination and subsequent ammoxidation and these were used for a model reaction of Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate. The catalyt
Acid-base catalysts derived from weakly acidic ion exchange resin: Efficiency in the Knoevenagel condensation
Saito,Goto,Honda,Fujii
, p. 7535 - 7538 (1992)
Weakly acidic cation-exchange resins in H+ form, partially neutralized with H2N(CH2)(n)N+Me3 OH- (n = 2-5), have been shown to catalyze the Knoevenagel condensation. The efficiency of catalysis depends on the aminoalkyl chain length and extent of neutralization.
Polystyrene Nanometer-Sized Particles Supported Alkaline Imidazolium Ionic Liquids as Reusable and Efficient Catalysts for the Knoevenagel Condensation in Aqueous Phase
Ma, Min,Li, Hansheng,Yang, Wang,Wu, Qin,Shi, Daxin,Zhao, Yun,Feng, Caihong,Jiao, Qingze
, p. 134 - 143 (2018)
Abstract: Polystyrene nanometer-sized particles supported alkaline 1-propyl imidazolium ionic liquids catalysts (nano-PS-CH2-[pIM][B]) were prepared and characterized by FT-IR, SEM, TG/DTA, BET and particle size distribution analysis. The resul
Stereodiversified Modular Synthesis of Non-planar Five-Membered Cyclic N-Hydroxylamidines: Reactivity Study and Application to the Synthesis of Cyclic Amidines
Prieto-Ramírez, Mary Cruz,Fernández, Israel,da Silva, Ivan,González-Platas, Javier,de Armas, Pedro,García-Tellado, Fernando
, p. 4362 - 4371 (2018)
A modular, stereodiversified and scalable synthesis of 5-membered cyclic N-hydroxylamidines endowed with three contiguous stereogenic centres is reported. The synthesis utilizes 2-cyano-3-aryl-4-nitro-alkynoates as key building blocks, which are provided by a novel 3-component Knoevenagel -Michael addition manifold carried out as an aqueous emulsion (on water). The key building blocks are obtained as separable mixtures of two series of diastereomers: 2,3,4-syn,syn and 2,3,4-syn,anti. Both series were separately transformed into the corresponding 5-membered 3,4,5-trisubstituted N-hydroxylamidines by a tandem hydrogenation cyclization reaction (stereodiversification phase). These N-hydroxylamidines are functionalized at C3-methinic position of the ring (alpha to the amidine function) by a robust and unprecedented N-amidinoxyl radical-mediated auto-oxidation process (hydroxylation), or by a diastereoselective enamine-based C?C bond forming manifold (creation of an all-carbon quaternary centre). The outcome of the latter is biased by the relative disposition of substituents in the ring, affording C3-quaternized 5-membered cyclic N-hydroxylamidines or 2,9-diazabicyclo[4.3.0]non-1-en motives. Finally, the Ti(III)-reduction of these quaternized N-hydroxylamidines generates the corresponding amidines in excellent yields. (Figure presented.).
Efficient bifunctional reactivity of K-doped CrO(OH) nanosheets: Exploiting the combined role of Cr(iii) and surface -OH groups in tandem catalysis
Vernekar, Dnyanesh,Ratha, Satyajit,Rode, Chandrashekhar,Jagadeesan, Dinesh
, p. 1154 - 1164 (2019)
This work reports the bifunctional catalytic activity of layered K-doped α-CrO(OH). The combined action of the redox active Cr(iii) and the surface hydroxyl groups was efficiently used to carry out 2-3 oxidation reactions in tandem followed by condensation/coupling reactions in one pot. Oxidation of benzyl alcohol followed by Knoevenagel condensation or coupling reactions forming C-C and C-N linkages in one pot is demonstrated. The catalyst has been characterized using XRD, IR, TGA, CO2-TPD, cyclic voltammetry, XPS and microscopic techniques to gain insight into the nature of active sites. The role of O- and O2- on the CrO(OH) catalyst in the bifunctional activity was studied using analytical techniques. Recyclability and leaching tests confirmed that K-α-CrO(OH) is a stable and environmentally safe catalyst.
Magnetic superbasic proton sponges are readily removed and permit direct product isolation
Schneider, Elia M.,Raso, Renzo A.,Hofer, Corinne J.,Zeltner, Martin,Stettler, Robert D.,Hess, Samuel C.,Grass, Robert N.,Stark, Wendelin J.
, p. 10908 - 10915 (2014)
Workup in organic synthesis can be very time-consuming, particularly when using reagents with both a solubility similar to that of the desired products and a tendency not to crystallize. In this respect, reactions involving organic bases would strongly be
Synthesis of cyclopropane-1,1,2,2-tetracarboxylic acid derivatives from aldehydes and CH-acids in the K2CO3/Bun 4NPF6/toluene heterogeneous system
Kryshtal, G. V.,Zhdankina, G. M.,Zlotin, S. G.
, p. 2286 - 2290,5 (2011)
A one-pot method for the synthesis of cyclopropane-1,1,2,2-tetracarboxylic derivatives was developed starting from aldehydes and cyanoacetic and 2-bromomalonic esters under heterogeneous conditions (K2CO 3/PhMe) in the presence of re
