Electrophilic Reactivity of a 2-Azaallenium and of a 2-Azaallylium Ion

Abstract

The rate constants for the reactions of the 2‐azaallenium ion 1b+, the 2‐azaallylium ion 2a+ and the iminium ion 3+ with different nucleophiles were determined by 1H NMR spectroscopy. By correlation with the Linear Free Enthalpy Relationship (LFER) lg k20°C = s (E + N), developed by Mayr and Patz, the electrophilicity parameters E(1b+) = ‐3.7, E(2a+) ≈︁ ‐16 and E(3+) = ‐10.43 were obtained. They show that the relative reactivities of these ions are approximately 1012:1:106. Quantum chemical calculations (ab initio, DFT) of the methyl anion affinities for the ions 1b+,2a+ and3+ are in agreement with the experimental E values. The X‐ray structure of 3+·CF3SO 3− is reported for the first time; it shows no strong interaction between the cation and the anion.

Quantum Mechanics and Machine Learning Synergies: Graph Attention Neural Networks to Predict Chemical Reactivity

“…Methyl cation affinity (MCA) is defined as the energy difference resulting from combining a methyl cation with a nucleophile; similarly, methyl anion affinity (MAA) is defined as the energy difference resulting from combining a methyl anion with an electrophile (Figure a). Mayr, Ofial, Zipse, and others have shown that MCA and MAA correlate with the experimentally measured nucleophilicities and electrophilicities on a relatively small range of reactivity − (∼30 orders of magnitude , ).…”

Reactivity of δ ‐Functionalized Para ‐Quinone Methides in Nucleophilic Addition Reactions

“…We used quantum‐chemical calculations to unravel the seemingly unsystematic δ ‐FG effects on the electrophilicity of p QMs 1 . Previously, the linear correlation of Mayr electrophilicities E with methyl anion affinities (MAAs) [ 53–55 ] was shown to enable the prediction of electrophilic reactivities of typical Michael acceptors, including a series of δ ‐aryl‐ p QMs and ortho ‐quinone methides when involving the continuum solvation model (SMD) in the MAA calculations. [ 56,57 ] Analogously, we calculated [ 58,59 ] the MAAs as the Gibbs reaction energies Δ G R for the 1,6‐Michael addition of a methyl anion to the δ ‐FG‐ p QMs 1a – 1g at the SMD(DMSO) [ 60 ] /B3LYP/6–311++G(3df,2pd)//B3LYP/6–31G(d,p) level of theory [ 61–63 ] (Figure 6a).…”

Methyl Anion Affinities of the Canonical Organic Functional Groups

“…Subsequent work focused on individual functional groups but no attempt was made to correlate MAA with Mayr E for both neutral and cationic electrophiles. At higher levels of theory (MP2 and B3LYP), calculated MAAs also correlate linearly with Mayr electrophilicity for other classes of electrophiles: diarylallyl , and azacarbenium ions . Mayr and coworkers have also shown that neutral electrophiles such as ketones, Michael acceptors, and nitroarenes give good linear correlation between calculated MAAs and Mayr E .…”