Search results for "Reaction"
showing 10 items of 6134 documents
ChemInform Abstract: Reactions of 3-Vinylindole Derivatives with Dienophiles.
2010
Reactions of 3-(1-cyclohexenyl)-1,2-dimethylindole (1a) and the 1,2-dihydrocarbazole 1b with some carbo- and heterodienophiles are described. Thus, compound 1a reacts to give ene, Michael-type, and Diels-Alder adducts, depending on the dienophile and reaction conditions. The 3-vinylindole 1b reacts with 4-phenyl-1,2,4-triazoline-3,5-dione or N-phenylmaleimide in a dehydrogenative reaction to yield the fully aromatized carbazole 8.
Synthesis of Optically Pure Arylamine Derivatives by Using the Bucherer Reaction
2017
The Bucherer reaction is a common pathway for the conversion of 1- and 2-naphthols into the corresponding 1- or 2-naphthylamines, respectively. Mostly, only singular examples for its preparative use are reported since this particular transformation seems to be very sensitive to the reaction conditions. By choosing different phenolic substrates and chiral amines, we were able to prepare a broad scope of optically pure arylamines using this type of reaction. In contrast to alternative methods forming C−N aryl bonds such as Buchwald-Hartwig or Chan-Lam cross-coupling reactions, no palladium or copper catalysts are required. The use of water as solvent and the easily available starting material…
Palladium-Catalyzed N-Arylation Reactions with Aziridine and Azetidine
2007
Studies on the viability of palladium-catalyzed cross-coupling reactions of aryl- or hetaryl bromides with the parent aziridine or azetidine showed that a wide range of N-arylaziridines and N-arylazetidines are accessible by this method. Ring cleavage of the N-arylaziridines or -azetidines thus produced does not occur under the applied reaction conditions. The synthetic utility of the method is illustrated by examples of double N-arylations with either aziridine or azetidine.
Synthese und eigenschaften von einem nitrosubstituierten p-polyphenylen und von nitrosubstituierten p-oligophenylenen. 15. Mitteilung1
1964
Bei aromatischen Nitrojodverbindungen nimmt die ULLMANN-Reaktion unter verhaltnismasig milden Bedingungen einen praktisch quantitativen Verlauf, wenn sich das Jod in der o-Stellung zu einer Nitrogruppe befindet. Mit einer entsprechenden bifunktionellen Verbindung, dem 4,4′-Dijod-3,3′-dinitrobiphenyl, konnte unter den gleichen Bedingungen ein nitrosubstituiertes p-Polyphenylen erhalten werden, ein hellgelbes, unlosliches und unschmelzbares Pulver, das sich bei hoherer Temperatur (> 250°C) zersetzt. Auf Grund des Jodgehaltes (Endgruppen) wurde ein mittlerer Kondensationsgrad von 52 berechnet; das entspricht einer p-Phenylenkette aus 104 Benzolringen. Das Polymere ist kristallin und besitzt ei…
On the mechanism of the addition of organolithium reagents to cinnamic acids
2001
Abstract The regioselectivity of the addition of tert-butyllithium to cinnamic acid is subject to reaction conditions and to substituent electronic effects. Significant effects are observed in the presence of several additives including a radical trap such as α-methylstyrene. Competition experiments by addition of the organolithium reagent to mixtures of substituted cinnamic acids show that the relative rates of both conversion of the starting acids and formation of the 1,3-adducts are subject to electronic effects, whereas rates for 1,4-addition are independent of the substituents. These features are in agreement with a polar addition mechanism, but a fast SET equilibrium followed by slow …
The effect of trivalent framework heteroatoms in Cu-CHA on the Selective Catalytic Reduction of NO
2021
Abstract The effect of the trivalent framework atoms (Si4+/M3+ = 13-105) in Cu exchanged CHA-type zeolites was investigated for the selective catalytic reduction of NO with NH3. While the increased hydrophobicity of B-CHA compared to Al-CHA could make it a good candidate for low temperature SCR, the material was too unstable under reaction conditions and the exchanged Cu2+ did not remain isolated. Consequently a lower activity and selectivity than for Al-CHA were observed. Ga-CHA on the other hand showed a similar Cu2+ speciation as Al-CHA at similar Si4+/M3+ ratios. The difference in catalytic activity was remarkably small. While Ga-CHA was less stable upon hydrothermal aging, this was mar…
PHOSPHORORGANISCHE VERBINDUNGEN 115 WEGE ZUM ANALYTISCHEN NACHWEIS VON VERBINDUNGEN MIT DER P(O)F- UND P(O)SR-GRUPPE
1984
Abstract Acridine-9-hydroxamicacid 5 is suitable for the analytical detection of the model phosphorylfluorides 7 by fluorescence. The model compounds are rearranged according to Lossen and degradated to the fluorescent 9-aminoacridine 6 using defined reaction conditions. Thiophospho-S-esters (with diethyl-thiophosphinicacid-S-butylester 8 as a model compound) are cleaved to the corresponding phosphoryl-fluorides (a) and mercaptanes (b) by fluorolysis. (a) is identified qualitatively with acridine-9-hydroxamicacid 5, (b) by the Ellman-reaction. Zum Fluoreszenznachweis der Modellphosphorylfluoride 7 ist Acridin-9-hydroxamsaure 5 geeignet. Die Modellverbindungen 7 werden unter Einhaltung defin…
First Fluorous Synthesis of Fluorinated Uracils
2006
This paper describes a novel fluorous synthesis of fluorinated uracils 4. In this new protocol, fluorous alcohols 1, which are used as fluorous tags, are acetylated to yield acetates 2, which in turn are treated with a base to form their enolates. These are then reacted with fluorinated nitriles to furnish tagged β-enamino esters 3. Although this condensation step had been performed easily in previous solution and solid-phase syntheses, it proved to be very elusive in the fluorous version. Meticulous control of the reaction conditions was thus essential in order to achieve satisfactory yields of β-enamino esters 3. The final treatment of compounds 3 with isocyanates or isothiocyanates effic…
Efficient flow injection and sequential injection methods for spectrophotometric determination of oxybenzone in sunscreens based on reaction with Ni(…
2001
Spectrophotometric determination of a widely used UV-filter, such as oxybenzone, is proposed. The method is based on the complexation reaction between oxybenzone and Ni(II) in ammoniacal medium. The stoichiometry of the reaction, established by the Job method, was 1:1. Reaction conditions were studied and the experimental parameters were optimized, for both flow injection (FI) and sequential injection (SI) determinations, with comparative purposes. Sunscreen formulations containing oxybenzone were analyzed by the proposed methods and results compared with those obtained by HPLC. Data show that both FI and SI procedures provide accurate and precise results. The ruggedness, sensitivity and LO…
Understanding phenolic acids inhibition of α-amylase and α-glucosidase and influence of reaction conditions
2022
Phenolic acids are involved in modulating the activity of starch digestive enzymes but remains unclear if their interaction with enzymes or starch is governing the inhibition. The potential inhibition of nine phenolic acids against α-amylase and α-glucosidase was studied applying different methodologies to understand interactions between phenolic acids and either enzymes or substrates. Vanillic and syringic acids were prone to interact with α-amylase requiring low half-maximum inhibitory concentration (IC50) to inhibit starch hydrolysis. Nevertheless, the initial interaction of phenolic acids with starch somewhat obstructed their interaction with starch, requiring 10 times higher IC50, with…