Showing papers on "Claisen rearrangement published in 1983"
TL;DR: The authors decrit les transpositions de Claisen d'un certain nombre de glycolates allyliques O-proteges and decrit le transposition de Clausen.
Abstract: On decrit les transpositions de Claisen d'un certain nombre de glycolates allyliques O-proteges
89 citations
TL;DR: La transposition de Claisen appliquee aux methoxycarbonylhydrazones preparees a partir des allyloxy cyclenones correspondantes conduit a des cyclanones dans un temps beaucoup plus court as discussed by the authors.
Abstract: La transposition de Claisen appliquee aux methoxycarbonylhydrazones preparees a partir des allyloxy cyclenones correspondantes conduit a des cyclanones dans un temps beaucoup plus court
60 citations
48 citations
TL;DR: The Claisen rearrangement of aryl propargyl ethers in poly(ethylene glycol) -200 at 200°C affords products in good yields.
38 citations
TL;DR: The enolate Claisen rearrangement of O-protected allylic glycolates yields functionalized acylic systems with high syn and anti stereoselectivity.
37 citations
TL;DR: In this article, the transposition allylique S→N d'allylthio-3 dihydro-2,5 triazine-1,2,4ones-5 en presence of palladium depend des substituants de la partie allyliques.
Abstract: La regioselectivite de la transposition allylique S→N d'allylthio-3 dihydro-2,5 triazine-1,2,4ones-5 en presence de palladium depend des substituants de la partie allylique. Les produits de transposition (allyl-4 et -2 tetrahydro-2,3,4,5 thioxo-3 triazine-1,2,4 ones-5) sont etudies en particulier par leur transformation en presence d'H 2 SO 4 dans l'acide formique en dihydro thiazolo [2,3-c]-triazine-1,2,4ones-4 et -thiazolo [3,2-b] triazine-1,2,4ones-7
36 citations
36 citations
TL;DR: The ester enolate Claisen rearrangement of (E)- and (Z)-2-butenyl 2-hydroxyacetates gave erythro- and threo-2-hydroxyl 3-methyl-4-pentenoic acids with high diastereoselectivity via silyl ketene acetals, respectively as discussed by the authors.
34 citations
30 citations
TL;DR: In this paper, the stereochimie de transposition des (butene-2yl [cis et trans] tosylmethyl-1 propenyl) ethers obtenus par addition catalytique de l'alcool crotylique cis and trans au tosyll-1 butadiene-1,2
Abstract: Etude de la stereochimie de la transposition des (butene-2yl [cis et trans] tosylmethyl-1 propenyl) ethers obtenus par addition catalytique de l'alcool crotylique cis et trans au tosyl-1 butadiene-1,2
30 citations
TL;DR: In this article, allylation (par des tosylates et halogenures d'alcene-2yle de dimethyl-and diisopropylamides et phenylamides des acides thiopropionique et benzenethioacetique) is defined.
Abstract: α-Allylation (par des tosylates et halogenures d'alcene-2yle de dimethyl- et diisopropylamides et phenylamides des acides thiopropionique et benzenethioacetique
TL;DR: Les sels de sodium ou de lithium d'alcools allyliques secondaires reagissent avec le N,N,N-trimethyl ammonioacrylate pour donner les acides alcene-2yloxy acryliques a partir desquels on obtient par chauffage des aldehydes homoallyliques.
Abstract: Les sels de sodium ou de lithium d'alcools allyliques secondaires reagissent avec le N,N,N-trimethyl ammonioacrylate pour donner les acides alcene-2yloxy acryliques a partir desquels on obtient par chauffage des aldehydes homoallyliques
TL;DR: In this article, the transposition de Claisen entre dialkylacetals d'alcanones-2 and alcools allyliques (hexene-2ol-1, hexene-1ol-3 and phenyl-3 propene 2ol-2) is described.
Abstract: Etude de la transposition de Claisen entre des dialkylacetals d'alcanones-2 et des alcools allyliques (hexene-2ol-1, hexene-1ol-3 et phenyl-3 propene-2ol-1). Preparation de cetones homoallyliques
TL;DR: In this paper, a (22E,24S)-ergosta-5,22-dien-3β-ol was developed from (20S)-6β-acetoxy-3α,5-cycle-5α-pregnane-20-carbaldehyde using the Claisen rearrangement of an appropriate precursor.
Abstract: A stereoselective synthesis of crinosterol, (22E,24S)-ergosta-5,22-dien-3β-ol, was developed from (20S)-6β-acetoxy-3α,5-cycle-5α-pregnane-20-carbaldehyde using the Claisen rearrangement of an appropriate precursor of established absolute configuration.
TL;DR: In this article, a survey of stereochemical control through sigmatropic rearrangements with emphases on their mechanistic grounds and their applicabilities (and potentials) as tools for acyclic stereocontrol is presented.
Abstract: This review represents a survey of stereochemical control through sigmatropic rearrangements with emphases on their mechanistic grounds and their applicabilities (and potentials) as tools for acyclic stereocontrol. The rearrangements concerned are thermally-allowed [3, 3]- and [2, 3]- sigmatropic rearrangements.The 1st chapter deals with an introductory aspect of the stereochemistries of the sigmatropic rearrangements in general and their synthetic potentials for achieving diastereoselective synthesis (internal asymmetric induction), chirality transfer (self-immolative asymmetric synthesis), and a combination thereof.The 2nd chapter is concerned with stereocontrol via [3, 3]-sigmatropic rearrangements, mainly the Claisen variants. First, the general stereochemistry of the Claisen rearrangement is discussed on mechanistic grounds. Second, a variety of highly diastereoselective Claisen modifications and their applications to natural product syntheses are described. Third, the synthetic potentialities of the 1, 3-transfer of chirality via the Claisen rearrangement are illustrated in the contexts of recent stereocontrolled syntheses of complex natural products. Fourth, the possibility of net remote asymmetric induction via the Claisen variant is discussed.The 3rd chapter deals mainly with stereocontrol via the [2, 3]-Wittig rearrangement with some emphasis on recent works in our laboratory. First, the transition-state models for the [2, 3]- Wittig variants are discussed in details. Second, a variety of highly diastereoselective [2, 3]-Wittig variants and their applications to natural product syntheses are described. both the 1, 3-and 1, 4-transfers of chirality via the [2, 3]-Wittig rearrangement are described. Fourth, the possibility of net 1, 5-asymmetric induction via the sequential [2, 3]-Wittig-Claisen and the [2, 3]- Wittig-[2, 3]-Wittig rearrangements are discussed.
TL;DR: In this article, the cyclohexene-3 carboxylate de methyle was used for the prephenate de disodium and son epimere of l'acide chorismique.
Abstract: Synthese totale de l'acide chorismique (±) en 11 etapes a partir du cyclohexene-3 carboxylate de methyle. Preparation du prephenate de disodium et de son epimere a partir du chorismate de dimethyle
TL;DR: Castasterone (22R,23R,24S)-2α,3α,22,23-tetrahydroxy-5α-ergostan-6-one (1) and its (22S,23S)-isomer have been synthesized from (20S)-6β-acetoxy-3β,5-cyclo-5β-pregnane-20-carbaldehyde.
Abstract: Castasterone (22R,23R,24S)-2α,3α,22,23-tetrahydroxy-5α-ergostan-6-one (1) and its (22S,23S)-isomer have been synthesized from (20S)-6β-acetoxy-3α,5-cyclo-5α-pregnane-20-carbaldehyde. The side chain with the correct stereochemistry was constructed via a Claisen rearrangement and the nuclear functionalities were introduced by osmilation of the intermediate obtained by opening of the cyclopropane ring with hydrochloric acid and dehydrohalogenation.
TL;DR: In this paper, a 5:1 preference for axial vs. equatorial allylation was shown in the Claisen rearrangement of the conformationally-rigid diosphenol allyl ether.
TL;DR: The linear furanocoumarin, hortiolone from Hortia arborea has been synthesised in five steps from 7-hydroxy-5-prenyloxycoumarins in 76% overall yield as mentioned in this paper.
TL;DR: Chiral induction (72-74% diastereomeric excess) is an auxiliary reagent mediated aza-Claisen rearrangement yielding 2- and 3-methylpent-4-enoic acids has been demonstrated as discussed by the authors.
TL;DR: In this paper, 2,3-Dihyroxypyridine has been dialkylated with allyl bromide and methallyl chloride to give 1,allyl-3-allyloxy-2-pyridone (2) and 1,methallyl -3-methal-loxy -2-polycyclic 2,pyridine (3), respectively.
TL;DR: In this paper, the acid-catalyzed ketal Claisen rearrangement was used to obtain mixtures of the isomeric γ, δ-unsaturated ketones, with the more highly substituted isomer predominating by a factor of 2-4:1.
TL;DR: The first total and stereoselective synthesis of (±)-tecomanine (1), one of the monoterpene alkaloids, was accomplished starting from ethyl 1, 6-dihydro-3 (2H)-oxopyridine-1-carboxylate (2a).
Abstract: The first total and stereoselective synthesis of (±)-tecomanine (1), one of the monoterpene alkaloids, was accomplished starting from ethyl 1, 6-dihydro-3 (2H)-oxopyridine-1-carboxylate (2a). The allylic alcohol (8), obtained as a major product on treatment of 2a with methylmagnesium iodide, was subjected to the Claisen rearrangement using ethyl (1-propenyl) ether to afford the aldehyde (30) which was converted to the methyl ketone (32). The acetal (33) was stereoselectively hydrated by a hydroboration-oxidation process to give the alcohol (34) in an excellent yield. To prevent formation of the furan (38), the product (34) was initially hydrolyzed and then oxidized to afford the diketone (36). Although 36 is a mixture of two diastereoisomers due to the configuration of the side-chain methyl group, each isomer, 36a and 36b, provided solely the desired product (40) upon base-catalyzed intramolecular aldol reaction. The urethane (40) was easily converted into (±)-tecomanine (1) by LiAIH4 reduction and subsequent PCC oxidation.
TL;DR: Obliquetol 5 has been synthesised for the first time using improved conditions for prenyloxy-coumarin Claisen rearrangements as mentioned in this paper, and the structure assigned to the natural coumarin, celerin, requires revision.
TL;DR: In this article, the results from the acid catalysed Claisen rearrangement of the methyl esters (1c-g) indicate that regiochemical control is independent of internal hydrogen bonding.
Abstract: The observed products from the acid catalysed Claisen rearrangement of the methyl esters (1c–g) indicate that, unlike the thermal reaction, regiochemical control is independent of internal hydrogen bonding.
TL;DR: The Claisen rearrangement of some allyl naphthalen-1-yl ethers has been examined, together with methods for modification of the resulting 2-ally 1 side chain this article.
Abstract: The Claisen rearrangement of some allyl naphthalen-1-yl ethers has been examined, together with methods for modification of the resulting 2-ally1 side chain. Isomerization of the C-allyl substituent to a prop-1-enyl group followed by ozonolysis gives a formyl derivative, while ozonolysis of a 2-(2-methylprop-2-enyl) moiety or mercuriation of a 2-(2-chloroprop-2-enyl) substituent leads to an acetonyl derivative. Treatment of phenols with iodine(I) acetate and an excess of silver(I) acetate gives 4-hydroxyaryl acetates, probably via dienone intermediates.
TL;DR: Gorgosterol (1), a C30 marine sterol containing cyclopropane in the side chain has been stereoselectively synthesized utilizing orthoester Claisen rearrangement and intramolecular alkylative cyclopanation as mentioned in this paper.
Abstract: Gorgosterol (1), a C30 marine sterol containing cyclopropane in the side chain has been stereoselectively synthesized utilizing orthoester Claisen rearrangement and intramolecular alkylative cyclopropanation.
TL;DR: Synthese de cyclohepta [b] thiophenes a partir d'allylthio-2-and de propargylthio -2 tropones.
Abstract: Synthese de cyclohepta [b] thiophenes a partir d'allylthio-2- et de propargylthio-2 tropones
TL;DR: In this paper, it was found that the Claisen rearrangement of the lithium enolate of 1-(2-thienyl)alkyl alkanoate in refluxing THF resulted in the formation of 2-(3-thiamyl)-alkanoic acid (2).
Abstract: It was found that the Claisen rearrangement of the lithium enolate of 1-(2-thienyl)alkyl alkanoate in refluxing THF resulted in the formation of 2-(3-thienyl)alkanoic acid (2). Similarly, when the lithium enolate of 4-(2-thienyl)-4-butanolide was stirred at room temperature in the presence of hexamethylphosphoric triamide, 5,6-dihydro-4H-cyclopenta[b]thiophene-4-carboxylic acid was obtained. Further, it was found that the Birch reduction of 2 and subsequent alkylation with benzyl bromide gave a regioselective ring-opening product, 4-benzylthio-3-ethyl-3-alkenoic acid, in a good yield. The Birch reduction of 2-thienylacetic acid, followed by alkylation with benzyl bromide, also gave (Z)-3-benzylthio-3-hexenoic acid as the main product.