Showing papers on "Annulation published in 1982"
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TL;DR: In this paper, the β-iodo enones were treated with lithium (phenylthio)(cyclopropyl)cuprate and obtained high yields of the annulation products of the sesquiterpenoid (±)-zizaene.
Abstract: Treatment of the β-iodo enones 7–10 with lithium (phenylthio)(cyclopropyl)cuprate provided excellent yields of the corresponding β-cyclopropyl α,β-unsaturated ketones 11–14, respectively. When 3-isopropenyl-2-cyclohexen-1-one (16) was allowed to react with dimethyloxosulfonium methylide in dimethyl sulfoxide – tetrahydrofuran, 3-(1-methylcyclopropyl)-2-cyclohexen-1-one (17) was produced in 59% yield. Although thermal rearrangement (~425–450 °C) of compounds 11 and 17 produced high yields of the annulation products 19 and 22, respectively, similar reactions involving the β-cyclopropyl enones 12 and 13 were not efficient in terms of production of the corresponding bicyclic systems (23, 26, and/or 27, respectively). In these cases, predominant (24 + 25 from 12) or significant (28 + 29 from 13) amounts of monocyclic dienones were formed. The annulation product 22 served as a convenient starting material for a new formal total synthesis of the sesquiterpenoid (±)-zizaene (30). Conjugate addition of lithium div...
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TL;DR: The title compound 1 was synthesized by the reaction of dipotassium bicyclo(6.0)undeca-2,4,6-triene-1,8-diide, 3, and UCl/sub 4/, and its crystal and molecular structure was determined by single-crystal x-ray diffraction.
24 citations
TL;DR: In this article, the synthesis of dibenzofurans from diphenyl ethers by non-phenolic oxidative coupling, u.v. irradiation, and by reaction with palladium(II) acetate has been investigated.
Abstract: The synthesis of dibenzofurans from diphenyl ethers by non-phenolic oxidative coupling, u.v. irradiation, and by reaction with palladium(II) acetate has been investigated. 9-Isopropyl-6-methyl-3-pentyldibenzofuran-1-ol (cannabifuran)(35), a minor cannabis constituent, has been synthesized by annulation of 4-isopropyl-7-methylbenzofuran-2-carbaldehyde (28) by Wittig reaction with 2-carboxy-1-ethoxycarbonylethyltriphenylphosphorane and ring closure and functional-group modification of the resultant (E)-4-(4-isopropyl-7-methylbenzofuran-2-yl)-3-methoxycarbonylbut-3-enoic acid (29).
TL;DR: In this paper, a five-ring annulation sequence for 1-trimethylsilylcyclopropylethylenes was proposed, based on pyrolysis of silyl substituted cyclopentenes in high yield.
TL;DR: In this paper, a convergent synthesis of 2-cyclopenten-1 -ones is reported, where the triethyl orthoformate is replaced with ferric chloride hexahydrate.
Abstract: A new, convergent synthesis of 2-cyclopenten-1 -ones is reported. Treatment of dimethyl 2-oxopropylphosphonate (21) with excess triethyl orthoformate in the presence of ferric chloride hexahydrate ...
TL;DR: In this article, a simple process for aryl annulation based on the inverse electron demand Diels-Alder reaction of 5,6-substituted-3-carbomethoxy-2-pyrones with 1,1-dimethoxyethylene is described.
TL;DR: In this paper, metal hydride reduction of acetate groups adjacent on rings to exocyclic α,β-unsaturated nitriles generates alkoxyhydrides which perform stereospecific intramolecular hydrides transfers to the β-position of the conjugated system; hydrolysis of the γ-hydroxynitriles so formed gives, after lactonization, trans-fused γ -butyrolactones whose relative stereochemistry is derived from the configuration of the original acetate.
TL;DR: In this article, the preparation of substituted phenols from cycloalkanones by elaboration of an aromatic ring is described, and the preconditioning of the ring is discussed.
TL;DR: In this paper, products from stereospecific vinylcuprate addition to hydroazulenic γ-trimethylsiloxy-α, β-unsaturated cycloheptenones are converted directly to trans-fused γlactones by 1) BH3-THF, 2) B-H hydrolysis, and 3) PCC oxidation.
TL;DR: The reaction of 3-methyl-1,2-alkadienephosphonic acid (i.e. 3-alkyl-3-methylsubstituted allenephosphoric) dimethyl esters with methylsulfenyl chloride 2 is oriented mainly to the 1-2-oxaphosphol-3ene ring products 3a-d (as diastereoisomeric mixtures when alkyl ≠ CH3) as mentioned in this paper.
Abstract: The reaction of 3-methyl-1,2-alkadienephosphonic acid (i.e.3-alkyl-3-methylsubstituted allenephosphonic) dimethyl esters 1 with methylsulfenyl chloride 2 is oriented mainly to the 1,2-oxaphosphol-3-ene ring products 3a-d (as diastereoisomeric mixtures when alkyl ≠ CH3). In low extent common 1,2-adducts 4a-d as E,Z-mixtures are also formed. The ratio 3:4 and, in particular the E:Z ratio rises by increase of the size of the alkyl group at the allenic C3-atom of 1. Lowering the temperature of the reaction of 1 and 2 leads to an increase of the annulation stereoselectivity although it remains not very high in the studied temperature interval (−45° – +15°C).
TL;DR: In this paper, a photochemical annulation of isoquinoline derivatives to form the 8-oxoprotoberberine derivatives is described, and the key step of the reaction is an intramolecular photochemical arylation of 3-chloro-2-phenethyl-1-isoquinolone.
Abstract: The novel photochemical annulation of isoquinoline derivatives to form the 8-oxoprotoberberine derivatives is described. The key step of the reaction is an intramolecular photochemical arylation of 3-chloro-2-phenethyl-1-isoquinolone. The same arylation also proceeds intermolecularly, when 3-chloro-1-isoquinolones are irradiated in benzene.
TL;DR: In this paper, the authors summarized the syntheses of various tetracyclic and pentacy-clic condensed thiophene systems and discussed the physicochemical analogies between the benzene and thiophenes rings.
Abstract: Publisher Summary This chapter summarizes the syntheses of various tetracyclic and pentacyclic condensed thiophene systems. The close physicochemical analogies between the benzene and thiophene rings are discussed. There are many advantages of using the thienolog correlation. Perhaps the most important advantage is that one can use the structural formulas of the known and predicted polycyclic aromatic hydrocarbons as a point of reference for writing the structures of all of the numerous condensed thiophenes that are theoretically possible. Most commonly, tetracyclic and pentacyclic condensed thiophenes are synthesized by the process of annulation, i.e., by constructing one or more rings onto a precursor molecule by an intermolecular or intramolecular process. Thus, most of the synthetic methodologies are categorized first in terms of the nature of the ring produced, whether a sulfur heterocyclic ring or a carbocyclic one, and second in terms of the reagents or the type of reaction used. A few synthetic methods that do not fit neatly into one of the annulations categories are also discussed in the chapter.
TL;DR: In this paper, the double Michael reaction of 3-methyl-, 2-3-dimethyl-, and 3-5dimethyl-4-methylenecyclohex-2-enone with dimethyl 3-oxoglutarate in dimethyl sulphoxide in the presence of potassium fluoride gave stereoselectively 9-methyl, 1,9-dimethylamine, and 4-9dimethyl, 6,8-dimethoxycarbonyl-cis-decahydronaphthalene-2,7-dione,
Abstract: Double Michael reaction of 3-methyl-, 2,3-dimethyl-, and 3,5-dimethyl-4-methylenecyclohex-2-enone with dimethyl 3-oxoglutarate in dimethyl sulphoxide in the presence of potassium fluoride gave stereoselectively 9-methyl-, 1,9-dimethyl-, and 4,9-dimethyl-6,8-dimethoxycarbonyl-cis-decahydronaphthalene-2,7-dione, respectively, and starting from these annulation products some sesquiterpenes having the cis-decahydronaphthalene skeleton were formally synthesised.
TL;DR: In this article, a convergent synthesis of 2-cyclopenten-1 -ones is reported, where the triethyl orthoformate is replaced with ferric chloride hexahydrate.
Abstract: A new, convergent synthesis of 2-cyclopenten-1 -ones is reported. Treatment of dimethyl 2-oxopropylphosphonate (21) with excess triethyl orthoformate in the presence of ferric chloride hexahydrate ...
TL;DR: In this article, a photochemical annulation of isoquinoline derivatives to form the 8-oxoprotoberberine derivatives is described, and the key step of the reaction is an intramolecular photochemical arylation of 3-chloro-2-phenethyl-1-isoquinolone.
Abstract: The novel photochemical annulation of isoquinoline derivatives to form the 8-oxoprotoberberine derivatives is described. The key step of the reaction is an intramolecular photochemical arylation of 3-chloro-2-phenethyl-1-isoquinolone. The same arylation also proceeds intermolecularly, when 3-chloro-1-isoquinolones are irradiated in benzene.