Showing papers on "Claisen rearrangement published in 1978"
TL;DR: In this article, an unprecedented [3, 3]-sigmatropic rearrangement via a 1, 3-dipolar intermediate takes place, leading to O-, S- or Se-esters of α,α-dichloro-γ, δ-unsaturated acids containing an inverted allylic group.
Abstract: During the reaction of allyl ethers, allyl sulfides and allyl selenides with in situ prepared dichloroketene (1), 2 competing pathways are observed. Besides [2+2]-cycloaddition, an unprecedented [3,3]-sigmatropic (Claisen) rearrangement via a 1,3-dipolar intermediate takes place. It leads to O-, S- or Se-esters of α,α-dichloro-γ, δ-unsaturated acids containing an inverted allylic group. Starting from cyclic n-membered α-vinyl-substituted ethers, lactones with n+4-membered rings are formed. A very facile synthesis of the naturally occurring macrolides (±)-phoracantholide I (10) and (±)-phoracantholide J (11) illustrates the synthetic utility of this new ‘ketene’ Claisen rearrangement.
59 citations
TL;DR: In this article, the naturally occurring 10-membered lactone phoracantholide J (8a) has been synthesized as its racemate in a sequence of six steps.
Abstract: Starting from 5-chloro-2-pentanone (1) the naturally occurring 10-membered lactone phoracantholide J (8a) has been synthesized as its racemate in a sequence of six steps (Scheme 2). Salient features of the syntheis include an internal selenium assisted acetal formation (45) and a stereoselective Claisen rearrangement (678). This general synthetic strategy offers an alternative approach towards the construction of macrocyclic lactones.
50 citations
27 citations
TL;DR: In this article, a new version of the ester Claisen rearrangement was proposed, where the addition of benzeneselenenenyl bromide to ethyl vinyl ether followed by alcoholysis of the initially formed β-bromoalkyl selenide by primary, secondary or tertiary allylic alcohols gave the mixed acetals 3a-e.
Abstract: Regiospecific addition of benzeneselenenyl bromide to ethyl vinyl ether followed by alcoholysis of the initially formed β-bromoalkyl selenide 1 by primary, secondary or tertiary allylic alcohols 2a-e gave the mixed acetals 3a-e. Subsequent oxidation and thermal treatment of the corresponding selenoxides 4a-e furnished after saponification the γ, δ-unsaturated acids 7a-e in excellent overall yields. The entire sequence (Scheme 2) represents a new version of the ester Claisen rearrangement.
17 citations
TL;DR: Claisen Rearrangement of 2-Propinyl (3-Pyridyl) and Allyl (3pyridine) Ethers as mentioned in this paper showed that in both DMF and decane at 208° in a sealed tube, furopyridines and pyranopyridine were formed.
Abstract: Claisen Rearrangement of 2-Propinyl (3-Pyridyl) and Allyl (3-Pyridyl) Ethers1
2-Propinyl (3-pyridyl) ether (1), synthesized from the corresponding 3-pyridinol, was heated in DMF or decane at 208° in a sealed tube. In this way the furopyridines 2 and 3 were formed, and furthermore the pyranopyridine 4 if decane was used as solvent (Scheme 1). The same reactions took place with (2-methyl-3-pyridyl) 2-propinyl ether (14). In DMF only 15, and in decane 16 as well as 15 were formed (Scheme 3). The rearrangement of the pyridine derivative 17, which is substituted in both O-positions to the ether moiety, gave in both DMF and decane the diastereoisomeric tetracyclic compounds 18 and 19. The same kind of reaction took place with 25 (Scheme 4).
In the thermolysis of the allyl 3-pyridyl ether (27) cyclization was observed, too. The isolated product has the structure of the dihydrofuropyridine 28 (Scheme 6). The substituted allyl 3-pyridyl ether 30 reacted in the same way to the dihydrofuropyridine 31 (Scheme 6).
16 citations
TL;DR: In this article, primary and secondary allyl alcohols add to allenyl phenyl sulphoxides to form enol ethers that undergo Claisen rearrangement and elimination of benzenesulphenic acid, producing 2,4-dienones.
Abstract: Primary and secondary allyl alcohols add to allenyl phenyl sulphoxides to form enol ethers that undergo Claisen rearrangement and elimination of benzenesulphenic acid, producing 2,4-dienones.
12 citations
11 citations
TL;DR: The thio-Claisen rearrangement has been carried out on 2-allylthiopyrrole, l-methyl-2-ally lthiopryrrole and 2,5-dially lthypyrrole.
Abstract: The thio-Claisen rearrangement has been carried out on 2-allylthiopyrrole, l-methyl-2-allylthiopyrrole, and 2,5-diallylthiopyrrole. The products were trapped by acetylation of the β-allyl-α-thiols....
10 citations
TL;DR: In this article, a new type of amino-Claisen rearrangement was proposed, aromatic ammonium NCL rearrangements, which enables the introduction of functional group into the ortho position of aniline derivatives.
Abstract: Investigation of pyrolytic reactions of N-allylanilinium salts led to the finding of a new type of amino-Claisen rearrangement, aromatic ammonium N-Claisen rearrangement. This reaction enables the introduction of functional group into the ortho position of aniline derivatives. Products are potential precursors for indoline and indole preparations.
9 citations
TL;DR: In this paper, NMR analyses were performed on reaction products obtained from the flash vacuum pyrolysis (FVP) of phenyl..gamma..-deuteropropargyl ether(I) and 2 deuterophenyl propargyl e ether(II) to ascertain the reaction mechanism.
Abstract: NMR analyses were performed on the reaction products obtained from the flash vacuum pyrolysis(FVP) of phenyl ..gamma..-deuteropropargyl ether(I) and 2-deuterophenyl propargyl ether(II) to ascertain the reaction mechanism. The FVP was carried out at 460/sup 0/C and 0.02 Torr. The NMR spectrum of undeuterated 2-indanone in carbon tetrachloride displayed peaks at delta 7.15 (singlet, aromatic hydrogen's) and 3.25 (singlet, nonaromatic hydrogen's) and with an integration constant of 1.00 : 1.00, while the NMR spectrum of the deuterated 2-indanone derived from I produced an aromatic protons/nonaromatic protons ratio of 1.30 : 1.00. The NMR analyses of the reaction products from FVP of II indicate that at the rate-determining transition state the oxygen-propargylic (..cap alpha.. carbon) bond is stretched in advance of any significant bond formation between the acetylenic carbon (..gamma.. carbon), the Claisen type rearrangement was classified as a nonsynchronous process and the proposed mechanism agrees with previous studies.
8 citations
TL;DR: In this article, the authors describe experiments on the synthesis of the title compound, which is of interest as a ring A intermediate for a synthesis of vitamins D. The primary α-phenylthioacetate of (±)-4-hydroxycyclohex-1-enemethanol was protected and subjected to Claisen rearrangement to give mixed α-PHI-γδ-unsaturated acids which were converted into iodo-lactones and, after oxidation, into sulphoxides, which were thermolysed to provide δ-
Abstract: The paper describes experiments on the synthesis of the title compound, which is of interest as a ring A intermediate for a synthesis of the vitamins D. The primary α-phenylthioacetate of (±)-4-hydroxycyclohex-1-enemethanol was protected and subjected to Claisen rearrangement to give mixed α-phenylthio-γδ-unsaturated acids which were converted into iodo-lactones and, after oxidation, into sulphoxides, which were thermolysed to provide δ-iodo-αβ-unsaturated γ-lactones; these were then converted into the racemic form rac-(27) of the title compound.In a second (perferred) route, (+)-cyclohex-4-ene-1, trans-2-dimethanol (29) was first converted by standard methods into (1S,5R)-6-methylene-2-oxabicyclo[3.3.1]nonan-3-one (36) and then into the diol (43), from which the synthesis of the optically active compound (27) was completed by a sulphoxide thermolysis.
TL;DR: In this paper, the total synthesis of rac-kaur-16-ene-11α, 15α-diol via a sequence of reactions including the Birch reduction of alcohol 4 and the Claisen rearrangement of vinyl ether 34 is described.
Abstract: Total synthesis of rac-kaur-16-ene-11α, 15α-diol (1) via a sequence of reactions including the Birch reduction of alcohol 4 and the Claisen rearrangement of vinyl ether 34 as the key steps is described.
TL;DR: In this article, the authors proposed a thermally-clasisen rearrangement of 1,2-diallyloxyanthraquinone to give 2-allyl-1-hydroxyanthrquinone.
Abstract: Thermal Claisen rearrangement of 1,2-diallyloxyanthraquinone gives, among other products, 2-allyl-1-hydroxyanthraquinone.
TL;DR: In this article, primary and secondary allyl alcohols add to allenyl phenyl sulphoxides to form enol ethers that undergo Claisen rearrangement and elimination of benzenesulphenic acid, producing 2,4-dienones.
Abstract: Primary and secondary allyl alcohols add to allenyl phenyl sulphoxides to form enol ethers that undergo Claisen rearrangement and elimination of benzenesulphenic acid, producing 2,4-dienones.
TL;DR: In this paper, the 2,4-dienals were obtained by adding sodium derivatives of allyl alcohols to phenylthioacetylene and forming adducts which on oxidation and pyrolysis undergo Claisen rearrangement and elimination of benzenesulphenic acid.
Abstract: Addition of sodium derivatives of allyl alcohols (2) to phenylthioacetylene (1) forms adducts (3) which on oxidation and pyrolysis undergo Claisen rearrangement and elimination of benzenesulphenic acid to yield the 2,4-dienals (6).
TL;DR: In this paper, a new type of amino-Claisen rearrangement was proposed, aromatic ammonium NCL rearrangements, which enables the introduction of functional group into the ortho position of aniline derivatives.
Abstract: Investigation of pyrolytic reactions of N-allylanilinium salts led to the finding of a new type of amino-Claisen rearrangement, aromatic ammonium N-Claisen rearrangement. This reaction enables the introduction of functional group into the ortho position of aniline derivatives. Products are potential precursors for indoline and indole preparations.
TL;DR: The thio-Claisen rearrangement has been carried out on 2-allylthiopyrrole, l-methyl-2-ally lthiopryrrole and 2,5-dially lthypyrrole as discussed by the authors.
Abstract: The thio-Claisen rearrangement has been carried out on 2-allylthiopyrrole, l-methyl-2-allylthiopyrrole, and 2,5-diallylthiopyrrole. The products were trapped by acetylation of the β-allyl-α-thiols....
TL;DR: In this paper, Mesyl and Tosylaniline reagieren thermisch in N,N-Dibutylanilin in Gegenwart kleiner Mengen Triphenylphosphin nach Claisen zu den Verbindungen.
Abstract: Die Mesyl- und Tosylaniline (I) reagieren thermisch in N,N-Dibutylanilin in Gegenwart kleiner Mengen Triphenylphosphin nach Claisen zu den Verbindungen (II).
TL;DR: In this article, the enolate Claisen rearrangement of the α-methoxyacetate of the allylic alcohol was used to obtain the β,γ-unsaturated ester.
Abstract: The ester enolate Claisen rearrangement of the α-methoxyacetate of the allylic alcohol (2) followed by oxidative decarboxylation of the dianion derived from the resulting α-methoxycarboxylate provides an efficient preparation of the β,γ-unsaturated ester (5), and hence leads to (6), the functionality of which is common to many mono- and sesqui-tetrpenes.
DOI•
01 Oct 1978TL;DR: In this article, the Claisen rearrangement of 7-cinnamyloxy derivatives of 3-methoxyflavone (2), 4-methylcoumarin (7) and isoflavone (13) yielded 8-(1-phenyl-2-propenyl)-7-hydroxy-3-mETHoxyflavinone (3), 4methyl-8-(1phenyl)-1-pro-penyl), 7-hydroxyl-4-methyl-7-cylindrical-cyclohexane (7
Abstract: The Claisen rearrangement of 7-cinnamyloxy derivatives of 3-methoxyflavone (2), 4-methylcoumarin (7) and isoflavone (13) yield 8-(1-phenyl-2-propenyl)-7-hydroxy-3-methoxyflavone (3), 4-methyl-8-(1-phenyl-1-propenyl)-7-hydroxycoumarin (9) and 8-(1-phenyl-1-propenyl)-7-hydroxyisoflavone (14) respectively. The compound 3 represents the normal rearranged product and further has structural features similar to those present in some natural neoflavonoids; whereas other products (9 and 14) are abnormal ones formed by further allylic rearrangement of the normal ones (say 8).
TL;DR: In this paper, various reactions of interest in medicinal chemistry, such as aromatic substitution, halogenation, oxidation, by the use of oxidants absorbed on alumina or silica, reactions regarding carboxylic acids and derivatives, and various miscellaneous reactions have been noted.
Abstract: Publisher Summary This chapter discusses the various reactions of interest in medicinal chemistry, such as aromatic substitution, halogenation, oxidation, by the use of oxidants absorbed on alumina or silica, reactions regarding carboxylic acids and derivatives, and various miscellaneous reactions. Several improvements in the aldol reaction have been noted. Coupling of an α-bromocarbonyl compound with another carbonyl compound via dialkylaluminum chloride–zinc, produces aldol regiospecifically in high yield. Fluoride ion catalyzed reaction of enol sily ethers and carbonyl compounds prepares aldol products regiospecifically. Aldol type products are stereoselectively synthesized by Claisen rearrangement of silylketene acetals. For aromatic substitution, arylamines are directly converted to aromatic hydrocarbons by alkyl nitrites in DMF. Alternatively, an aryl halide is produced when cupric halides are added in acetonitrile. The alkyl-nitrite deamination method also provides a convenient variant of the meerwein arylation reaction. In a related method, diazonium ions are converted to phenols with cuprous oxide-cupric nitrate. This radical process avoids the problems of the strongly acidic classical transformation. Phenols may also be converted to anilines via smiles rearrangement that is greatly accelerated by HMPA solvent. An interesting anionic equivalent of the Friedel–Crafts cycloacylation is demonstrated in this chapter. The oxidative reagents absorbed on alumina or silica are generally milder and more selective, and provide for convenient reaction workup. Oxidations of cyclobutanol to cyclobutanone, and β-hydroxysulfides and selenides to the β-keto compounds are accomplished by trichloroacetaldehyde on alumina.
01 Jan 1978
TL;DR: Diphenylseleninic anhydride, PhSE(= 0)0.Sec(=0)Ph, has proved has proved to be the new reagent for the application of selective ortho-substitution of phenols by attachment of the substituting reagent to the phenolic hydroxy group and subsequent rearrangement of this derivative by a cyclic mechanism into the orthoposition.
Abstract: Selective ortho-substitution of phenols can be secured, in principle, by attachment of the substituting reagent to the phenolic hydroxy group and subsequent rearrangement of this derivative by a cyclic mechanism into the orthoposition. So far, only one example of this principle (the Claisen rearrangement) is well established. For ortho-hydroxylation, a phenolic ester of selenium(IV) should have the desired properties. Diphenylseleninic anhydride, PhSE(=0)0.Sec(=0)Ph, has proved has proved to be the new reagent for the application of this mechanism. Several phenols, including models of the phenolic ring A of tetracycline, gave o-hydroxydienones, with quinones and phenylselenated species as by-products, when treated with diphenylseleninic anhydride. When the phenols were converted into their corresponding anions before treatment with the anhydridide, the o-hydroxydienones were obtained in good yield free from other products arising from reaction at the para position. When phenols were added to a warm solution of diphenylseleninic anhydride, they were oxidized to the o-quinones even when the phenols were not substituted in para position.