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Cycloisomerization Reactions (cycloisomerization + reaction)
Selected AbstractsChemInform Abstract: Au(I)-Catalyzed Cycloisomerization Reaction of Amide- or Ester-Tethered 1,6-Enynes to Bicyclo[3.2.0]hept-6-en-2-ones.CHEMINFORM, Issue 11 2010Young Tak Lee 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] ChemInform Abstract: Platinum-Catalyzed Cycloisomerization Reaction of 1,6-Enyne Coupling with Rearrangement of Propargylic Esters.CHEMINFORM, Issue 17 2009Li Lu 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] 2,3,4- or 2,3,5-Trisubstituted Furans: Catalyst-Controlled Highly Regioselective Ring-Opening Cycloisomerization Reaction of Cyclopropenyl Ketones.CHEMINFORM, Issue 7 2004Shengming Ma No abstract is available for this article. [source] Gold-Catalyzed Cycloisomerization Reactions of 2-Tosylaminophenylprop-1-yn-3-ols as a Versatile Approach for Indole Synthesis,ANGEWANDTE CHEMIE, Issue 27 2010Prasath Kothandaraman Gold und Indole: Die Titelreaktion verläuft vermutlich über ein Vinyl-Gold-Intermediat, das in,situ durch Einwirkung von AuCl/AgOTf entsteht. Unter den Reaktionsbedingungen werden Inden-anellierte und 2,3-disubstituierte Indolderivate in Ausbeuten bis 94,% erhalten (siehe Schema). [source] ChemInform Abstract: Synthesis of 2-Thio- and 2-Oxoimidazoles via Cascade Addition,Cycloisomerization Reactions of Propargylcyanamides.CHEMINFORM, Issue 18 2010Robert L. Giles 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] Platinum- and Gold-Catalyzed Cycloisomerization Reactions of Hydroxylated Enynes.CHEMINFORM, Issue 46 2004Victor Mamane Abstract For Abstract see ChemInform Abstract in Full Text. [source] ,6 -Mesityl,, 1 -Imidazolinylidene,Carbene,Ruthenium(II) Complexes: Catalytic Activity of Their Allenylidene Derivatives in Alkene Metathesis and Cycloisomerization Reactions.CHEMINFORM, Issue 38 2003Bekir Cetinkaya Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Platinum-Catalyzed Cycloisomerization Reactions of Enynes.CHEMINFORM, Issue 17 2002Alois Fuerstner 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] Platinum- and Gold-Catalyzed Rearrangement Reactions of Propargyl Acetates: Total Syntheses of (,)-,-Cubebene, (,)-Cubebol, Sesquicarene and Related TerpenesCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2006Alois Fürstner Prof. Abstract Propargyl acetates, in the presence of catalytic amounts of late transition-metal salts such as PtCl2 or AuCl3, represent synthetic equivalents of ,-diazoketones. This notion is corroborated by a concise approach to various sesquiterpene natural products starting from readily available substrates. Specifically, (+)-carvomenthone (17) is converted into propargyl acetate (S)- 26 by a sequence involving Stille cross-coupling of its kinetic enol triflate 18, regioselective hydroboration/oxidation of the resulting 1,3-diene 19, and addition of an alkynyl cerium reagent to aldehyde 21 thus obtained. Since the latter step was found to be unselective, the configuration of the reacting propargyl acetate was unambiguously set by oxidation followed by diastereoselective transfer hydrogenation by using Noyori's catalyst 25. Compound (S)- 26, on treatment with PtCl2 in toluene, converted exclusively to the tricyclic enol acetate 27, which was saponified to give norcubebone 11 in excellent overall yield. The conversion of this compound into the sesquiterpene alcohol (,)-cubebol (6) was best achieved with MeCeCl2 as the nucleophile, whereas the formation of the parent hydrocarbon (,)-,-cubebene (4) was effected in excellent yield by recourse to iron-catalyzed cross coupling methodology developed in this laboratory. Since norketone 11 has previously been transformed into (,)-,-cubebene (5) as well as (,)-4-epicubebol 8, our approach constitutes formal total syntheses of these additional natural products as well. Along similar lines, the readily available propargyl acetates 1, 33 and 47 were shown to give access to 2-carene 44, sesquicarene 39, and episesquicarene 51 in excellent overall yields. In this series, however, the cycloisomerization reaction was best achieved with catalytic amounts of AuCl3 in 1,2-dichloroethane as the solvent. In addition to these preparative results, our data provide some insight into the mechanism of these remarkable skeletal rearrangement reactions. Transformations of this type are likely triggered by initial coordination of the alkyne unit of the substrate to the carbophilic transition-metal cation. Formal attack of the alkene moiety onto the resulting ,-complex engenders the formation of an electrophilic cyclopropyl carbene species which subsequently reacts with the adjacent acetate unit to give the final product. The alternative phasing of events, implying initial attack of the acetate (rather than the alkene moiety) onto the metal,alkyne complex, is inconsistent with the stereochemical data obtained during this total synthesis campaign. [source] Synthesis of Substituted 1,3-Diene Synthetic Equivalents by a Ru-Catalyzed Diyne Hydrative CyclizationCHEMISTRY - AN ASIAN JOURNAL, Issue 3 2006Barry Abstract Catalyzed by [CpRu(CH3CN)3]PF6, the hydrative cyclization of dipropargylic sulfone substrates provides an effective way to synthesize highly functionalized substituted 3-sulfolenes. The amount of water is crucial for the reactivity of this cycloisomerization reaction. The scope and limitations of the Ru-catalyzed cycloisomerization are discussed. A marked ketone-directing effect was observed for the first time in ruthenium-catalyzed cyclizations. A plausible mechanism for the ketone-directed cycloisomerization is also rationalized. The utility of this method was demonstrated by both sulfur dioxide extrusion of the 3-sulfolenes to afford 1,3-dienes and subsequent inter- or intramolecular Diels,Alder reactions. [source] An Efficient Domino Approach for the Synthesis of Multisubstituted Pyrroles via Gold/Silver-Catalyzed Amination/Cycloisomerization of (Z)-2-En-4-yn-1-olsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Yuhua Lu Abstract An efficient and one-pot synthesis of multisubstituted pyrroles with high diversity and in a regioselective manner from the reactions of suitably substituted (Z)-enynols with amines or sulfonamides under mild reaction conditions has been developed. This synthesis was realized via a cascade process in the presence of gold/silver (Au/Ag) or boron trifluoride,etherate/gold/silver (BF3,Et2O/Au/Ag) catalysts, which could catalyze amination and cycloisomerization reactions in the same vessel. [source] Synthesis of (,)-Cubebol by Face-Selective Platinum-, Gold-, or Copper-Catalyzed Cycloisomerization: Evidence of Chirality Transfer and Mechanistic InsightsCHEMISTRY - A EUROPEAN JOURNAL, Issue 38 2009Charles Fehr Dr. Abstract We describe in detail a direct, stereoselective synthesis of (,)-cubebol based on a Pt-, Au-, or Cu-catalyzed cycloisomerization in which control of the configuration of the propargylic center is essential for the facial selectivity. In addition, we show that cycloisomerization reactions of enantioenriched propargyl pivalates occur with substantial chirality transfer. We confirm a mechanism by means of cyclization followed by an [1,2]-acyl migration for the Pt- and the Au-catalyzed cycloisomerization. So far, no evidence supports that the Cu-catalyzed cycloisomerization follows the same reaction course. [source] Silver versus Gold Catalysis in Tandem Reactions of Carbonyl Functions onto Alkynes: A Versatile Access to Furoquinoline and Pyranoquinoline CoresCHEMISTRY - A EUROPEAN JOURNAL, Issue 19 2007Thomas Godet Abstract An efficient and versatile tandem process of acetalization and cycloisomerization reactions has been developed for the reactions of 1-alkynyl-2-carbonylquinoline substrates. The reaction occurs thanks to AuI and AgI catalysis. Silver(I) catalysis has been extensively studied (11 different silver species) on a broad range of quinoline derivatives (variation of alkyne substituent, of carbonyl function and of nucleophiles), leading to a variety of furoquinoline and pyranoquinoline moieties. An insight is given for the presumed mechanism along with DFT-B3,LYP/6,31G** calculations to address the 6- endo and 5- exo regioselectivities observed. [source] | ||||||||||||||||||||||