Theoretical Gas‐Phase Stabilities of α‐Trimethylsilyl‐Substituted Tertiary Carbenium Ions

Grunenberg, Jörg; Dickner, Tim

doi:10.1002/ejoc.200300273

Cited by 5 publications

(2 citation statements)

References 45 publications

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“…Compared to the β-and γ-Si effects, the hyperconjugation effect of silicon-carbon bonds in the α positions of carbocations is less pronounced, due to the diminished electron density of the longer C-Si bonds. A recent computational study by Grunenberg et al [6] revealed the theoretical gas-phase stabilities of α-trimethylsilyl (TMS)-substituted tertiary carbenium ions: the thermodynamic stabilization of a carbenium ion by a single α-TMS group is weaker than that by a tert-butyl group, but much stronger than that by a hydrogen-carbon bond. It is also greater than the stabilization by a methyl group (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Removable Silyl Group as a “Masked Proton” in Oxy‐2‐oxonia(azonia)‐Cope Rearrangement: Applications in Stereoselective Total Synthesis of Natural Macrolides

Zou

Zhou

et al. 2015

Eur J Org Chem

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In the presence of a Lewis acid, trimethylsilyl‐substituted β,γ‐unsaturated ketones and aldehydes (imines) undergo nucleophilic addition to produce zwitterionic intermediates, followed by oxy‐2‐oxonia(azonia)‐Cope rearrangements to give homoallylic esters (amides). In the case of TMS‐containing 2‐vinylcycloalkanones, the process results in ring‐enlargement, providing 10‐ to 16‐membered lactones. This protocol was applied to the total synthesis of (R)‐phoracantholide I.

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Section: Introductionmentioning

confidence: 99%

Removable Silyl Group as a “Masked Proton” in Oxy‐2‐oxonia(azonia)‐Cope Rearrangement: Applications in Stereoselective Total Synthesis of Natural Macrolides

Zou

Zhou

et al. 2015

Eur J Org Chem

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“…Closely related to carbenes, and of relevance to the present study, are carbenium and/or carbonium ions. Some of these have also been studied theoretically – and experimentally, either because of their involvement in atmospheric and/or combustion chemistry or because of their importance as useful intermediates in chemical reactions. , However, we are not aware of any reported studies of the proton capture reaction by carbenes to form carbenium ions (i.e., to determine their proton attachment energies). Such information is of intrinsic interest, but it is also relevant to modeling combustion processes, including, e.g., reactions of coal combustion products with flue gas components on activated carbon.…”

Section: Introductionmentioning

confidence: 99%

Carbene Proton Attachment Energies: Theoretical Study

et al. 2008

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The geometries and electronic energies of six singlet carbenes, with methyl and phenyl substituents, and the corresponding carbenium ions were obtained using several density functional theory (DFT) variants and the second-order Møller-Plesset method for electron correlation and compared with G3 results, with the aim to determine a relatively low-cost computational protocol that is sufficiently accurate for the specific molecules and ions of interest. Some additional calculations were performed at the CCSD(T) level. Results for diphenylcarbene, methylphenylcarbene, and their cations, which were not previously investigated by ab initio methods, are reported as are calculations on methylene, methylcarbene, dimethylcarbene, and phenylcarbene. The MPW3LYP/6-311+G(d,p) hybrid DFT level was found to give results that were in close agreement with those obtained using G3 theory, with a mean absolute deviation (MAD) of 1.76 kcal/mol for the calculated proton attachment energies (PAEs). Equilibrium geometries obtained with this method were compared with those obtained at the MP2/6-311G(d,p) level of theory, and bond lengths and bond angles had MADs of 0.005 A and 1.0 degrees, respectively. Harmonic vibrational frequencies of all the carbene molecules and the corresponding ions were computed to verify that the stationary points were true minima, to obtain zero-point corrected energies, to assist in infrared studies of the molecules. The recommended combination of method and basis set is expected to be a useful framework that uses modest amounts of computer resources to obtain usable thermochemical data on moderate-sized hydrocarbons and hydrocarbon cations, including coal-mimetic species.

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The 1‐Phenyl‐1‐(trimethylsilyl)ethyl Cation: An NMR Spectroscopic and Computational Study of the α‐Silyl Effect in Benzyl Cations

et al. 2012

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The 1‐phenyl‐1‐(trimethylsilyl)ethyl cation is generated as a persistent species in solution and characterized experimentally by 1H, 13C, and 29Si NMR spectroscopy. The α‐silyl effect is elucidated by comparison with other benzyl cations, such as cumyl and 1‐phenylethyl cations. Concomitant quantum chemical calculations of structures, relative thermodynamic stabilities, chemical shifts, and the harmonic oscillator model of aromaticity (HOMA) indices are congruent with the analysis of the experimental NMR spectroscopy results; therefore, we conclude that, in benzyl cations, the α‐silyl substituent is stabilizing with respect to H, but destabilizing relative to a methyl group.

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Theoretical Gas‐Phase Stabilities of α‐Trimethylsilyl‐Substituted Tertiary Carbenium Ions

Cited by 5 publications

References 45 publications

Removable Silyl Group as a “Masked Proton” in Oxy‐2‐oxonia(azonia)‐Cope Rearrangement: Applications in Stereoselective Total Synthesis of Natural Macrolides

Removable Silyl Group as a “Masked Proton” in Oxy‐2‐oxonia(azonia)‐Cope Rearrangement: Applications in Stereoselective Total Synthesis of Natural Macrolides

Carbene Proton Attachment Energies: Theoretical Study

The 1‐Phenyl‐1‐(trimethylsilyl)ethyl Cation: An NMR Spectroscopic and Computational Study of the α‐Silyl Effect in Benzyl Cations

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