Transesterification. II. Esters of Strong Organic Acids

Bader, Alfred R.; Vogel, Henry A.

doi:10.1021/ja01136a006

Cited by 16 publications

(8 citation statements)

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“…The subsequent macrolactonization of purified 54 was undertaken via a broadly applicable transesterification protocol for β-ketoesters as originally described by Bader and coworkers. 40 The mechanism of this reaction has been studied, and suggests a concerted elimination of alcohol which is consistent with a unimolecular process. Formation of an intermediate acylketene is followed by nucleophilic addition.…”

Section: Resultsmentioning

confidence: 88%

Studies for the Total Synthesis of Amphidinolide P

Williams

Myers

et al. 2013

J. Org. Chem.

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A convergent, enantiocontrolled total synthesis of the 15-membered macrolide, amphidinolide P, is described. The synthesis utilizes three nonracemic components for an efficient assembly of the macrolactone in 12 steps via the longest linear pathway. Key developments include studies of the Hosomi–Sakurai reaction for the formation of the C6–C7 bond, a “ligandless” palladium-mediated Stille cross-coupling of the vinylic stannane 4 and the alkenyl bromide 5 to produce a highly functionalized dienol, and a thermally induced, intramolecular lactonization via the late-stage formation of an intermediate α-acylketene.

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Section: Resultsmentioning

confidence: 88%

Studies for the Total Synthesis of Amphidinolide P

Williams

Myers

et al. 2013

J. Org. Chem.

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“…β-Ketoesters as well as esters derived from malonates or oxalates, for example, are also more prone to transesterification reactions in solution. 211 Indeed, acetoacetic acid is 10 times stronger than acetic acid, so its conjugated base is more stable and the corresponding ester bond is weaker, leading to easier transesterification. 211 Oxalates' reactivity toward transesterification is explained exclusively by inductive effects.…”

Section: Exchangeable Bonds With An Associative Mechanismmentioning

confidence: 99%

“…211 Indeed, acetoacetic acid is 10 times stronger than acetic acid, so its conjugated base is more stable and the corresponding ester bond is weaker, leading to easier transesterification. 211 Oxalates' reactivity toward transesterification is explained exclusively by inductive effects. For βketoesters and malonates, a stabilized cyclic intermediate was proposed to explain the reactivity of the other aforementioned species, though inductive effects also play a significant role (Scheme 26).…”

Section: Exchangeable Bonds With An Associative Mechanismmentioning

confidence: 99%

Neighboring Group Participation and Internal Catalysis Effects on Exchangeable Covalent Bonds: Application to the Thriving Field of Vitrimer Chemistry

et al. 2021

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Vitrimers constitute a fascinating class of polymer materials which make the link between the historically opposed 3D networks (thermosets) and linear polymers (thermoplastics). Their chemical resistance, reshaping ability and unique rheological behavior upon heating make them promising for future applications in industry. However many vitrimers require the use of high catalyst loadings, which raises concerns for their durability, and limits their potential applications. To cope with this issue, internal catalysis and neighboring group participation (NGP) can be used to enhance the reshaping ability of such materials. A few studies report the effect of activating groups on the exchange reactions in vitrimers. Nevertheless, knowledge on this topic remains scarce, although research on vitrimers would greatly benefit from NGP already known in organic chemistry. The present perspective article presents the different types of exchangeable bonds implemented in vitrimers and discusses chemical groups known to have or potentially capable of an enhancing effect on exchange reactions. This analysis is underpinned by a thorough mechanistic discussion of the various exchangeable bonds presented.

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“…45 (45) 0 °Ratio indicated is nitrile: bromoester: zinc. 6 The first quantity is time of reaction in mins. ; the second quantity (in parentheses) is time of hydrolysis in mins."…”

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confidence: 99%