Showing papers on "Annulation published in 2005"
TL;DR: The first highly enantioselective variant of the Kwon annulation of imines with allenes is described, and C2-symmetric chiral phosphepine 1 serves as an effective catalyst for this powerful process, furnishing an array of functionalized piperidine derivatives with very good stereoselectivity.
Abstract: Although tertiary phosphines have emerged as remarkably versatile nucleophilic catalysts, there has been only very limited progress in achieving asymmetric catalysis with chiral phosphines. In this report, the first highly enantioselective variant of the Kwon annulation of imines with allenes is described. Thus, C2-symmetric chiral phosphepine 1 serves as an effective catalyst for this powerful process, furnishing an array of functionalized piperidine derivatives with very good stereoselectivity.
343 citations
TL;DR: A rhenium complex, [ReBr(CO)3(thf)]2, catalyzes the reaction of an aromatic aldimine with an acetylene to give an indene derivative in a quantitative yield via C-H bond activation, insertion of the acetylene, intramolecular nucleophilic cyclization, and reductive elimination.
Abstract: A rhenium complex, [ReBr(CO)3(thf)]2, catalyzes the reaction of an aromatic aldimine with an acetylene to give an indene derivative in a quantitative yield. The reaction proceeds via C-H bond activation, insertion of the acetylene, intramolecular nucleophilic cyclization, and reductive elimination. In contrast to ruthenium and rhodium catalysts, which are usually employed in this type of reaction, the rhenium catalyst promotes the intramolecular nucleophilic cyclization of the alkenylmetal species generated by insertion of the acetylene.
226 citations
TL;DR: An application of the phosphine-catalyzed [4 + 2] annulation in the formal synthesis of alstonerine and macroline is reported, which formed the D ring of the target indole alkaloids.
204 citations
TL;DR: A novel phosphine-catalyzed reaction of modified allylic compounds, including acetates, bromides, chlorides, or tert-butyl carbonates derived from the Morita-Baylis-Hillman (MBH) reaction with tropone to yield [3+6] annulation products in excellent yields was developed.
179 citations
TL;DR: The Pd-catalyzed annulation of arynes by 2-halobiaryls and related vinylic halides provides a very efficient, high yielding synthesis of polycyclic aromatic and heteroaromatic hydrocarbons.
Abstract: The Pd-catalyzed annulation of arynes by 2-halobiaryls and related vinylic halides provides a very efficient, high yielding synthesis of polycyclic aromatic and heteroaromatic hydrocarbons. This process appears to involve the catalytic, stepwise coupling of two very reactive substrates, an aryne and an organopalladium species, to generate excellent yields of cross-coupled products.
163 citations
TL;DR: A novel [5 + 1] annulation strategy is developed for the synthesis of highly substituted phenols and cyclohexenones from alpha-alkenoyl ketenedithioacetals and nitroalkanes.
Abstract: A novel [5 + 1] annulation strategy is developed for the synthesis of highly substituted phenols and cyclohexenones from α-alkenoyl ketenedithioacetals and nitroalkanes.
161 citations
TL;DR: In this article, a novel [5 + 1] annulation strategy was developed for the synthesis of highly substituted phenols and cyclohexenones from α-alkenoyl ketenedithioacetals and nitroalkanes.
Abstract: A novel [5 + 1] annulation strategy is developed for the synthesis of highly substituted phenols and cyclohexenones from α-alkenoyl ketenedithioacetals and nitroalkanes
148 citations
TL;DR: A new [3 + 2] annulation reaction was developed in which 2-cyanophenylboronic acid reacted as a three-carbon component with alkynes or alkenes to afford substituted indenones or indanones.
141 citations
TL;DR: Examination of the regiochemistry of isoquinolines synthesized indicates that there are two different alkyne insertion pathways for the catalytic reactions.
127 citations
TL;DR: A strategy for the synthesis of polycyclic aromatic hydrocarbons by the ring-closing olefin metathesis (RCM) of pendant olefins on a phenylene backbone has been developed and is an effective and general method for the preparation of PAHs.
Abstract: A strategy for the synthesis of polycyclic aromatic hydrocarbons (PAHs) by the ring-closing olefin metathesis (RCM) of pendant olefins on a phenylene backbone has been developed. RCM of 2,4',6',2' '-tetravinyl-[1,1';3',1' ']terphenyl and 2,2',5',2' '-tetravinyl-[1,1';4',1']terphenyl affords in high yield the isomeric [a,j] and [a,h] dibenzanthracenes, respectively. In contrast with other intramolecular annulation methods, such as Friedel-Crafts acylations, this reaction is completely regioselective. Since RCM is reversible and PAHs are often thermodynamic sinks, this strategy is an effective and general method for the preparation of PAHs. Density functional theory calculations support these results. Carbon disulfide is a suitable solvent for these reactions.
112 citations
TL;DR: A new three-component cyclization-coupling reaction catalyzed by palladium was developed, producing polysubstituted furans in good yields from readily available substrates.
Abstract: A new three-component cyclization-coupling reaction catalyzed by palladium was developed, producing polysubstituted furans in good yields from readily available substrates. The reaction conditions and the scope of the process were examined, and a possible mechanism is proposed.
TL;DR: A novel and facile route to functionalized mono/bicyclic 2,3-dihydro-4-pyridones has been developed via formal [5C + 1N] annulation of readily available alpha-alkenoyl ketene-(S,S)-acetals with various aliphatic primary amines.
TL;DR: Microwave-heated intramolecular in situ carbonylation of these electron-rich and sterically congested olefins conveniently afforded eight functionalized 3-acylaminoindanone derivatives in a novel synthetic process.
Abstract: The development of microwave-accelerated protocols for palladium(0)-catalyzed carbonylative cyclization of unsaturated aryl bromides and chlorides is described. By employing o-bromostyryl derivatives lacking substituents on the vinylic bond, molybdenum hexacarbonyl-mediated in situ carbonylation delivered a set of indan-1-one products in high yield after only 20 min of heating. Without the addition of the tri-tert-butylphosphine releasing Fu-salt ((t-Bu)3PHBF4), only incomplete conversions of sluggish o-styryl bromides and chlorides were realized. Internal and chemoselective palladium(0)-catalyzed Heck arylations of enamides afforded suitable starting materials for subsequent rapid ring-closing reactions. Microwave-heated intramolecular in situ carbonylation of these electron-rich and sterically congested olefins conveniently afforded eight functionalized 3-acylaminoindanone derivatives in a novel synthetic process. Attempted carbonylative annulation of electron-poor o-bromocinnamic acid derivatives furni...
TL;DR: The development of an approach leading to the total synthesis of dactylolide is described, which includes a catalytic asymmetric allylation, a diastereoselective pyran annulation, and a Horner-Wadsworth-Emmons macrocyclization.
TL;DR: Arynes generated in situ from 2-(trimethylsilyl)aryl triflates and CsF, undergo annulation by o-haloarenecarboxaldehydes in the presence of a Pd catalyst, providing a useful new method for the synthesis of fluoren-9-ones in good yields.
TL;DR: Using this method, plakinic acid analogues can be synthesized in three steps from the corresponding ketone and alkene, enabling the synthesis of a variety of functionalizable 1,2-dioxolanes.
TL;DR: In this paper, a mild and efficient route for the synthesis of quinolines and polycyclic quinoline using FeCl 3 or Mg(ClO 4 ) 2 as a novel catalyst via Friedlander annulation was described.
Abstract: A mild and efficient route for the synthesis of quinolines and polycyclic quinolines utilising FeCl 3 or Mg(ClO 4 ) 2 as a novel catalyst via Friedlander annulation was described.
TL;DR: A highly stereoselective total synthesis of (+)-asimicin is reported, which establishes all of the stereochemistry of the bis-tetrahydrofuran unit of the natural product.
Abstract: A highly stereoselective total synthesis of (+)-asimicin (1) is reported. The synthesis features two chelate-controlled [3 + 2] annulation reactionsone of which (e.g., 2 + 3) constitutes a key, convergent fragment assembly stepthat establish all of the stereochemistry of the bis-tetrahydrofuran unit of the natural product.
TL;DR: Benzo[b]furan-3-carboxylic acid was generated from 1 by forming three new bonds in one step via a Pd(II)-mediated cascade carboxylative annulation.
TL;DR: The silver(I)-catalyzed reaction of alkynones with alcohols represents a general tool for the synthesis of 1-allenyl isochromenes and most probably proceeds via the formation of benzopyrylium cation, which subsequently undergoes nucleophilic attack of an alcohol to give the annulation products.
Abstract: The silver(I)-catalyzed reaction of alkynones with alcohols represents a general tool for the synthesis of 1-allenyl isochromenes. The reaction most probably proceeds via the formation of benzopyrylium cation, which subsequently undergoes nucleophilic attack of an alcohol to give the annulation products.
TL;DR: Barbituric acid 1 and related beta-dicarbonyl compounds were dialkenylated under the phase-transfer catalyst conditions to generate the diallylated products and subjected to the ring-closing metathesis (RCM) reaction to deliver the corresponding spiro-annulated derivatives.
TL;DR: A rhodium-catalyzed annulation reaction of o-formylphenylboronic acid with alkynes occurred regioselectively at room temperature to give substituted 1H-inden-1-ol derivatives as mentioned in this paper.
Abstract: A rhodium-catalyzed annulation reaction of o-formylphenylboronic acid with alkynes occurred regioselectively at room temperature to give substituted 1H-inden-1-ol derivatives. o-Acetylphenylboronic...
TL;DR: The nucleophilicity of pyrrole has been exploited to rapidly assemble the bicyclic skeleton of indolizidine alkaloids as discussed by the authors, where the key sequence is the annulation of a second ring onto pyrdrug from a γ-lactone.
TL;DR: The 1,3-dipolar cycloaddition of an azomethine ylide, generated from isatin and benzylamine by a 1,5-prototopic shift route with various p -substituted 2,6-bis(arylmethylidene)cyclohexanones under different conditions, proceeded regioselectively to give novel dispiroheterocycles as discussed by the authors.
TL;DR: A new variant of the stereo-controlled [4+1] annulation strategy that provides especially efficient access to highly substituted and functionalized cyclopentenones is reported.
Abstract: Cyclopentenones serve as valuable synthetic building blocks and are themselves key features in the structure of a number of prostaglandins[1] and other bioactive natural products. Popular strategies for the construction of this important ring system include the intramolecular aldol reaction, the Nazarov cyclization,[2] the Rautenstrauch rearrangement,[3] and the Pauson–Khand reaction.[4,5] Only a few general [4+1] routes to five-membered carbocycles have been reported to date, one example being the method we developed based on anion-accelerated vinylcyclopropane rearrangements.[6,7] Recently, studies by us[8] and others[9] have led to several new [4+1] approaches to the synthesis of the 2-cyclopentenone ring system. Herein, we report a new variant of our stereo-controlled [4+1] annulation strategy that provides especially efficient access to highly substituted and functionalized cyclopentenones.
TL;DR: In this paper, a protocol for regioselective one-pot synthesis of 2-alkyl-3,4-dihydro-3-oxo-2 H -1,4benzoxazines under controlled microwave heating has been developed.
TL;DR: A route to 3,4-fused indoles via two consecutive palladium-catalyzed reactions; an intramolecular Heck reaction followed by a reductive N-heteroannulation is described, using a number of indoles prepared having a variety of ring sizes anchored to the 3- and 4-position of the indole nucleus.
TL;DR: A diastereoselective annulation of vinyl carbodiimides with chiral N-alkyl imines has been developed to access the stereochemically rich tricyclic core of the batzelladine alkaloids.
Abstract: A diastereoselective [4+2] annulation of vinyl carbodiimides with chiral N-alkyl imines has been developed to access the stereochemically rich tricyclic core of the batzelladine alkaloids. Its application to the asymmetric synthesis of batzelladine D permitted the use of long-range, directed hydrogenation and stereoselective intramolecular iodoamination as additional key steps to establish the remaining stereocenters within the natural product with excellent stereocontrol.