Stereo- and regiochemistry of the Claisen rearrangement: applications to natural products synthesis

Ziegler, Frederick E.

doi:10.1021/ar50114a006

Cited by 260 publications

(67 citation statements)

References 26 publications

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“…Depending on the parent substances utilised, there exist a number of modifications, which have found a vast number of applications in laboratory-scale syntheses [8]. The most important ones are depicted in Scheme 3: Scheme 3.…”

Section: Methodsmentioning

confidence: 99%

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Claisen, Cope and Related Rearrangements in the Synthesis of Flavour and Fragrance Compounds

Nowicki

2000

Molecules

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Section: Methodsmentioning

confidence: 99%

“…Sigmatropic rearrangements are more and more frequently employed in organic syntheses, including the synthesis of natural products (eg.-terpenoids) [8], flavours and fragrances [9][10][11][12].…”

Section: Methodsmentioning

confidence: 99%

Claisen, Cope and Related Rearrangements in the Synthesis of Flavour and Fragrance Compounds

Nowicki

2000

Molecules

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“…The species (6) and (7) are reactive intermediates; this fact and the high reaction temperature (130 "C) would offer a reasonable explanation of the diminished selectivity.…”

Section: 2-disubstituted Double Bondsmentioning

confidence: 98%

Stereochemistry of [2,3]Sigmatropic Rearrangements

Hoffmann

1979

Angew. Chem. Int. Ed. Engl.

206

190

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Stereoselective synthesis is attracting more and more attention. Successful stereoselective syntheses require the availability of reactions of known stereochemistry which give maximum yields of the desired products. This is particularly so with reactions proceeding via cyclic transition states. Of these, the stereochemistry of [3,3]sigmatropic processes has long been known. This article now summarizes the factors determining the stereoselectivity of [2,3]sigmatropic rearrangements.Volume 18 . Number 8 August 1979Pages 563 -640 I . Introduction [3,3]Sigmatropic rearrangements (a) (Scheme 1; Claisen, Cope, oxy-Cope, hetero-Cope rearrangement)" 41 have been thoroughly studied with regard to their stereochemical course[5 and belong to the standard repertoire of stereoselective syntheses of ~lefins[~-'l or centers of chirality[* ''I. Recent outstanding applications can be seen in a juvenile hormone synthesis ['21, transformation of sugars into prostagland i n~ [ '~' , or the synthesis of tocopherol['4'. I IAmong the [2,3]sigmatropic rearrangements there is a great variety of reactions of types I and I1 [Scheme 1, eq. (b) and (c)]''~ 2'1 which frequently occur at lower temperatures than the [3,3]sigmatropic rearrangements. The five-membered cyclic transition state of [2,3]sigmatropic rearrangements shows greater conformational "flexibility" than the six-membered transition state of [3,3]sigmatropic rearrangements and should therefore be far more susceptible to the effects of stereochemical control by substituents122'. In view of this synthetic potential it was most appropriate that studies on [2,3]sigmatropic rearrangements should have been accompanied by a thorough examination of their stereochemistry which began almost simultaneo~sly[~~l. It is thus all the more surprising that the starting materials for the preparative investigation of [2,3]sigmatropic rearrangements were (purposely?) chosen in such a way that no stereochemical problems occurred. However, this meant forgoing stereochemical information.The following compilation of results should provide an insight into the stereochemistry of [2,3]sigmatropic rearrangements.Scheme I . Survey of 13.31-and [2,3jsigmatropic rearrangements. The suggested valences may be bonds to other atoms or lone pairs. Formal charges follow from the nature and the bonding situation of atoms X, Y, Z. Stereochemkal Observables['I Prof. Dr The rearrangements (b) and (c) lead to formation of a new double bond between C-1 and C-2. Given two different substituents on C-I this double bond may result in an E or 2 configuration. Hence the factors determining the configuration of the new double bond are of interest. 563The centers X and C-I of the reactants of rearrangements (b) and (c) are chiral if they each bear two different substituents. A lone pair will also be regarded as a substituent in these considerations. C-3 [rearrangements (b) [rearrangements (b)] are prochiral if the substituents on these centers are different. In the course of rearrangement, the chirality of X and c -I di...

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“…± After many unsuccessful attempts to assemble the crucial isoxazolidine 28, the route shown in Scheme 2 finally led to the desired target. The Claisen-rearrangement modification of the original Johnson procedure [12] by Saucy et al [13], applied to but-3-en-2-ol (18) and triethyl orthoacrylate (19) [14] [15]. Treatment of 20 with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in boiling benzene for 2 days furnished Michael acceptor 21, to which the lithium enolate of methyl cyanoacetate was added to give 22 in excellent yield as a 5 : 4 mixture of two diastereoisomers.…”

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confidence: 99%

Towards a New Synthetic Entry into theIboga-Alkaloid Family

Frauenfelder

Borschberg

2000

HCA

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Dedicated to Professor Albert Eschenmoser on the occasion of his 75th birthday A novel retrosynthetic concept is presented that, in principle, allows access to many hitherto not accessible representatives of the Iboga-alkaloid family. The flexibility required by this approach is provided through a highly convergent assembly of the target, which allows for a control over the substitution pattern of the indole sub-system, as well as over the relative configuration of the aliphatic core of these alkaloids. The key step for the construction of the latter consists in an intramolecular nitrone-olefin 1,3-dipolar cycloaddition reaction of 26 to yield the crucial tricyclic isoxazolidine derivative 28.

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Stereo- and regiochemistry of the Claisen rearrangement: applications to natural products synthesis

Cited by 260 publications

References 26 publications

Claisen, Cope and Related Rearrangements in the Synthesis of Flavour and Fragrance Compounds

Claisen, Cope and Related Rearrangements in the Synthesis of Flavour and Fragrance Compounds

Stereochemistry of [2,3]Sigmatropic Rearrangements

Towards a New Synthetic Entry into theIboga-Alkaloid Family

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