Search results for "Catalysis"
showing 10 items of 5944 documents
Synthesis of pillar[7]arene
2012
Abstract The first synthesis of pillar[7]arene is reported with two methods. Method A: the FeCl 3 -catalyzed condensation reaction of 1,4-dimethoxybenzene ( 1 ) with paraformaldehyde in CHCl 3 gave dimethoxypillar[7]arene ( 3 ). Method B: the p -toluenesulfonic acid catalyzed condensation reaction of 2,5-bis(benzyloxymethyl)-1,4-dimethoxybenzene ( 2 ) in CH 2 Cl 2 gave compound 3 . Demethylation of 3 with BBr 3 gave pillar[7]arene ( 4 ). The pillar[7]arene might be a perspective macrocyclic host in host–guest chemistry.
Scandium-catalyzed preparation of cytotoxic 3-functionalized quinolin-2-ones: Regioselective ring enlargement of isatins or imino isatins
2012
Trimethylsilyldiazomethane in the presence of catalytic amounts of Sc(OTf) 3 smoothly promotes the ring expansion of isatins or imino isatins to efficiently afford 3-functionalized quinolin-2-ones through controlled ring enlargement. Whereas the ring-expansion reaction of azetidine-2,3-diones led to the adduct resulting from migration of the carbonyl group, the ring-expansion reaction of oxindole derivatives gave the adduct resulting from migration of the aryl group. To rationalize the experimental observations, theoretical studies have been performed. Moreover, the biological activity of some of the synthesized heterocycles has been evaluated in four cancer cell lines. © 2012 Wiley-VCH Ver…
A DFT study for the formation of imidazo[1,2-c]pyrimidines through an intramolecular Michael addition
2006
The formation of imidazo[1,2-c]pyrimidines through a ring closure of 2-(2-sulfonylimino-1,2-dihydro-1-pyrimidinyl) acetamides has been studied using DFT methods. Analysis of the energy results for the cyclization step shows the demand of almost an acid catalyst, which increases the electrophilicity of the dihydropyrimidine moiety, in order to make feasible the intramolecular Michael addition. The substitution on both dihydropyrimidine and amide moieties has also an influence on the cyclization step.
ChemInform Abstract: Ru(bpy)2Cl2: A Catalyst Able to Shift the Course of the Photorearrangement in the Boulton-Katritzky Reaction.
2016
Abstract The Boulton–Katritzky reaction represents one of the most popular and efficient strategies used to realize azole-into-azole conversions. For example, under different experimental conditions, it allows the rearrangement of Z-arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazoles (1) into 2-aryl-4-benzoylamino-5-phenyl-2H-1,2,3-triazoles (2) in very high yields. Moreover, we have recently realized this conversion also by UV-photostimulation. Now we have enlarged the scope of the reaction irradiating with visible or UV light an acetonitrile solution of some Z-arylhydrazones (1a–e) in the presence of catalytic amounts of Ru(bpy)2Cl2. We have observed the unexpected formation of the 1-a…
Synthese von Cyclo-urethanen
1962
Die Bis-chlorkohlensaureester einiger Oligoathylenglykole HO—(CH2CH2O)nH (n = 1–6) wurden mit Hexamethylendiamin, m-Toluylendiamin bzw. p-Phenylendiamin zu den entsprechenden Cyclodi-urethanen umgesetzt. Die Ausbeute in Abhangigkeit von der Ringgrose ergibt ein Maximum bei einer Ringgliederzahl von etwa 17. Ebenso wird die katalysierte Reaktion von Diisocyanaten mit Diolen zur Darstellung von Cyclo-urethanen benutzt. In Gegenwart von Di-n-butylzinndilaurat werden Austauschreaktionen sowohl zwischen Hydroxylendgruppen und Urethangruppen als auch zwischen Urethangruppen beobachtet. The bis-chlorocarbonates of some oligo-ethylene glycols HO—(CH2CH2O)nH (n = 1–6) were reacted with hexamethylene…
6-Amino-7-Azaindoles synthesis from 2,6-diamino pyridine and diols
2021
Abstract 6-Amino-7-azaindole has been prepared by combination of diaminopyridine and diols by means of an acceptorless dehydrogenative condensation. In addition, amino pyridines may also yield towards pyrrolo[3,2-b]pyrrole systems. All of these transformation have been performed with accessible heterogeneous catalysts: Pd/C and ZnO.
Efficient palladium catalyzed synthesis of heteroaromatic sulfoxides
2007
Abstract The present Letter describes the efficient synthesis of novel heteroaromatic sulfoxides by means of a palladium catalyzed heteroarylation of sulfenate anions. Triazolopyridine, pyridine and thiophene sulfoxides can be obtained under mild conditions and in high yield from the corresponding heteroaryl bromides.
Evidence for the Formation of a RuIII−RuIII Bond in a Ruthenium Corrole Homodimer
2000
Bedeutung von Assoziationsphänomenen quartärer Oniumverbindungen in der organischen Phase für den Ablauf phasentransferktalysierter Reaktionen
1980
Quartare Oniumsalze sind, wie dampfdruckosmometrische Messungen zeigen, in Benzol und Chloroform assoziiert [in Benzol starker (Faktor 4–15) als in Chloroform (Faktor 1.2 – 2.4)]. Im Homogen- und Zweiphasensystem laufen die Modellreaktionen (1) und (2) mit steigendem Assoziationsgrad schneller ab — langsamer im Zweiphasensystem wegen des Wassergehaltes der organischen Phase (Verminderung des Assoziationsgrades). Assoziationsphanomene sind offensichtlich fur die “Katalyse” im Zweiphasensystem wesentlich. Importance of Association Phenomena of Quaternary Onium Salts in the Organic Phase Responsible for the Course of Phase-Transfer-Catalysed Reactions As shown by vapour pressure osmometry quat…