Showing papers on "Claisen rearrangement published in 1999"
TL;DR: C. Pericyclic Reactions 1210 1. [4+2]-Cycloadditions 1210 2. [3+2] CycloadDitions 1211 3. [2+2]."
Abstract: C. Pericyclic Reactions 1210 1. [4+2]-Cycloadditions 1210 2. [3+2]-Cycloadditions 1211 3. [2+2]-Cycloadditions 1212 D. Sigmatropic Rearrangements 1212 1. Claisen Rearrangement 1212 2. [2,3]-Wittig Rearrangements 1213 E. Radical Reactions 1214 IV. 1,3-Induction 1215 A. Chelation-Controlled 1,3-Induction 1215 B. Nonchelation-Controlled 1,3-Induction 1216 1. Cram−Reetz Model 1216 2. Evans Model 1216 C. 1,4-Induction 1219 V. Conclusion 1219 VI. References 1221
445 citations
TL;DR: In this review article, recent advances in the asymmetric Claisen rearrangement are described.
Abstract: Development of the asymmetric Claisen rearrangement is one of the challenging tasks in synthetic organic chemistry. There have been numerous reports of the asymmetric Claisen rearrangement based on the intramolecular chirality transfer using chiral substrates. On the other hand, reactions of achiral substrates with an external chiral activator have been studied during the last decade. In this review article, recent advances in the asymmetric Claisen rearrangement are described.
178 citations
TL;DR: In this paper, the aliphatic Claisen rearrangement of allyl vinyl ether and the aromatic Claisen reordering for allyl phenyl ether were investigated in a combined experimental and calculational study.
Abstract: The aliphatic Claisen rearrangement of allyl vinyl ether and the aromatic Claisen rearrangement of allyl phenyl ether are investigated in a combined experimental and calculational study. Theoretically predicted kinetic isotope effects (KIEs) at all levels disagree with about half of the literature experimental heavy-atom isotope effects. New experimental 13C and 2H isotope effects were determined by multisite NMR methodology at natural abundance, and 17O isotope effects were determined by novel NMR methodology. These new experimental isotope effects are inconsistent with the literature values and agree well the high-level predicted KIEs, suggesting that the prior theory/experiment disagreement results from inaccuracy in the experimental KIEs. A one-dimensional tunneling correction is found to improve kinetic isotope effect predictions in a number of reactions and is found to be sufficient to provide differences between predicted and experimental heavy-atom isotope effects on the order of the experimental ...
113 citations
TL;DR: In this paper, the authors describe a broadly useful Lewis acid-catalyzed [3, 3]-sigmatropic rearrangement that they expect will provide a new avenue for the development of an enantioselective catalytic Claisen process.
Abstract: Department of Chemistry, UniVersity of California, Berkeley, California 94720 ReceiVed June 14, 1999 Since its discovery in 1912,1 the Claisen rearrangement has become one of the most powerful tools for carbon-carbon bond formation in chemical synthesis.2 This [3,3]-sigmatropic rearrangement, which involves the conversion of an allyl vinyl ether to an R,â-disubstituted γ,δ-unsaturated carbonyl, generally proceeds with high levels of stereocontrol, securing its widespread use in natural product and medicinal agent synthesis.2 Activation of this rearrangement has traditionally been accomplished under thermal control; however, significant rate acceleration can be achieved through the incorporation of cationic3 or anionic4 charge in the bond reorganization event. Despite its prolific use in chemical synthesis and disposition toward charge acceleration, only two examples of catalytic Claisen variants have been reported.5 In this paper we describe a broadly useful Lewis acidcatalyzed [3,3]-sigmatropic rearrangement that we expect will provide a new avenue for the development of an enantioselective catalytic Claisen process.6 In 1978, Bellus and Malherbe reported the conceptually novel ketene-Claisen reaction.7 In an attempt to perform a [2 + 2] cycloaddition, the authors discovered that treatment of an allyl ether with dichloroketene resulted instead in the formation of a 1,3-dipolar allyl vinyl ether, which subsequently underwent [3,3]bond reorganization (eq 1). Although the scope of this reaction
79 citations
TL;DR: The mechanism of the enzyme and antibody-catalyzed Claisen rearrangement of chorismate to prephenate was investigated experimentally on model compounds and by using quantum chemistry calculations.
Abstract: The mechanism of the enzyme- and antibody-catalyzed Claisen rearrangement of chorismate to prephenate was investigated experimentally on model compounds and by using quantum chemistry calculations ...
72 citations
TL;DR: This palladium-catalyzed reaction proceeds under very mild conditions and is suitable for the synthesis of enantiomerically pure amino acids (see reaction scheme).
Abstract: Complementary to the Claisen rearrangement, the title reaction-which when carried out with chelated enolates of amino acid esters as nucleophiles gives rise to unsaturated amino acids-preferentially provides anti instead of syn products. This palladium-catalyzed reaction proceeds under very mild conditions and is suitable for the synthesis of enantiomerically pure amino acids (see reaction scheme). Tfa=trifluoroacetyl.
72 citations
61 citations
TL;DR: The polyene antibiotic myxalamide A has been prepared by total synthesis and illustrates a useful strategy for synthesis in which the high 1,2-stereocontrol achievable with the aldol reaction can be parlayed by other stereoselective processes so as to give compounds having two or more stereocenters with remote relationships.
Abstract: The polyene antibiotic myxalamide A (1) has been prepared by total synthesis. The synthesis illustrates a useful strategy for synthesis in which the high 1,2-stereocontrol achievable with the aldol reaction can be parlayed by other stereoselective processes so as to give compounds having two or more stereocenters with remote relationships. Application of the Evans asymmetric aldol reaction to aldehyde 13 gives the beta-hydroxy imide 17. Because the substrate is an alpha,beta-unsaturated aldehyde, the alcohol is allylic. After suitable functional group manipulation, this allylic alcohol is subjected to enolate Claisen rearrangement (as propionate 22) to give allylsulfide 23, having three stereocenters with a 1,4,5-relationship. Further functional group manipulation and one-carbon homologation converts this intermediate into 26, which is oxidized and subjected to Evans-Mislow allylsulfoxide rearrangement to obtain 27, having three stereocenters with a 1,2,5-relationship. The synthesis of myxalamide A was completed by converting aldehyde 30 into dienyne 40. Alkyne 40 was hydroborated with catechol borane, and the resulting E-vinylborane was subjected to Suzuki coupling with the Z-iodo triene 9 to provide myxalamide A (1).
58 citations
TL;DR: Allylic esters of peptides undergo Claisen rearrangement after deprotonation in the presence of tin chloride, giving rise to allylated peptides.
46 citations
46 citations
TL;DR: The ortho-metallated complex (R,R)-di-di-µ-chlorobis{9-[(1-dimethylamino)ethyl]-10-phenanthrenyl-C,N}dipalladium has been prepared and found to be a significantly better catalyst than its phenyl and naphthylamine analogues for the asymmetric Claisen rearrangement of a non-activated allyl imidate as discussed by the authors.
TL;DR: It is established that Claisen rearrangement is neither rhodium- nor acid-catalyzed but a reaction intrinsic to the intermediate enols that proceeds at a rate governed by enol substituents (R3, R4, R5).
TL;DR: In this paper, the chiral synthesis of the immunosuppressive sesquiterpene, FR65814 1 is described, and the cyclohexane ring in 1 was prepared in an optically active form from D-glucose using Ferrier's carbocyclization reaction.
TL;DR: In this paper, the chiral total synthesis of paniculide A (1 ), a highly oxygenated sesquiterpene possessing a bisabolane skeleton, starting from D-glucose is described.
TL;DR: In this paper, the C2-symmetric enediol easily derived from d -mannitol provided a chiral C8-building block, which was demonstrated to be versatile for divergent synthesis of both enantiomeric forms of substituted paraconic acids.
TL;DR: In this article, a polystyrene-diethylsilane resin (PS-DES) was treated with triflic acid to form a highly reactive polymer silyl triflate.
TL;DR: Chiral tridentate ligand ph-ambox ( 1 ) can form a cationic Pd(II) catalyst for the [3, 3]-sigmatropic rearrangement of allylic imidates to allylic amides with ees up to 83% for one substrate.
TL;DR: Asymmetric synthesis of 3′-C -methyl-4′-thio apion nucleosides was accomplished from the chiral intermediate as mentioned in this paper, which transferred chirality of quaternary carbon of the key intermediate via [3,3]-sigmatropic Claisen rearrangement with high enantiomeric excess.
TL;DR: Starting from achiral TFA-protected glycine crotyl ester (3), the interesting, suitable protected, enantiomerically pure β-hydroxy-γ-amino acid isostatine (7 ) was synthesized in only four steps as mentioned in this paper.
TL;DR: Racemic compounds of the antimalarial agents febrifugine and isofebrilugine were synthesized using an unusual Claisen rearrangement of allyl enol ether and stereoselective reduction of 2-allyl-3-piperidone.
Abstract: Racemic compounds (1 and 2) of the antimalarial agents febrifugine (d-1) and isofebrilugine (d-2) were synthesized using an unusual Claisen rearrangement of allyl enol ether (7) and the stereoselective reduction of 2-allyl-3-piperidone (8). This method is widely applicable to the synthesis of derivatives needed to study the structure-activity relationship of febrifugine.
TL;DR: The formal total synthesis of α-pinguisene and pinguisenol from liverworts is described in this article, which contains a cis-1,2,6,7-tetramethylbicyclo[4.3]nonane skeleton incorporating two vicinal quaternary carbon atoms and four cis oriented methyl groups.
Abstract: Formal total synthesis of (±)-α-pinguisene and (±)-α-pinguisenol, containing a cis-1,2,6,7-tetramethylbicyclo[4.3.0]nonane skeleton incorporating two vicinal quaternary carbon atoms and four cis oriented methyl groups on four contiguous carbon atoms, isolated from liverworts is described. Thus, an orthoester Claisen rearrangement of the allyl alcohol 14, obtained from the Hagemann’s ester 15, afforded the ene ester 18. Hydrolysis of the ketal and ester moieties transformed the ene ester 18 into keto acid 23. Intramolecular cyclopropanation of the diazo ketone 24 derived from the keto acid 23 afforded a 3∶2 mixture of chromatographically separable tricyclic diones 25 and 26. Simultaneous regioselective reductive cyclopropane-ring cleavage and reduction of the cyclohexanone carbonyl in the dione 25 with lithium in liquid ammonia furnished the keto alcohol 27, which on Wolff–Kishner reduction followed by oxidation of the alcohol afforded the bicyclic ketone 11, Schinzer’s precusor of pinguisenol 9 and α-pinguisene 10.
TL;DR: In this article, a total synthesis of racemic β-necrodol was described using an ortho-ester Claisen rearrangement as the key step to dictate a high level of trans-1,3-diastereoselection on a cyclopentane derivative.
TL;DR: The reaction of Garner aldehyde 1 with 2-bromo-3-3,3-trifluoropropene in the presence of Zn-Ag couple gave the fluorine-containing, optically active allylic alcohol 2 in 65% yield with a diastereomeric excess greater than 98% as mentioned in this paper.
Abstract: The reaction of Garner aldehyde 1 with 2-bromo-3,3,3-trifluoropropene in the presence of Zn–Ag couple gave the fluorine-containing, optically active allylic alcohol 2 in 65% yield with a diastereomeric excess greater than 98%. The treatment of Garner aldehyde 1 with CF3CFBr2 (3a) and CF3CCl3 (3b) in the presence of zinc powder and catalytic AlCl3 highly diastereoselectively afforded 4a and 4b, respectively, in moderate yield. The orthoester Claisen rearrangement of 4a, b and 2 provided a new way to highly functionalized amino alcohol derivatives 6a–f containing a limited number of fluorine atoms.
TL;DR: Cordiachromene was synthesized from 5-methyl hept-5-en-2-one by using a Claisen rearrangement as discussed by the authors, and it was shown that the rearrangements can be used to synthesize a variety of molecules.
TL;DR: A formal total synthesis of (±)-homogynolide-B, a sesquiterpene containing an α-spiro-β-methylene-γ-butyrolactone moiety spirofused to a bicyclo[4.3]nonane framework, is described in this article.
Abstract: A formal total synthesis of (±)-homogynolide-B, a sesquiterpene containing an α-spiro-β-methylene-γ-butyrolactone moiety spirofused to a bicyclo[4.3.0]nonane framework, is described. Thus, Hagemann’s ester 11 was converted into the allyl alcohol 16 in three steps. One-pot Claisen rearrangement of the allyl alcohol 16 and 2-methoxypropene in the presence of a catalytic amount of propionic acid afforded a 3∶2 epimeric mixture of the ketone 15 and further rearranged product 19. Ozonolysis followed by intramolecular aldol condensation and hydrogenation transformed the enones 15a,b into the key intermediate keto ketals 13a and 13b. Methoxymethylene Wittig reaction followed by bromoacetalisation converted the keto ketal 13a into the radical precursor bromo acetal 22a. The 5-exo-dig radical cyclisation of the bromo acetal 22a, followed by acid catalysed hydrolysis and oxidation, led to the keto spirolactone 12, Greene’s precursor of homogynolide-B. The same sequence transformed the keto ketal 13b into a 3∶2 mixture of the spirolactones 12 and 25, which on equilibration furnished the spirolactone 12. The stereostructure of the keto spirolactone 12 was unambiguously established by single-crystal X-ray diffraction analysis.
TL;DR: In this paper, the enantiomerically pure methyl substituted binaphthylamine 7 has been prepared via a regioselective directed ortho-metallation of the methoxy substituted Binaphthyl carboxylic acid 5 as the key step.