Quantitative preparation and enthalpy of rearrangement of the sec-butyl cation

Bittner, Edward W.; Arnett, E. M.; Saunders, Martin

doi:10.1021/ja00428a072

Cited by 31 publications

(15 citation statements)

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“…Because the physical characteristics, relative reactivities and relative stabilities of aliphatic carbenium ions in the condensed phase depend very little on media change, 19 the properties of these ionic species in the gas phase are relevant to those in the liquid phase. A comparison of mass spectrometric and calorimetric measurements shows no essential change in enthalpy trends for isomeric gas-phase secondary and tertiary carbenium ions over those in the condensed phase.…”

Section: Introductionmentioning

confidence: 99%

Gas-phase electrophilic aromatic substitution of electron-rich and electron-deficient aromatic compounds

Holman¹,

Eary²,

Whittle³

et al. 1998

J. Chem. Soc., Perkin Trans. 2

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The first step in gas-phase electrophilic aromatic substitution (EAS) reactions of alkyl carbenium ions with fluoro-, chloro-and bromo-benzene, furan, thiophene and pyrrole, has been investigated by using high-pressure, chemical-ionization and tandem mass spectrometry (MS/MS). Collisionally activated dissociation (CAD) and tandem mass spectrometry, MS/MS, have been utilized for ion-structure determination. The coexistence of and complexes in these reactions is a means of rationalizing the results. It has been established that the extent of -complex formation decreases with an increased capability of the aromatic to donate electron density. Semi-empirical computations indicate that as -electron density within the aromatic moiety increases, the energy difference between the more stable complex and the complex increases, which is also consistent with experimental observations. The extent of bonding between the alkyl group and the aromatic of certain complexes is sufficiently weak that isomerization of the alkyl moiety takes place.

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Section: Introductionmentioning

confidence: 99%

Gas-phase electrophilic aromatic substitution of electron-rich and electron-deficient aromatic compounds

Holman¹,

Eary²,

Whittle³

et al. 1998

J. Chem. Soc., Perkin Trans. 2

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“…On the basis of the previous reports on gold-catalyzed enynes cyclization , and the mechanism of Kornblum oxidation, a plausible mechanism is outlined in Scheme . Initially, coordination of cationic Au I complex to the alkyne moiety of 1a forms intermediate I , followed by a 6-endo-dig cyclization to give intermediate II because the benzene ring and electron-rich cyclopropane can stabilize the formed carbon cation. , Then, intermediate II is combined with external 3,5-dibromo-pyridine N -oxide to form a reactant complex III , which leads to ring-opening of ACP to form intermediate IV (electrophilically assisted nucleophilic ring opening) . Finally, deprotonation utilizing the released 3,5-dibromo-pyridine and protodeauration sequences occur, thus furnishing the desired naphthylacetaldehyde 3a .…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Polysubstituted Polycyclic Aromatic Hydrocarbons by Gold-Catalyzed Cyclization–Oxidation of Alkylidenecyclopropane-Containing 1,5-Enynes

Wei

Shi

2017

ACS Catal.

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A gold-catalyzed tandem cyclization–oxidation of alkylidenecyclopropane-containing 1,5-enynes with 3,5-dibromo-pyridine N-oxide via a noncarbene model was developed, providing a range of synthetically valuable and useful arylacetaldehyde derivatives in moderate to good yields without oxidation of alkynes. Moreover, the corresponding aldehydes can be further transformed into polycyclic aromatic hydrocarbons in the presence of a catalytic amount of Lewis acid In(OTf)3. The reaction represents an example of gold-catalyzed halide-free Kornblum-type oxidation through the oxidation of the cyclopropane moiety.

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“…Die Reaktionswarme der Isomerisierung des sek-Butylkations 17 zum tert-Butylkation 6 wurde in SbFS/SOZCIF zu -60 kJ . mol-' bestimmt [13], fur die Isomerisierung des 4-Methylnorbornylkations 24 zum 2-Methylnorbornylkation 8 fand man -28 kJ.mo1-l [14]. Diese Werte kommen auch quantitativ den Gasphasen-Daten (Tabelle 1) nahe und bestatigen den geringen Stabilitatsunterschied zwischeii sekundaren und tertiaren Norbornylkationen.…”

Section: Carbokationen I N Der Gasphaseunclassified

Umlagerungen von Carbokationen

Kirme

1982

Chemie in nserer Zeit

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Quantitative preparation and enthalpy of rearrangement of the sec-butyl cation

Cited by 31 publications

References 1 publication

Gas-phase electrophilic aromatic substitution of electron-rich and electron-deficient aromatic compounds

Gas-phase electrophilic aromatic substitution of electron-rich and electron-deficient aromatic compounds

Synthesis of Polysubstituted Polycyclic Aromatic Hydrocarbons by Gold-Catalyzed Cyclization–Oxidation of Alkylidenecyclopropane-Containing 1,5-Enynes

Umlagerungen von Carbokationen

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