The Stereochemistry of Electrophilic Additions to Olefins and Acetylenes

Fahey, Robert C.

doi:10.1002/9780470147122.ch4

Cited by 87 publications

(4 citation statements)

References 334 publications

(157 reference statements)

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“…For additions of HCl to simple alkenes such as isobutene in nitromethane, it is observed that free chloride suppresses the rate, the opposite of observations in Ad E 3 mechanisms . Also, the addition of HCl to cis - and trans -1-phenylpropene in nitromethane affords the syn-addition adduct as the major product . These observations weigh strongly against a concerted Ad E 3 mechanism. …”

Section: Resultsmentioning

confidence: 93%

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Solvation Dynamics and the Nature of Reaction Barriers and Ion-Pair Intermediates in Carbocation Reactions

Roytman

Singleton

2020

J. Am. Chem. Soc.

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Additions of acids to 1,3-dienes are conventionally understood as involving discrete intermediates that undergo an ordinary competition between subsequent pathways to form the observed products. The combined experimental, computational, and dynamic trajectory study here suggests that this view is incorrect, and that solvation dynamics plays a critical role in the mechanism. While implicit solvent models were inadequate, QM/QM′ trajectories in explicit solvent provide an accurate prediction of the experimental selectivity in the addition of HCl to 1,3-pentadiene. Trajectories initiated from a protonation saddle point on the potential of mean force surface are predominantly unproductive due to a gating effect of solvation that allows diene protonation only when the incipient ion pair is neither too solvent-stabilized nor too little. Protonation then leads to relatively unsolvated ion pairs, and a majority of these collapse rapidly to the 1,2-product, without barrier and without achieving equilibrium solvation as intermediates. The remainder decay slowly, at a rate consistent with equilibrium solvation as true intermediates, affording a mixture of addition products. Overall, an accurate description of the nature and pathway selectivity of the ion pair intermediates in carbocation reactions must allow for species lacking equilibrium solvation. Potential reinterpretations of a series of historically notable observations in carbocation reactions are discussed.

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Section: Resultsmentioning

confidence: 93%

“…25a Also, the addition of HCl to cis-and trans-1phenylpropene in nitromethane affords the syn-addition adduct as the major product. 26 These observations weigh strongly against a concerted Ad E 3 mechanism.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Solvation Dynamics and the Nature of Reaction Barriers and Ion-Pair Intermediates in Carbocation Reactions

Roytman

Singleton

2020

J. Am. Chem. Soc.

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“…These reactions are intrinsically sluggish when compared to their intramolecular counterparts due to a higher reaction entropy. 34 This low reactivity is often overcome using either a super-stoichiometric amount of the acid partner or directly as the solvent; resulting in poor atom-economy. For example, in two separate publications by Braddock et al the tetramethylguanidine (TMG) and iso-amarine were used to catalyze the bromoacetoxylation of styrene ( Scheme 3a ).…”

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confidence: 99%

Solvent and catalyst-free bromofunctionalization of olefins using a mechanochemical approach

Wong

Yeung

2021

RSC Adv.

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“…It is believed that the nucleophilic carboxylate groups could interact with olefins reversibly and increase the reactivity of olefins toward electrophilic halogenations by increasing the olefin’s HOMO energy . Thus, tethering the olefins and carboxylic acids would preorganize them, and the halolactonization would be facilitated because of the decreased entropy …”

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confidence: 99%

Zwitterion-Catalyzed Intermolecular Bromoesterifications

Lam

et al. 2020

Org. Lett.

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Intermolecular haloesterification is an important class of transformations. The resulting products are valuable building blocks. However, it is often necessary to use super-stoichiometric amount of acid in order to compensate the low reactivity. Herein, we report a zwitterion-catalyzed intermolecular bromoesterification using acid and olefin in an equimolar ratio. Mechanistic study revealed that the charge pair in the zwitterion works synergistically in activating both NBS and carboxylic acid.

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The Stereochemistry of Electrophilic Additions to Olefins and Acetylenes

Cited by 87 publications

References 334 publications

Solvation Dynamics and the Nature of Reaction Barriers and Ion-Pair Intermediates in Carbocation Reactions

Solvation Dynamics and the Nature of Reaction Barriers and Ion-Pair Intermediates in Carbocation Reactions

Solvent and catalyst-free bromofunctionalization of olefins using a mechanochemical approach

Zwitterion-Catalyzed Intermolecular Bromoesterifications

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