Showing papers on "Annulation published in 1980"
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TL;DR: In this paper, a two-step sequence converts cyclic enones to fused methylenecyclopentanes using the annulation reagent 2-chloromethyl-3-trimethylsilylpropene.
37 citations
37 citations
TL;DR: In this paper, aldol condensation promoted by L-amino acids produced the optically active (+)-4-(3-butenyl)-7a-methyl-5,6,7, 7a-tetrahydroindane-1,5-dione in high chemical and optical yields.
33 citations
TL;DR: In this article, a tris-annulation reagent was used to synthesize 7-acetoxy-1,11-dodecadien-3-one, which was converted to 9decen-5-olide after hydrolysis and decarboxylation.
26 citations
TL;DR: The stereoselective hydroboration and carbonylation of highly functionalized 1,4-dienes affords trans-hydrindanones in good yield.
25 citations
TL;DR: In this paper, the annulation of isoquinoline derivatives to form the 8-oxoprotoberberine derivatives is described and the key step of the reaction involves intramolecular alkylation of the Reissert compounds.
TL;DR: Sulphuric acid catalyzed ring closure of propargyl alcohol dianion adduct of 2-cyclododecenone gives bicyclo[10.3.0]pentadec-1(12),2-dien-13-one as discussed by the authors.
TL;DR: In this paper, the synthesis of tricyclo [3.3.0.02,8] octan-3-one has been carried out in order to explore its potential utility as a versatile synthon for polycyclopentanoid terpenes and prostacyclin analogs.
Abstract: Chemical transformation of tricyclo [3.3.0.02,8]octan-3-one (1) have been carried out in order to explore its potential utility as a versatile synthon for polycyclopentanoid terpenes and prostacyclin analogs. Various functionalizations of rings A and B and annulation of a third ring C were achieved in generally high yields. The system provides for a large measure of regio- and stereoselective reaction control.
TL;DR: In this article, the palladium-catalyzed cyclization of 2-substituted 3-oxo-8-phenoxy-6-octenoates is used to construct CD rings of steroids.
TL;DR: A total synthesis of β-cuparenone, which highlights the advantages and disadvantages of the three-carbon annulation process, is described in this article, where the authors highlight the advantages of the annulation method.
TL;DR: In this paper, an unusual phosphine sulfide to phosphine oxide exchange reaction was found during the annulation of (3,5-dimethylphenyl)-(2-hydroxy-2-methylpropyl)methylphosphine sulfides (3) using the mild cyclodehydration reagent methanesulfonic acid/phosphorus pentoxide.
TL;DR: In this paper, the reductive annulation with LiAlH4 was used for the synthesis of 5, 9- and 8, 13-diazasteroids (15, 16, 17, 18, and 19) and the stereochemistry of 15 and 19 was discussed.
Abstract: Syntheses of 5, 9- and 8, 13-diazasteroids (15) and (19) employing reductive annulation with LiAlH4 are described. The stereochemistry of 15 and 19 is discussed.
TL;DR: In this paper, it was shown that the reaction of methyl valelolactim and methyl caprolactim with cyclic β-aminoesters, such as 2-carbethoxymethyl piperidine derivatives (4 or 5), often gave two kinds of products apparently arising from the imine and enamine forms.
Abstract: Annulation reactions of methyl valelolactim (2) and methyl caprolactim (3) with cyclic β-aminoesters, such as 2-carbethoxymethyl piperidine derivatives (4 or 5), often gave two kinds of products apparently arising from the imine and enamine forms of 2 and 3 These chemical properties were consistent with NMR observations of lactim ethers in CD3OD solution
TL;DR: In this paper, the penam backbone was completed through the formation of the 1,5-bond in a reductive annulation of chlorosulphenyt chlorides with tin(II) chloride.
Abstract: Diphenylmethyl and benzyl esters of (±)-6-azido-3-carboxypenam-2-spirocyctopentanes (18) and (20)–(23) have been obtained in a multi-step synthesis from 2-amino-2-(1-mercaptocyclopentyl)acetic acid (1). The penam backbone was completed through the formation of the 1,5-bond in a reductive annulation of chlorosulphenyt chlorides (14)–(17) with tin(II) chloride. The parent non-fused β-lactams (8)–(11) were prepared from diphenylmethyl or benzyl [1-(p-methoxybenzylthio)cyclopentyl]-2-[(methylthio)methylimino]acetate, (6) or (7), azidoacetyl chloride, and triethylamine. When (6) was used in this reaction, the 2-methylthio-3-azidoacetylthiazolidine-5-spirocyclopentanecarboxylic ester (12) and diphenylmethyl 2-azidoacetylamino-2-[(1-p-methoxybenzylthio)cyclopentyl]acetate (13) were isolated as by-products.
TL;DR: In this article, the annelation of α-pyridones to five membered ring systems is demonstrated by the synthesis of a series of 2-azafluorenones.
TL;DR: In this article, the reaction of lactim thioethers with 1-carbethoxymethyl-1, 2, 3, 4-tetrahydroisoquinoline (4) was investigated.
Abstract: In order to examine the difference in chemical properties between lactim thioethers and lactim ethers, the reaction of lactim thioethers with 1-carbethoxymethyl-1, 2, 3, 4-tetrahydroisoquinoline (4) was investigated.
TL;DR: In this article, a new annelation method involving cationic olefin cyclization via neighboring sulfur participation was demonstrated on a thiasteroid synthesis, which proceeds in an entirely stereospecific manner.
TL;DR: In this article, a dianion generated from 2,4-dimethyl-3-furoic acid with 3methoxy-2-methyl-2 -cyclohexen-1-one gave 4-methyl 2-(3-oxo-2)-methyl-1 -cycloehexenylmethyl)-3 furoic acids, which was converted in five steps into (±)-furanoeremophilane-3,6-dione.
Abstract: Treatment of a dianion generated from 2,4-dimethyl-3-furoic acid with 3-methoxy-2-methyl-2-cyclohexen-1-one gave 4-methyl-2-(3-oxo-2-methyl-1-cyclohexenylmethyl)-3-furoic acid. Catalytic hydrogenation of the alkylated product followed by dehydrative annelation yielded 14-norfuranoeremophilane-4,6-dione, which was converted in five steps into (±)-furanoeremophilane-3,6-dione. (±)-Ligularone has been derived from the 3,6-dione.
TL;DR: In this paper, the effect of benzene annelation on the physical properties (UV, PMR, CMR, electron affinity) of o-tropoquinone was evaluated.
Abstract: The title compound, a benzolog of o-tropoquinone, was synthesized by the DDQ oxidation of the corresponding hydroxytropolone. Effect of benzene annelation on the physical properties (UV, PMR, CMR, electron affinity) of o-tropoquinone was evaluated. The annelation causes more modification to o-tropoquinone than to o-benzoquinone. This may be due to the reduced planarity of 7-membered quinone ring in the title compound. Easy reduction by HCl and facile BF3-induced aromatization to 1,2-dihydroxynaphthalene were observed.