Un article de Wikipédia, l'encyclopédie libre. In chemistry, an ester is a chemical compound derived from an acid in which at least one –OH (hydroxyl) group is replaced by an –O–alkyl (alkoxy) group. Dernière modification le 6 février 2019, à 22:53. Dabei bildet sich das durch Keto-Enol-Tautomerie stabilisierte Carbanion 2, welches nach der Abspaltung des Halogenidions in das Cyclopropanon-Intermediat 3 übergeht. Es entsteht die Verbindung 4, die nach einer Umlagerung durch ein Wassermolekül protoniert wird. The Favorskii rearrangement, named for the Russian chemist Alexei Yevgrafovich Favorskii, is most principally a rearrangement of cyclopropanones and α-halo ketones which leads to carboxylic acid derivatives. The source code for the WIKI 2 extension is being checked by specialists of the Mozilla Foundation, Google, and Apple. Während diese Umlagerung beim Chlorcyclopentanon nicht bekannt ist, liefert 2-Halogencyclobutanon 12 unter Ringverengung die Cyclopropancarbonsäure 14, neben 2-Hydroxycyclobutanon und stellt ein Beispiel für den beschriebenen Mechanismus dar. La dernière modification de cette page a été faite le 6 février 2019 à 21:54. Cet énolate se cyclise en un intermédiaire cyclopropanone qui est ensuite attaqué par l'hydroxyde qui joue le rôle de nucléophile. In the case of cyclic α-halo ketones, the Favorski rearrangement constitutes a ring contraction It is often used for the coupling of amino acids for peptide synthesis and as a reagent in organic synthesis. The reaction was discovered in the early 1900s by the Russian chemist Alexei Yevgrafovich Favorskii. In the related Wallach degradation (Otto Wallach, 1918) not one but two halogen atoms flank the ketone resulting in a new contracted ketone after oxidation and decarboxylation [9] [10]. This enolate cyclizes to a cyclopropanone intermediate which is then attacked by the hydroxide nucleophile. In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group -COCl. It will enhance any encyclopedic page you visit with the magic of the WIKI 2 technology. Shiina esterification is an organic chemical reaction that synthesizes carboxylic esters from nearly equal amounts of carboxylic acids and alcohols by using aromatic carboxylic acid anhydrides as dehydration condensation agents. The second step has also been proposed to be stepwise process, with chloride anion leaving first to produce a zwitterionic oxyallyl cation before a disrotatory electrocyclic ring closure takes place to afford the cyclopropanone intermediate.[9]. Elle a été découverte au début des années 1900 par le chimiste russe Alexei Yevgrafovich Favorskii[1]. In the case of cyclic α-halo ketones, the Favorskii rearrangement constitutes a ring contraction. This rearrangement takes place in the presence of a base, sometimes hydroxide, to yield a carboxylic acid but most of the time either an alkoxide base or an amine to yield an ester or an amide, resp… In the related Wallach degradation (Otto Wallach, 1918) not one but two halogen atoms flank the ketone resulting in a new contracted ketone after oxidation and decarboxylation[10][11], The reaction type also exists as a photochemical reaction. Die Faworski-Umlagerung (oft Favorskii-Umlagerung geschrieben, englisch Favorskii rearrangement) ist eine Namensreaktion in der organischen Synthesechemie, die nach dem russischen Chemiker Alexei Jewgrafowitsch Faworski (1860–1945) benannt wurde. The photo-Favorskii reaction has been used in the photochemical unlocking of certain phosphates (for instance those of ATP) protected by so-called p-hydroxyphenacyl groups. Sobenina, Tomilin, Petrova et Mikhaleva, «, 10.1002/(SICI)1099-0690(199901)1999:1<277::AID-EJOC277>3.0.CO;2-R, https://fr.wikipedia.org/w/index.php?title=Réaction_de_Favorskii&oldid=156529547, Réaction formant une liaison carbone-carbone, licence Creative Commons attribution, partage dans les mêmes conditions, comment citer les auteurs et mentionner la licence. They are exclusively synthetic. This enolate cyclizes to a cyclopropanone intermediate which is then attacked by the hydroxide nucleophile. Nitrate esters, such as nitroglycerin, are known for their explosive properties, while polyesters are important plastics, with monomers linked by ester moieties. Nucleophilic acyl substitution describe a class of substitution reactions involving nucleophiles and acyl compounds. Lorsque le carbonyle est un aldéhyde (R"=H), un réarrangement se produit et conduit à une énone. I am just editing the German article on the de:Faworski-Reaktion and am somewhat surprised that here Favorskii reaction and Favorskii rearrangement are given as synonymes for what is the German de:Faworski-Umlagerung.Why is the reaction involving an alkyne and a carbonyl moiety omitted in the English Wikipedia, while it is well present in English chemical literature? Favorskii rearrangement mechanism.png 1,649 × 520; 22 KB. The name may also refer to the specific compound ethenone H2C=C=O, the simplest ketene. A characteristic is the formal uptake of water generated in the reaction by DCC, forming the urea compound dicyclohexylurea (DCU). Cette réaction est utilisée pour protéger les alcynes : l'alcyne est soit converti grâce à l'acétone en 2-hydroxyprop-2-yl-alcyne ou un alcyne protégé peut être synthétisé directement à l'aide du 2-méthyl-but-3-yn-2-ol disponible dans le commerce comme source d'alcyne[4]. The reaction was first described by Wolfgang Steglich in 1978. Lorsque le carbonyle est un aldéhyde, un réarrangement se produit et conduit à une énone.


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