Search results for "Imine"
showing 10 items of 2850 documents
In situ formation of steroidal supramolecular gels designed for drug release
2013
In this work, a steroidal gelator containing an imine bond was synthesized, and its gelation behavior as well as a sensitivity of its gels towards acids was investigated. It was shown that the gels were acid-responsive, and that the gelator molecules could be prepared either by a conventional synthesis or directly in situ during the gel forming process. The gels prepared by both methods were studied and it was found that they had very similar macroand microscopic properties. Furthermore, the possibility to use the gels as carriers for aromatic drugs such as 5-chloro-8-hydroxyquinoline, pyrazinecarboxamide, and antipyrine was investigated and the prepared two-component gels were studied with…
Organocatalytic enantioselective aminoalkylation of pyrazol-3-ones with aldimines generated in situ from α-amido sulfones
2019
Herein, an efficient asymmetric aminoalkylation of pyrazolones with α-amido sulfones catalyzed by a quinine-derived squaramide in dichloromethane/aqueous media has been established. A variety of chiral amines were obtained with high yields (up to 98%) and excellent enantioselectivities (up to 99% ee). The corresponding products are transformed into optically active acetylated pyrazoles after treatment with Ac2O/Et3N, because of the instability of some adducts. The reaction tolerates a wide range of α-amido sulfones and different pyrazolones.
Enantioselective zinc/BINOL-catalysed alkynylation of aldimines generated in situ from α-amido sulfones.
2012
Chiral nonracemic N-Cbz-protected propargylic amines have been prepared by the addition of terminal alkynes to imines generated in situ from α-amido sulfones in the presence of diethylzinc and BINOL-type ligands as catalysts. The reactions give good yields and high enantioselectivities (ee values up to 95 %) for a good number of aromatic and heteroaromatic α-amido sulfones and alkynes.
Pedagogical experiments with MathCheck in university teaching
2019
MathCheck is a relatively new online tool that gives students feedback on their solutions to elementary university mathematics and theoretical computer science exercises. MathCheck was designed with constructivism learning theory in mind and it differs from other online tools as it checks the solutions step by step and shows a counter-example if the step is incorrect. It has been in student use since the autumn of 2015 and under design-based research from the first online day. The main research questions of this study are the following. 1) How can the usage of MathCheck support the aspects of conceptual understanding and procedural fluency of constructivism learning? 2) How can MathCheck em…
Self‐Directed Learning in Creative Activity : An Ethnographic Study in Technology‐Based Work
2020
Under conditions of rapid changes in working life, there is an urgent need to examine the nature of creativity and learning in organizations. The aim of this study was to investigate the nature of self‐directed learning (SDL) practices in creative activity in technology‐based work. We focus on both individual and collective practices but also on the importance of organizational culture. The data consist of 46 interviews and observational field notes collected from participating organizations. Thematic and ethnographic analyses were utilized as tools to reveal the nature of SDL in creative activity. We found three themes describing of the nature of SDL in creative activity: a combination of …
Organocatalytic Enantioselective Friedel–Crafts Aminoalkylation of Indoles in the Carbocyclic Ring
2016
The first general catalytic method for the, so far elusive, enantioselective Friedel−Crafts functionalization of indoles in the carbocyclic ring is presented. This transformation contrasts with the usual tendency of these heterocycles to react at the azole ring. For this purpose, the four regioisomeric hydroxy carbocyclic-substituted indoles were reacted with several isatinderived ketimines, using a Cinchona alkaloid-based squaramide, in a low 0.5−5 mol % catalyst loading, as a bifunctional catalyst. This methodology allows the functionalization of indoles in every position of the carbocyclic ring in a regio- and enantioselective fashion, by switching only the position of the hydroxy group …
Parlons sécurité
2012
National audience; Les questions de sécurité publique sont au cœur de l’actualité française. En témoignent les lois d'orientation et de programmation pour la performance de la sécurité intérieure (dites LOPSI 1 et LOPPSI 2), le débat autour du fichier central d’identité biométrique ou encore celui sur la vidéosurveillance et les violences urbaines avec l’exemple anglais. Quels sont les enjeux et les réalités de la sécurité en France ? Pour sortir du brouhaha médiatique, « Entrez dans l’actu » vous présente l’éventail des informations en mesure de vous éclairer objectivement.
Magnetic coupling and spin topology in linear oxalato-bridged tetranuclear chromium(III)–copper(II) complexes with aromatic diimine ligands
2013
Abstract A novel heterotetranuclear chromium(III)–copper(II) complex of formula {[CrIII(bpy)(ox)2]2CuII2(bpy)2(ox)}·6H2O (1) has been synthesized by the ligand exchange reaction between Ph4P[CrIII(bpy)(ox)2]·H2O and [CuII(bpy)2(NO3)]NO3·MeOH in methanol (bpy = 2,2′-bipyridine; ox2− = oxalate dianion). The X-ray crystal structure of 1 consists of neutral oxalato-bridged CrIII2Cu2II zigzag entities which are formed by the monodentate coordination of two [CrIII(bpy)(ox)2]− mononuclear anionic units through one of its two oxalato groups toward a [CuII2(bpy)2(ox)]2+ dinuclear cationic moiety featuring relatively long axial bonds at the square pyramidal CuII ions. Variable temperature (2.0–300 K)…
Reactions of (η5-C5H5)(CO)2Fe-Substituted N-Sulfonyl Azadienes with C-Nucleophiles. A Route to 5-Substituted Dihydropyrrolones
2000
A variety of cyclic β-[(η5-C5H5)(CO)2Fe]-substituted N-sulfonyl azadienes 4 were prepared: e.g., from the corresponding iron-substituted (Z)-enals and benzenesulfonamide. Reactions of these iron compounds with Grignard reagents or organolithiums gave 5-substituted α,β-unsaturated N-sulfonyl γ-lactams 5. In some cases the corresponding non-N-protected 5-substituted γ-lactams 6 were isolated as well. Key steps of these reaction cascades are the initial 1,2-addition to the imine moiety and the subsequent carbonylation step. The reaction of the chromene−iron complex 4e with (allyl)MgCl gave the (η3-allyl)iron−γ-lactam complex 8a with a ring-opened chromene framework. This complex was structura…
Cycloadditionen von 2H ‐Benzo[ b ]thiet und Verbindungen mit kumulierten Doppelbindungen
1994
Cycloaddition Reactions of 2H-Benzo[b]thiete and Compounds with Cumulated Double Bonds o-Thiobenzoquinone methide (2), generated by thermal ring opening of 2H-benzo[b]thiete (1), reacts with allene 3, ketene imine 7, the carbodiimides 9a-c, and the N-sulfinylamines 11a-c in highly specific [8π + 2π] cycloaddition processes to form novel types of heterocyclic systems 4, 8, 10a-c, and 12a-c with exocyclic double bonds. The 1:1 adduct 4 can add a further molecule of allene to yield the spiro compounds 5 and 6.