Showing papers on "Annulation published in 1990"
TL;DR: In this article, a general strategy for the synthesis of highly substituted polycyclic aromatic and heteroaromatic compounds was developed, which is achieved simply by the irradiation of a dichloroethane solution of an acetylene derivative and a vinyl or aryl α-diazo ketone.
Abstract: A general strategy for the synthesis of highly substituted polycyclic aromatic and heteroaromatic compounds has been developed. The new aromatic annulation is achieved simply by the irradiation of a dichloroethane solution of an acetylene derivative and a vinyl or aryl α-diazo ketone. Mechanistically, the reaction proceeds via the photochemical Wolff rearrangement of the diazo ketone to generate an aryl- or vinylketene, followed by a cascade of three pericyclic reactions. A variety of substituted phenols, naphthalenes, benzofurans, benzothiophenes, indoles, and carbazoles can be prepared by using the method
166 citations
TL;DR: Both enantiomers of the pyrrolizidine alkaloid trihydroxyheliotridane 1 have been prepared in an efficient and stereocontrolled fashion in 10 steps as discussed by the authors.
Abstract: Both enantiomers of the pyrrolizidine alkaloid trihydroxyheliotridane 1 have been prepared in an efficient and stereocontrolled fashion in 10 steps. Key steps involve the microbial oxidation of chlorobenzene with Pseudomonas putida to afford chiral cyclohexadienediol4 with high enantiomeric excess and its conversion to lactone 7, from which either enantiomer of azide 18 can be prepared. The azides are converted to the title compounds via a [4 + 11 pyrroline annulation based on an intramolecular azidediene cycloaddition/thermal rearrangement.
139 citations
96 citations
88 citations
TL;DR: In this article, a new fulvene synthesis results from the palladium-catalyzed [2 + 2+2] annulation of 1 mol of a β-substituted vinyl iodide and 2mol of a monosubstitized acetylene.
Abstract: A new fulvene synthesis results from the palladium-catalyzed [2+2+2] annulation of 1 mol of a β-substituted vinyl iodide and 2 mol of a monosubstituted acetylene. This variant of the Heck reaction tolerates a wide range of substrate substituents with the best results obtained by using the catalyst, Pd(CH 3 CN) 2 Cl 2 . Addition of Cu I I to the reaction affords high yields of 1,3-enyne and no fulvene. A [6.5]spiro system is formed from 4-tert-butyl-1-cyclohexenyl triflate and a biphenyl is formed from 1-aryl-1-bromoethene under these conditions. A mechanism for this novel fulvene synthesis is proposed
80 citations
73 citations
TL;DR: The authors derives cyclohexahydro, perhydro indenone-4 and perhydroid cyclopenta [c] pentalenone, a partir de la reaction de cyano trimethylgermyl-3 butene-3yl cuivre-lithium avec un derive de cyclochexene-2one ou un derive of bicyclo [3.3.0] octene-1one-3, via la cyclisation de derives iodo-3' butene,3'yl-3 cyclo
Abstract: Synthese de derives d'hexahydro ou perhydro indenone-4 et de perhydro cyclopenta [c] pentalenone-4 a partir de la reaction de cyano trimethylgermyl-3 butene-3yl cuivre-lithium avec un derive de cyclohexene-2one ou un derive de bicyclo [3.3.0] octene-1one-3, via la cyclisation de derives iodo-3' butene-3'yl-3 cyclohexanone ou d'iodo-3' butene-3'yl-7a perhydro indenone-2 respectivement
68 citations
TL;DR: In this paper, a new three-step procedure for pyridine annulation is described and illustrated with efficient syntheses of various 1,6- 1,7-, and 1,8-naphthyridin-2-ones as well as 6-chloroquinolin-1-one.
Abstract: A new three-step procedure for pyridine annulation is described and illustrated with efficient syntheses of various 1,6- 1,7-, and 1,8-naphthyridin-2-ones as well as 6-chloroquinolin-2-one. The regiospecific ortho metalation and subsequent formylation of 2-, 3-, or 4-(pivaloylamino)pyridines provides the corresponding protected ortho aminopyridinecarboxaldehydes as key intermediates in this procedure. After condensation of these aldehydes with tert-butyl lithioacetate the resulting β-hydroxy esters are treated with refluxing aqueous HCl to generate the naphthyridine system in excellent yield. Naphthyridines with diverse substitution patterns in either of the pyridine rings are available by appropriate modification of the overall pyridine annulation sequence
63 citations
TL;DR: In this article, the annulation with 1,3-diiodopropane to give (-)-(SS)-1,2,3,5,6,7,7-hexahydro-8-[(4-methylphenyl)sulfinyl]indolizine (6), which was converted into (-)-elaeokanine B (three steps) and (+)-ELaeOKanine A (four steps)
Abstract: α-Lithiated (+)-(R)-4,5-dihydro-2-[[(4-methylphenyl)sulfinyl]methyl]-3H-pyrrole (4) underwent annulation with 1,3-diiodopropane to give (-)-(SS)-1,2,3,5,6,7-hexahydro-8-[(4-methylphenyl)sulfinyl]indolizine (6), which was converted into (-)-elaeokanine B (three steps) and (+)-elaeokanine A (four steps)
46 citations
TL;DR: Synthese de triacetoxy-5,11,12 tetramethyl -5,12a, 13,13,13 perhydro methanobenzocyclodecenone-8 a partir d'un derive d'iminomethano-8a,4a biphenylene.
Abstract: Synthese de triacetoxy-5,11,12 tetramethyl-5,12a,13,13 perhydro methanobenzocyclodecenone-8 a partir d'un derive d'iminomethano-8a,4a biphenylene
46 citations
TL;DR: In this paper, the reaction of 2,3-bis(phenylsulfonyl)-1, 3-butadiene with various amines was reported as a method for synthesizing these heterocycles in excellent yield.
Abstract: In this paper we report on the reaction of 2,3-bis(phenylsulfonyl)-1,3-butadiene with various amines as a method for synthesizing these heterocycles in excellent yield
TL;DR: In this article, an efficient Robinson annulation was established through the Michael addition of enol silyl ethers to α-enones catalyzed by dibutyltinbis(triflate) followed by the MeONa-mediated intramolecular aldol condensation of the adducts.
TL;DR: The stereochemistry of the free-radical chain mediated methylenecyclopentane annulation of olefins with 1 can be influenced significantly by the choice of catalyst radical as discussed by the authors.
TL;DR: Azomethine ylides, prepared from imidazolinium salts, undergo 1,3-dipolar cycloaddition with a variety of dipolarophiles to produce hexahydropyrrolo[1,2- a ]imidazoles, which are reduced to pyrrolidines; with 2-chloroacrylonitrile as dipolarophile, pyrroles can be prepared from the cycloadducts by elimination as discussed by the authors.
TL;DR: A series of α-trimethylsilyl-substituted phenyl sulfones bearing an ω-p-toluenethiosulfonyl αsubstituent were synthesized and subjected to treatment with tetra-n-butylammonium fluoride to provide the corresponding monocyclic sulfides (6-, 7-, and 8-membered rings) as discussed by the authors.
Abstract: A series of α-trimethylsilyl-substituted phenyl sulfones bearing an ω-p-toluenethiosulfonyl α-substituent were synthesized and subjected to treatment with tetra-n-butylammonium fluoride to provide the corresponding monocyclic sulfides (6-, 7-, and 8-membered rings). This intramolecular sulfenylation reaction was also used in an annulation sequence. The cyclic sulfides obtained were oxidized to the bis (sulfone) derivatives and subjected to Ramberg-Backlund ring contraction to give the monocyclic olefins and an exocyclic fused olefin
TL;DR: In this article, the lithium dienolate of 4-siloxy-2-bromocrotonate was condensed with several enones to afford silyl enol ether terminated vinylcyclopropanes, which were rearranged at low temperatures under various conditions to the corresponding oxycyclopentenes.
Abstract: The lithium dienolate of 4-siloxy-2-bromocrotonate was condensed with several enones to afford silyl enol ether terminated vinylcyclopropanes, which were rearranged at low temperatures under various conditions to the corresponding oxycyclopentenes. An application of this methodology to the synthesis of highly functionalized oxygenated cyclopentanoids such as the iridoids is suggested
TL;DR: In this article, a tricyclic product, 7,7dimefhyltricyclo[6.2.1] was obtained from norcamphor.
Abstract: 4,4-Dimethyl-2-oxabicyclo[3.2.1]octan-3-one (10), obtained in two steps from norcamphor, was converted to 3-(1,1-dimethyl-2-oxopropyl)cyclopentanone (14), then selectively ketalized. The ketal function underwent Lewis acid catalysed spiro-annulation with 1,2-bis)trimethylsiloxy)cyclobutene (4) yielding 7-(1,1-dimethyl-2-oxopropyl)spiro[4.4]nonane-1,4-dione (21), and intramolecular titanium-induced ketone–ketone coupling and oxidation afforded (±)-isokhusimone (3) in an overall yield of 35% from norcamphor. In an alternative approach, the ethylene ketal of methyl 2-mefhyl-2-(3-oxocyclopentyl)propanoate (27) was prepared from 10. Spiro-annulation proceeded in good yield, but subsequent titanium-induced ketone–ester coupling failed to provide the desired tricyclic product, 7,7-dimefhyltricyclo[6.2.1.01,5]undecane-2,6-dione (30). Keywords: annulation, carbonyl coupling, isokhusimone, terpene.
TL;DR: Propargylic carbonates react with 2,3-diacylsuccinates in the presence of Pd(0) and phosphine ligands to give 3-methylene dihydropyran derivatives in moderate to good yields.
TL;DR: Esters et al. as discussed by the authors proposed a new approach to condensation of pyrimidine annulations via Iminophosphoranes via isocyanates and showed that it is possible to obtain a stabilized carbodiimide to which alcohols or amines add before condensation occurs to 4(3H)-quinazolinones.
TL;DR: The newly prepared 1-bromo-2-methylene-3-phenylsulfonylpropane 2 reacts with α,β unsaturated esters in a Michael induced ring closure to provide cyclopentane derivatives with complete diastereoselectivity as discussed by the authors.
TL;DR: In this paper, a reaction intramoleculaire de Mukaiyama de dimethylacetal de dioxo-3,7.4 via une reaction intrameroleculaitre de this paper.
Abstract: Synthese de methoxy-2 tricyclo [5.4.2.0 4,12 ] tridecanedione-10,13 a partir du triquinane octahydro cyclopenta [a] pentalenedione-3,4 via une reaction intramoleculaire de Mukaiyama de dimethylacetal de dioxo-3,7. bicyclo[6.3.0] undecaneacetaldehyde-9
TL;DR: In this article, the double bond migration into the thermodynamically more stable internal conjugated position completes the annulation scheme with (Z)-1,2-bis(phenylsulfonyl)ethylene.
Abstract: 1-(1-Ethoxyvinyl)cycloalkenes, readily available by palladium-catalyzed condensation of enol triflates with ethyl vinyl ether or its α-trimethylstannyl derivative, enter into Diels-Alder reaction with (Z)-1,2-bis(phenylsulfonyl)ethylene. These adducts undergo smooth reductive desulfonylation to provide cyclohexenones after enol ether hydrolysis. Migration of the double bond into the thermodynamically more stable internal conjugated position completes the annulation scheme
TL;DR: The title carbocations have been produced by the reaction of silver trifluoromethanesulfonate with mixed orthothioesters as discussed by the authors, and they have been shown to provide an efficient, chemoselective route for appending six-membered rings to nonactivated aromatic systems.
TL;DR: New double annulation reactions of 1,5-diynes with activated alkenes are catalysed by cobalt(0) complexes, and can also occur in the absence of cobalt to give new classes of compounds, containing exocyclic double bonds, if terminal methyl groups are present on the triple bonds.
Abstract: New double annulation reactions of 1,5-diynes with activated alkenes are catalysed by cobalt(0) complexes, and can also occur in the absence of cobalt to give new classes of compounds, containing exocyclic double bonds, if terminal methyl groups are present on the triple bonds.
TL;DR: One-carbon-atom Michael donors are used to initiate convergent and flexible [1+2+3]-hexannulations and [1 +2+2]-pentannulations in which the initial nucleophilic carbon atom terminates the reaction sequence in an ionic or carbon-centered radical fashion as discussed by the authors.
Abstract: One-carbon-atom Michael donors are used to initiate convergent and flexible [1+2+3]-hexannulations and [1+2+2]-pentannulations in which the initial nucleophilic carbon atom terminates the reaction sequence in an ionic fashion as an electrophilic center or in a carbon-centered radical fashion as a nucleophilic center. This protocol is used to prepare regiospecifically substituted bicyclic ketones and lactones and a cis-bicyclic tetrahydrofuran
TL;DR: In this article, the methyl enol ether of 2-methylcyclohexanone reacts regiospecifically with the optically active forms of but-3-yn-2-ol and but-1,2-dienyl 2-enol.
Abstract: The methyl enol ether of 2-methylcyclohexanone reacts regiospecifically with the optically active forms of but-3-yn-2-ol and but-3-en-2-ol. (R)-But-3-yn-2-ol yields an approximately 4 : 1 mixture of (R)-2-methyl-2-(R-buta-1,2-dienyl)cyclohexanone and the corresponding SR compound. By contrast the but-3-en-2-ol reaction is ca. 96% enantioselective; (R)-but-3-en-2-ol gives (R)-2-(trans-but-2-enyl)-2-methylcyclohexanone and (S)-but-3-en-2-ol gives the corresponding (S)-cyclohexanone. These Claisen rearrangement products have been transformed into Robinson-type annulated ketones. Cleavage of some highly hindered esters has been carried out efficiently by sodium methylsulphinyl-methanide in dimethyl sulphoxide.
TL;DR: In this paper, a formal synthesis of (2R-cis)-4-methyl-1-(2,3,4,5-tetrahydro-5-methyl-[2, 3′-bifuran]-2-pentanone, or ipomeamarone (1) [494-23-5] was accomplished from 3-furaldehyde 5 and ethyl-2-bromocrotonate 4.