Catalysis of the Claisen Rearrangement of Aliphatic Allyl Vinyl Ethers

Hiersemann, Martin; Abraham, Lars

doi:10.1002/1099-0690(200205)2002:9<1461::aid-ejoc1461>3.0.co;2-1

Cited by 125 publications

(39 citation statements)

References 78 publications

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“…A number of excellent reviews on the Claisen rearrangement have appeared. [34] Catalytic tandem processes involving Claisen rearrangement can be organized loosely into the following types: tandem pericylic processes, coupling and isomerization, and cyclization reactions.…”

Section: [33]-sigmatropic Rearrangementsmentioning

confidence: 99%

Toward a Symphony of Reactivity: Cascades Involving Catalysis and Sigmatropic Rearrangements

et al. 2014

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Catalysis and synthesis are intimately linked in modern organic chemistry. The synthesis of complex molecules is an ever evolving area of science. In many regards, the inherent beauty associated with a synthetic sequence can be linked to a certain combination of the creativity with which a sequence is designed and the overall efficiency with which the ultimate process is performed. In synthesis, as in other endeavors, beauty is very much in the eyes of the beholder.[**] It is with this in mind that we will attempt to review an area of synthesis that has fascinated us and that we find extraordinarily beautiful, namely the combination of catalysis and sigmatropic rearrangements in consecutive and cascade sequences.

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Section: [33]-sigmatropic Rearrangementsmentioning

confidence: 99%

Toward a Symphony of Reactivity: Cascades Involving Catalysis and Sigmatropic Rearrangements

et al. 2014

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“…This compound was subjected to our standard reaction conditions to afford 4 in a 34% yield, in addition to recovery of most of the remaining starting material (Scheme 2). Unable to undergo a tandem rearrangement and cyclization due to the presence of two ortho substituents, this substrate instead underwent a [3,3] rearrangement to afford compound 4, indicating that cationic gold(I) is capable of mediating the rearrangement. We next conducted the reactions shown in Scheme 3 in order to confirm the mechanism shown in Scheme 1 for the one-pot reaction.…”

Section: Methodsmentioning

confidence: 99%

“…2 Though traditionally this reaction is conducted thermally at high temperatures, a large number of catalytic systems have been developed for both the aryl and aliphatic variants of the reaction. 2,3 In addition to carboncarbon bond formation, the product of the aryl Claisen rearrangement is well suited to undergo ring closure via an intramolecular addition reaction to give a dihydrobenzofuran (Scheme 1). As part of our continued interest in cationic gold species as effective Lewis acid catalysts, we sought to catalyze the synthesis of dihydrobenzofurans from allyl aryl ethers in a one-pot process.…”

mentioning

confidence: 99%

Gold(I)-Catalyzed Synthesis of Dihydrobenzofurans from Aryl Allyl Ethers

Reich¹,

Yang²,

Shi³

et al. 2006

Synlett

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“…We describe here the application of enantiopure 1 in catalyzing the aza-Cope rearrangement, achieving enantioselectivities for host-guest catalysis that are remarkable in view of the fact that the cavity bears no reactive functional groups. A series of prochiral enammonium tosylates (2a-g) were treated with catalytic amounts of (NMe 4 ) 12 [-1] to explore the possibility of asymmetric induction in the host-catalyzed aza-Cope rearrangement. High catalyst loadings were used to avoid precipitation of the catalyst-substrate complexes.…”

Section: Raymond and Coworkers Have Developed [Ga 4 L 6 ]mentioning

confidence: 99%

“…Ordinarily, coordinating groups on the substrate are required, driving complexation of a chiral Lewis acid. 12 Assembly 1 is able to render this pericyclic reaction enantioselective only by confining the reaction to a chiral space, rather than interacting specifically with a moiety on the substrate. This is an attractive feature of supramolecular reaction vessels and is an important virtue of this complementary catalytic strategy.…”

Section: Raymond and Coworkers Have Developed [Ga 4 L 6 ]mentioning

confidence: 99%

Enantioselective Catalysis of the Aza-Cope Rearrangement by a Chiral Supramolecular Assembly

2009

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Nanoscale molecular flasks have increasingly been used to promote novel reactivity or impart powerful selectivity through precise, noncovalent interactions with substrate molecules.Encapsulation of substrate molecules within these host structures may stabilize reactive species 1 or, conversely, promote substrate reactivity. 2 The confined environment within these supramolecular hosts has also been demonstrated to impart remarkable size and shape selectivity. Employing these supramolecular assemblies in asymmetric catalysis remains an important challenge.4 Chiral building blocks may be used to construct chiral supramolecular assemblies, in some cases generating additional elements of chirality during the assembly of these structures. While chiral supramolecular assemblies have been shown to carry out enantioselective stoichiometric reactions, or catalyze reactions with modest ee, a highly enantioselective catalytic transformation has not yet been demonstrated. 5 We now report such catalysis. 12-assembly 1, a self-assembling supramolecular structure. 6 In collaboration with the Bergman group, this cluster has been shown capable of catalyzing a variety of chemical transformations with low catalyst loadings and enzyme-like kinetics, including the aza-Cope rearrangement and the hydrolysis of orthoformates and acetals.7 Importantly, 1 is chiral due to the three bidentate catecholates coordinating each gallium center (Figure 1). Mechanical coupling between the four vertices enforces the same helical configuration ( or ) at each metal center.8 As a result, two enantiomeric forms of 1 exist,  and . Though 1 is synthesized as the racemate, addition of (-)-N'-methylnicotinium iodide (S-nicI) causes the spontaneous resolution of the two enantiomers, allowing access to pure -(S-nic  1, where  denotes encapsulation) and pure -(S-nic  1). Ion exchange chromatography allows isolation of each enantiomer as the tetramethylammonium salt. 9For this study, the aza-Cope rearrangement of enammonium substrates was selected (Figure 2) to evaluate 1 as an enantioselective catalyst.9c Encapsulation of enammonium substrates within 1 enforces a reactive conformation. The product iminium ions are vulnerable to hydrolysis, producing neutral aldehydes which are not encapsulated in 1. As long as R 1 ≠ R 2 , the rearrangement generates a chiral center and potentially enantioselective within chiral assembly 1. Since obtaining suitable quantities of enantiopure K 12 1 is not practical, reactivity compatible with (NMe 4 ) 12 1 is required. . Enammonium substrates 2 are more tightly bound than NMe 4 + , enabling efficient catalysis within (NMe 4 ) 12 1. We describe here the application of enantiopure 1 in catalyzing the aza-Cope rearrangement, achieving enantioselectivities for host-guest catalysis that are remarkable in view of the fact that the cavity bears no reactive functional groups.

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Catalysis of the Claisen Rearrangement of Aliphatic Allyl Vinyl Ethers

Cited by 125 publications

References 78 publications

Toward a Symphony of Reactivity: Cascades Involving Catalysis and Sigmatropic Rearrangements

Toward a Symphony of Reactivity: Cascades Involving Catalysis and Sigmatropic Rearrangements

Gold(I)-Catalyzed Synthesis of Dihydrobenzofurans from Aryl Allyl Ethers

Enantioselective Catalysis of the Aza-Cope Rearrangement by a Chiral Supramolecular Assembly

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