Search results for "KNOEVENAGEL CONDENSATION"
showing 10 items of 18 documents
ChemInform Abstract: Dialkylimidazolium Dimethyl Phosphates as Solvents and Catalysts for the Knoevenagel Condensation Reaction.
2014
Knoevenagel condensation between benzaldehyde and ethyl cyanoacetate in the presence of an equimolar amount of 1,3-dialkylimidazolium dimethyl phosphate ionic liquids is investigated.
Soluble oligo(phenylenevinylene)s with electron withdrawing substituents for the use in light emitting diodes
2000
Poly(p-phenylenevinylene) (PPV) and its derivatives are one of the most widely used classes of phosphors in light emitting diodes. Central problems are the imbalanced charge carrier injection and transport properties due to the high lying conduction band. A series of good soluble oligo(phenylenevinylene)s (OPV) with five benzene rings and a variety of electron withdrawing and accepting substituents have been prepared and may serve as model compounds for PPV with increased electron affinity. The central ring of the OPVs is substituted with two octyloxy groups to ensure good solubility and the lateral styrene units carry further chromophoric groups of different electronic character. The synth…
Humic substances as catalysts in condensation reactions
2001
Humic substances (HS) demonstrate appreciable impact on the rate of the condensation reactions as shown in the example of the reaction between hydrazine and 4-(dimethylamino)-benzaldhyde in an aquatic environment. The catalytic activity of HS has also been demonstrated in Knoevenagel and Claisen-Schmidt reactions for condensation of carbonyl compounds with CH acids. The aquatic fulvic acids are the most active in these reactions. The velocity of the studied reactions also depends on pH, temperature, the concentration and origin of HS used. A possible micellar and acid-base catalysis mechanism in aquatic media has been suggested.
Sequential Suzuki/Asymmetric Aldol and Suzuki/Knoevenagel Reactions Under Aqueous Conditions
2012
Here we describe for the first time a sequential Suzuki/asymmetric aldol reaction. Such sequential approach was achieved through the combined use of an ionic liquid supported palladium catalyst and the organocatalyst trans-4-(2,2-diphenylacetoxy)proline. Suzuki and asymmetric aldol reactions were performed under aqueous conditions. The use of a palladium catalyst under basic conditions allowed also the first example of sequential Suzuki/Knoevenagel reaction. Reactions were carried out under aqueous conditions and products were isolated in good to high yields and, in the case of the Suzuki/aldol reaction, with diastereoselectivities up to 91:9 and enantioselectivities up to at least 99 %.
Ionic liquids as solvents for the Knoevenagel condensation: understanding the role of solvent–solute interactions
2015
The Knoevenagel condensation in ionic liquids has been demonstrated as a strongly solvent-dependent process. The objective of this study was to establish a simple and descriptive trend of solvent–solute interactions that favour the Knoevenagel condensation in ionic liquid media. The reaction between 4-(dimethylamino)benzaldehyde and ethyl cyanoacetate in several imidazolium- and pyrrolidinium-based ionic liquids and one ionic liquid mixture was studied. The rate constants were rationalised by studying the change in the 1H NMR chemical shift of representative starting materials in the ionic liquids and the measurement and consideration of the Kamlet–Taft descriptors for each solvent. The hyd…
5-Oxo-1,4-dihydroindenopyridines: Calcium modulators with partial calcium agonistic activity
1990
The title compounds 4a-g were prepared by Knoevenagel reactions of 1,3-indandione (1) with the aromatic aldehydes 2a-g followed by cyclizing Michael addition of the products thus obtained with methyl β-aminocrotonate (3). The structures of products 4 were characterized by spectal data. Positive inotropic activities were observed on electrically stimulated, left atria of giunea pigs and these effects could be attributed to calcium agonism. On the other hand, barium chloride-induced contractions of guinea pig ileum were inhibited in a dose-dependent manner.
ChemInform Abstract: 5-Oxo-1,4-dihydroindenopyridines: Calcium Modulators with Partial Calcium Agonistic Activity.
1990
The title compounds 4a-g were prepared by Knoevenagel reactions of 1,3-indandione (1) with the aromatic aldehydes 2a-g followed by cyclizing Michael addition of the products thus obtained with methyl β-aminocrotonate (3). The structures of products 4 were characterized by spectal data. Positive inotropic activities were observed on electrically stimulated, left atria of giunea pigs and these effects could be attributed to calcium agonism. On the other hand, barium chloride-induced contractions of guinea pig ileum were inhibited in a dose-dependent manner.
Skābekļa atomu saturošie imidazolija sāļi kondensācijas reakcijās
2021
Skābekļa atomu saturošie imidazolija sāļi kondensācijas reakcijās. Gradovska L., darba vadītāji Dr.h.ķīm., prof. Zicmanis A., Dr.chem. Baķis E. Maģistra darbs, 59 lappuses, 31 attēls, 5 tabulas, 43 literatūras avoti, 1 pielikums. Latviešu valodā. Literatūras apskatā apkopota informācija par biežāk aprakstītajiem jonu šķidrumiem un polietilēnglikola funkcionalizētajem jonu šķidrumiem, to iegūšanu un izmantošanas iespējām organiskajā katalīzē. Eksperimentālajā daļā sintezēti polietilēnglikola, spirtu un alkilvirkņu funkcionalizētie imidazolija rindas jonu šķidrumi, kuri izmantoti kā katalizatori un reakcijas vide Knēvenāgela kondensācijā. Reakcijas konversija atkarībā no laika novērtēta, izma…
Dialkylimidazolium dimethyl phosphates as solvents and catalysts for the Knoevenagel condensation reaction
2014
Abstract The reaction between benzaldehyde and ethyl cyanoacetate is investigated in 1,3-dialkylimidazolium salts as solvents. The impact of both ions in these ionic liquids on the yield of the condensation reaction product is examined. Potentiometric titrations are employed for quantitative analyses of the best ionic liquids, revealing these to be 1,3-dialkylimidazolium dimethyl phosphates.
A DFT study of IRMOF-3 catalysed Knoevenagel condensation
2011
It has been recently reported that IRMOF-3 [Gascon et al., J. Catal, 2009, 261, 75] may behave as a basic catalyst, active in the Knoevenagel condensation. In particular, it has been shown that the basicity of aniline-like amino moieties is enhanced, along with the catalytic activity, when incorporated into MOF structures. The computational study here was aimed at finding possible atomistic explanations of the increased basicity and catalytic activity of the IRMOF-3 embedded aniline groups, experimentally claimed. It was, moreover, aimed at guessing a reaction mechanism for the IRMOF-3 catalysed Knoevenagel condensation of benzaldehyde and ethyl-cyanoacetate. Within the DFT framework we hav…