Showing papers on "Annulation published in 1985"
TL;DR: In this paper, the synthesis of anthracyclinones via tandem cycloaddition/annulation reactions with Fischer carbene complexes has been examined and the potential of these reactions for coupling to organochromium compounds has been demonstrated.
102 citations
TL;DR: Cyclisation [3+2] d'allenylsilanes avec des aldehydes (obtention de dihydro-2,3 furannes) ou des equivalents de N-acylimines (ethoxy-6 piperidone, ethoxy-5 pyrrolidone-2) derives d'ethoxy3 phtalimide, N-t-butoxymethylbutyramide) (Obtention of lactames derives d"indolizines, pyrro [1,
Abstract: Cyclisation [3+2] d'allenylsilanes avec des aldehydes (obtention de dihydro-2,3 furannes) ou des equivalents de N-acylimines (ethoxy-6 piperidone-2, ethoxy-5 pyrrolidone-2, derives d'ethoxy-3 phtalimide, N-t-butoxymethylbutyramide) (Obtention de lactames derives d'indolizines, pyrrolizines et pyrrolo [1,2-a] isoindoles et de propionyl-1 pyrrolines-2)
85 citations
58 citations
TL;DR: The reaction of α,β-unsaturated acyl-silanes with allenylsilanes can be directed to produce either five or six-membered carbocyclic compounds as discussed by the authors.
56 citations
TL;DR: On prepare plusieurs systemes contenant deux olefines electrophiles, lune etant une cetone α-methylene, l'autre un ester α,β-insature as discussed by the authors.
Abstract: On prepare plusieurs systemes contenant deux olefines electrophiles, l'une etant une cetone α-methylene, l'autre un ester α,β-insature. L'addition de Michael de l'enolate de lithium du trimethylsiloxy-2methyl-3butene-1 sur ces systemes, suivie d'une addition intramoleculaire de Michael, conduit a la formation du systeme tricyclique a 3 noyaux en C 6 . On a pu ainsi obtenir le dimethyl-3aflavinine
54 citations
TL;DR: In this article, a concise synthesis for the neurotoxic physostigmine alkaloid d,l-eserethole is described which reliess upon an intramolecular cycloaddition reaction involving a non-stabilized imidate methylide and an unactivated alkene.
49 citations
46 citations
TL;DR: In this paper, an intramolecular lactone annulation of activated carboxylic acids onto olefins by manganese(III) acetate yields bicyclo[3.3.0] and [4.O]lactones.
45 citations
TL;DR: In this article, an easily effected aromatic annelation involving reaction of O-thioalkyl and O -thioaryl substituted Phenyl radicals with alkynes to give 2-substituted benzo[b]thiophenes is described.
Abstract: An easily effected aromatic annelation is described involving reaction of O-thioalkyl and O-thioaryl substituted Phenyl radicals with alkynes to give 2-substituted benzo[b]thiophenes; the mechanism is discussed.
42 citations
TL;DR: Dienic azide 7 was found to yield dehydropyrrolizidines 10 and 11 on thermolysis and the synthesis of these compounds is described and the mechanistic implications as well as synthetic utility of this new annulation sequence is discussed as mentioned in this paper.
39 citations
TL;DR: In this article, a ring tansfer reaction of furans to fused furans by tandem intramolecular Diels-Alder reaction and base-catalyzed ring-opening of the adducts has been developed.
TL;DR: Synthese de systemes bicyclo [3.3.0 2,5 ] undecanes a partir de triethylsilylethers de cyclopentanone as discussed by the authors.
Abstract: Synthese de systemes bicyclo [3.3.0] octanes et tricyclo [6.3.0.0 2,5 ] undecanes a partir de triethylsilylethers de cyclopentanone
TL;DR: In this paper, the preparation of the chiral butenolide (4b) was described, together with its use in annulation reactions yielding stereochemically defined bicyclo[4.3.0], [3.1.3], and [4.0] ring systems; the synthetic utility of these species was indicated.
Abstract: The preparation of the chiral butenolide (4b) is described, together with its use in annulation reactions yielding stereochemically defined bicyclo[4.3.0], [3.3.0], and [3.1.0] ring systems; the synthetic utility of these species is indicated.
TL;DR: Alkylation of cyclic ketones and α-methoxycarbonyl ketones with 4-iodo-2-trimethylstannylbut-1-ene, and subsequent (Ph3P)4Pd-catalysed cyclization of the enol trifluoromethanesulphonates derived form the alkylation products, from the basis of new annulation sequences which result in the formation of diene systems.
Abstract: Alkylation of cyclic ketones and α-methoxycarbonyl ketones with 4-iodo-2-trimethylstannylbut-1-ene and/or 5-iodo-2-trimethylstannylpent-1-ene, and subsequent (Ph3P)4Pd-catalysed cyclization of the enol trifluoromethanesulphonates derived form the alkylation products, from the basis of new annulation sequences which result in the formation of diene systems.
TL;DR: In this article, the sequential treatment of α,β-unsaturated ketones with (phenylseleno)alanes or titanates followed by representative β,γ-unaturated aldehydes has been shown to furnish β-(phenylselseno)ketols in high yield.
TL;DR: In this paper, a Lewis acid-catalysed intramolecular directed aldol condensation of enol silanes and acetals was used to prepare tetrahydropyran-4-ones, oxepan- 4-ones and oxocan-5-ones.
Abstract: A Lewis acid-catalysed intramolecular directed aldol condensation of enol silanes and acetals was used to prepare tetrahydropyran-4-ones, oxepan-4-ones, and oxocan-4-ones. The course of the cyclisations was influenced by the Lewis acid and the stereochemistry of the starting material.
TL;DR: In this paper, a process of conjugate addition and 5-exo-digonal closure was used to produce five-membered carbocycles from β-Acetylenic radicals.
Abstract: β-Acetylenic radicals, e.g., (6b) and (12), generated in three steps from epoxides or in two steps from α-halogenoketones, respectively, react with electron-deficient olefins to produce five-membered carbocycles by a process of conjugate addition and 5-exo-digonal closure.
TL;DR: Synthese de naphtoquinones-1,2 a partir de naphtols-2 et d'(hydroxy-2 isoprenyl-3)-, (hydroxy)-2 methyl-3]- et (hydroxymethyl-2 methoxy-5 methyl-4 naphtocinones-2,4.
Abstract: Synthese de naphtoquinones-1,2 a partir de naphtols-2 et d'(hydroxy-2 isoprenyl-3)-, (hydroxy-2 methyl-3)- et (hydroxy-2 methoxy-5 methyl-3) naphtoquinones-1,4
TL;DR: Etude des cycloadditions de thiazolo [3,2c] quinazolinioolates-3 and thiazolinediones-1,6 as mentioned in this paper.
Abstract: Etude des cycloadditions de thiazolo [3,2-c] quinazolinioolates-3 et de thiazolo [3,2-a] quinazolinioolates-1 avec des dipolarophiles ethyleniques ou acetyleniques: obtention de pyrido [1,2-c] quinazolinones-8 et de pyrido [1,2-a] quinazolinediones-1,6
TL;DR: In this paper, the annulation of a carbocyclic five-membered ring to an aryl group is achieved in a template synthesis based on addition of two equivalents of methyl isocyanide to the corresponding aar carbene complex (CO)5M = C(Oalkyl)aryl (M = Cr, Mo) (1).
Abstract: Die regiospezifische Anellierung eines carbocyclischen Funfrings an einen Arylrest gelingt in einer Templatsynthese durch Addition zweier Aquivalente Methylisocyanid an den entsprechenden Arylcarbenkomplex (CO)5M = C(OAlkyl)Aryl (M = Cr, Mo) (1). Der Funfring besteht aus dem Carben-, den beiden Isocyanid- sowie dem α- und dem ipso-Kohlenstoff des Arylrests. Die Additionsprodukte lassen sich als tiefblaue (CO)4M-1,2-Bis(imino)cyclo-pentan-Komplexe 2 isolieren. Neben 2 entstehen Saureamide 4. Durch oxidative Zersetzung von 2 mit HIO4werden – vermutlich uber Radikalkationen – 1,2-Cyclopentandione 6 sowie Carbonsauren 7 und 8 erhalten.
Organic Syntheses with Transition Metal Complexes, 11. Cyclopentane Annulation of Aromatic Compounds. Regiospecific Template Synthesis via Arylcarbene Complexes and Methyl Isocyanide
The regiospecific annulation of a carbocyclic five-membered ring to an aryl group is achieved in a template synthesis on addition of two equivalents of methyl isocyanide to the corresponding arylcarbene complex (CO)5M = C(Oalkyl)aryl (M = Cr, Mo) (1). The five-membered ring contains the carbene-, the two isocyanide- as well as the α- and the ipso-carbon atom of the aryl group. The products are easily isolated as deeply bluecolored (CO)4M-1,2-bis(imino)cyclopentane complexes 2. Oxidative decomposition of 2 by HIO4 yields 1,2-cyclopentanediones 6 and carboxylic acids 7 and 8 via an intermediate radical cation. Side products of the synthesis of 2 are the amides 4.
TL;DR: In this article, a new method for annulation of rings onto existing allylic alcohol derivatives is presented, which involves Claisen rearrangement followed by nitrile oxide-olefin cycloaddition.
TL;DR: In this article, a short synthesis of the 10-methyl-4-keto-hydroazulenes using organo-iron reagents is described, and the synthesis is shown to yield 10 methyl-4.
TL;DR: In this article, the reaction of ketene-S, N-acetals (1-6), which are useful synthetic intermediates for heterocycles, with aryl isocyanates (7) is described.
Abstract: Reaction of ketene-S, N-acetals (1-6), which are useful synthetic intermediates for heterocycles, with aryl isocyanates (7) is described. Annulation of 1-3 and 4-6 with 7 in boiling toluene gave bicyclic (8-10) and monocyclic (11-13) uracil derivatives, respectively. Addition of 2, 3, and 4 to 7 under mild conditions afforded the 1 : 1 adducts (18, 19, and 21), respectively. Compounds 18 and 19 also reacted with 7 to give bicyclic uracil derivatives.
TL;DR: In this paper, the effect of chain substitution, Lewis acid, and acetal structure on the efficiency of the 8-exoeendon cyclisations was examined, and the beneficial effect of gem-dimethyl substitution was discussed.
Abstract: β-Alkoxycyclo-octanones were formed in poor to moderate yield by a Lewis acid-catalysed intramolecular directed aldol reaction between an acetal and an enol silane. From 10 examples, the effect of chain substitution, Lewis acid, and acetal structure on the efficiency of the 8-exoeendon cyclisations was examined. The beneficial effect of gem-dimethyl substitution is discussed.