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Ketene Acetals (ketene + acetal)
Kinds of Ketene Acetals Selected AbstractsConjugate Addition of a Silyl Ketene Acetal to ,,,-Unsaturated Lactones.CHEMINFORM, Issue 35 2006Rudhramyna Gnaneshwar Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Lewis Base Catalyzed, Enantioselective Aldol Addition of Methyl Trichlorosilyl Ketene Acetal to Ketones.CHEMINFORM, Issue 45 2005Scott E. Denmark Abstract For Abstract see ChemInform Abstract in Full Text. [source] The Mukaiyama,Michael Addition of a ,,,-Dimethyl Substituted Silyl Ketene Acetal to ,,,-Unsaturated Ketones Using Tetra-n-butylammonium Bibenzoate as a Nucleophilic Catalyst.CHEMINFORM, Issue 47 2003Rudhramyna Gnaneshwar Abstract For Abstract see ChemInform Abstract in Full Text. [source] Berichtigung: Palladium-Catalyzed ,-Arylation of ,,,-Unsaturated Esters from Silyl Ketene AcetalsANGEWANDTE CHEMIE, Issue 40 2010David No abstract is available for this article. [source] Palladium-Catalyzed ,-Arylation of ,,,-Unsaturated Esters from Silyl Ketene Acetals,ANGEWANDTE CHEMIE, Issue 33 2010David Smarter Katalysator: Eine Methode für die Palladium-katalysierte ,-Arylierung von ,,,-ungesättigten Estern wurde entwickelt, die über Silylketenacetale verläuft und ohne Fluorid-Aktivatoren auskommt. Die Kupplung gelingt mit elektronenreichen und elektronenarmen Aryl- und Vinylbromiden in hohen Ausbeuten, und andere funktionelle Gruppen werden gut toleriert. [source] ChemInform Abstract: Lewis Base Activation of Lewis Acids: Catalytic, Enantioselective Addition of Glycolate-Derived Silyl Ketene Acetals to Aldehydes.CHEMINFORM, Issue 42 2008Scott E. Denmark Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Reactions of Alkenyl Fischer Carbene Complexes with Ketene Acetals: Formation of Alkynes.CHEMINFORM, Issue 12 2007Siu Ling B. Wang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Uncatalyzed Reaction of Silyl Ketene Acetals with Oxalyl Chloride: A Straightforward Preparation of Symmetrical Pulvinic Acids.CHEMINFORM, Issue 29 2005Benoit Heurtaux No abstract is available for this article. [source] ChemInform Abstract: Sc(OTf)3 -Catalyzed Diastereoselective Addition of Enol Silanes and Silyl Ketene Acetals to Cr(CO)3 -Complexed Aryl Aldimines.CHEMINFORM, Issue 29 2002Bikash C. Maity Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Synthesis of 7,8-Benzo-9-aza-4-oxabicyclo[3.3.1]nonan-3-ones by Sequential "Condensation,Iodolactonization" Reactions of 1,1-Bis(trimethylsilyloxy)ketene Acetals with Isoquinolines.CHEMINFORM, Issue 14 2006Ehsan Ullah Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Facile Access to Optically Active Ferrocenyl Derivatives with Direct Substitution of the Hydroxy Group Catalyzed by Indium TribromideEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2007Paola Vicennati Abstract Ferrocene derivatives have found many different uses and applications in organometallic chemistry, material chemistry, and catalysis. We have shown that using a catalytic amount (5,10 mol-%) of commercially available indium tribromide, at room temperature, many carbon nucleophiles, such as indoles, allylsilane, enolsilane, silyl ketene acetal, diketone, and trimethylsilylcyanide, smoothly react with different optically active ferrocenyl alcohol derivatives to afford the desired products in high yield, with retention of configuration. Also, many different N-nucleophiles (azide, carbamates) and O-nucleophiles (alcohols) react as well, again with retention of configuration. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Mapping the characteristics of the radical ring-opening polymerization of a cyclic ketene acetal towards the creation of a functionalized polyesterJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2009Peter Plikk Abstract Radical ring-opening polymerization of cyclic ketene acetals is a means to achieve novel types of aliphatic polyesters. 2-methylene-1,3-dioxe-5-pene is a seven-membered cyclic ketene acetal containing an unsaturation in the 5-position in the ring structure. The double bond functionality enables further reactions subsequent to polymerization. The monomer 2-methylene-1,3-dioxe-5-pene was synthesized and polymerized in bulk by free radical polymerization at different temperatures, to determine the structure of the products and propose a reaction mechanism. The reaction mechanism is dependent on the reaction temperature. At higher temperatures, ring-opening takes place to a great extent followed by a new cyclization process to form the stable five-membered cyclic ester 3-vinyl-1,4-butyrolactone as the main reaction product. Thereby, propagation is suppressed and only small amounts of other oligomeric products are formed. At lower temperatures, the cyclic ester formation is reduced and oligomeric products containing both ring-opened and ring-retained repeating units are produced at higher yield. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4587,4601, 2009 [source] High-Speed Living Polymerization of Polar Vinyl Monomers by Self-Healing Silylium CatalystsCHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2010Dr. Yuetao Zhang Abstract This contribution describes the development and demonstration of the ambient-temperature, high-speed living polymerization of polar vinyl monomers (M) with a low silylium catalyst loading (, 0.05,mol,% relative to M). The catalyst is generated in situ by protonation of a trialkylsilyl ketene acetal (RSKA) initiator (I) with a strong Brønsted acid. The living character of the polymerization system has been demonstrated by several key lines of evidence, including the observed linear growth of the chain length as a function of monomer conversion at a given [M]/[I] ratio, near-precise polymer number-average molecular weight (Mn, controlled by the [M]/[I] ratio) with narrow molecular weight distributions (MWD), absence of an induction period and chain-termination reactions (as revealed by kinetics), readily achievable chain extension, and the successful synthesis of well-defined block copolymers. Fundamental steps of activation, initiation, propagation, and catalyst "self-repair" involved in this living polymerization system have been elucidated, chiefly featuring a propagation "catalysis" cycle consisting of a rate-limiting CC bond formation step and fast release of the silylium catalyst to the incoming monomer. Effects of acid activator, catalyst and monomer structure, and reaction temperature on polymerization characteristics have also been examined. Among the three strong acids incorporating a weakly coordinating borate or a chiral disulfonimide anion, the oxonium acid [H(Et2O)2]+[B(C6F5)4], is the most effective activator, which spontaneously delivers the most active R3Si+, reaching a high catalyst turn-over frequency (TOF) of 6.0×103,h,1 for methyl methacrylate polymerization by Me3Si+ or an exceptionally high TOF of 2.4×105,h,1 for n -butyl acrylate polymerization by iBu3Si+, in addition to its high (>90,%) to quantitative efficiencies and a high degree of control over Mn and MWD (1.07,1.12). An intriguing catalyst "self-repair" feature has also been demonstrated for the current living polymerization system. [source] Lewis Base Catalyzed Mannich-Type Reactions between Trimethylsilyl Enol Ethers and AldiminesCHEMISTRY - A EUROPEAN JOURNAL, Issue 19 2006Hidehiko Fujisawa Abstract Lewis base catalyzed Mannich-type reaction between trimethylsilyl enol ethers and N -tosylaldimines is described. Nitrogen anions generated from amides or imides such as lithium benzamide or potassium phthalimide are found to be effective Lewis base catalysts in DMF at room temperature to afford the corresponding ,-amino carbonyl compounds in good to high yields; the oxygen anion generated from carboxylic acids such as lithium acetate was also found to be effective in dry DMF. The above-mentioned lithium acetate-catalyzed Mannich-type reaction between aldimines and various trimethylsilyl (TMS) enol ethers such as silyl ketene acetal proceeded smoothly even in water-containing DMF. Then, Lewis base catalyzed three-component Mannich-type reactions of TMS enol ether, tosylamide, and aromatic aldehyde having electron-withdrawing group such as p -nitrobenzaldehyde were investigated. The reaction proceeded smoothly to afford the corresponding ,-amino ester in good yield. Further, ammonium carboxylates such as tetrabutyl ammonium acetate or tetrabutyl ammonium benzoate were found to be more effective Lewis base catalysts in the above-mentioned Mannich-type reaction. The synthesis proceeded in various solvents at lower temperatures. The reaction between aldimines and TMS enol ethers generated from thioester and various ketones such as propiophenone or cyclohexanone also proceeded smoothly to afford the corresponding ,-amino carbonyl compounds in high yields with good to high anti -selectivities. [source] Improved Synthesis of Pyrroles and Indoles via Lewis Acid-Catalyzed Mukaiyama,Michael-Type Addition/Heterocyclization of Enolsilyl Derivatives on 1,2-Diaza-1,3-Butadienes.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2007Role of the Catalyst in the Reaction Mechanism Abstract The Mukaiyama,Michael-type addition of various silyl ketene acetals or silyl enol ethers on some 1,2-diaza-1,3-butadienes proceeds at room temperature in the presence of catalytic amounts of Lewis acid affording by heterocyclization 1-aminopyrrol-2-ones and 1-aminopyrroles, respectively. 1-Aminoindoles have been also obtained by the same addition of 2-(trimethylsilyloxy)-1,3-cyclohexadiene on some 1,2-diaza-1,3-butadienes and subsequent aromatization. Mechanistic investigations indicate the coordination by Lewis acid of the enolsilyl derivative and its 1,4-addition on the azo-ene system of 1,2-diaza-1,3-butadienes. The migration of the silyl group from a hydrazonic to an amidic nitrogen, its acidic cleavage and the final internal heterocyclization give the final products. Based on NMR studies and ab initio calculations, a plausible explanation for the migration of the silyl protecting group is presented. [source] Reactivity parameters for rationalizing iminium-catalyzed reactions,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 10 2010Sami Lakhdar Abstract The correlation equation (1), lg k(20,°C),=,s(E,+,N), where electrophiles are characterized by one (E) and nucleophiles are characterized by two parameters (N, s) was used to rationalize the scope of iminium-catalyzed reactions. Kinetics of the reactions of iminium triflates, pregenerated from cinnamaldehyde and secondary amines, with cyclic ketene acetals were studied by UV,Vis spectroscopy. From the second-order rate constants, electrophilicity parameters ,10,<,E,<,,7 have been derived for these iminium ions. Eqn (1) was found to correctly predict the rate constants for the reactions of the cinnamaldehyde-derived iminium ions with pyrroles, indoles, and sulfur ylides. The zwitterion obtained from cinnamaldehyde and indoline-2-carboxylic acid reacts more than 105 times faster with a sulfur ylide than predicted by Eqn (1), which is explained by MacMillan's ,electrostatic activation'. The failure of imidazolidinones to catalyze cyclopropanations of ,,,-unsaturated carbonyl compounds by sulfur ylides is not due to the low nucleophilic reactivity of sulfur ylides but due to their high Brønsted basicity which inhibits the formation of the iminium ions. Copyright © 2010 John Wiley & Sons, Ltd. [source] Mapping the characteristics of the radical ring-opening polymerization of a cyclic ketene acetal towards the creation of a functionalized polyesterJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2009Peter Plikk Abstract Radical ring-opening polymerization of cyclic ketene acetals is a means to achieve novel types of aliphatic polyesters. 2-methylene-1,3-dioxe-5-pene is a seven-membered cyclic ketene acetal containing an unsaturation in the 5-position in the ring structure. The double bond functionality enables further reactions subsequent to polymerization. The monomer 2-methylene-1,3-dioxe-5-pene was synthesized and polymerized in bulk by free radical polymerization at different temperatures, to determine the structure of the products and propose a reaction mechanism. The reaction mechanism is dependent on the reaction temperature. At higher temperatures, ring-opening takes place to a great extent followed by a new cyclization process to form the stable five-membered cyclic ester 3-vinyl-1,4-butyrolactone as the main reaction product. Thereby, propagation is suppressed and only small amounts of other oligomeric products are formed. At lower temperatures, the cyclic ester formation is reduced and oligomeric products containing both ring-opened and ring-retained repeating units are produced at higher yield. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4587,4601, 2009 [source] | ||||||||||||||||||||||