Unveiling the Ionic Diels–Alder Reactions within the Molecular Electron Density Theory
The ionic Diels–Alder (I-DA) reactions of a series of six iminium cations with cyclopentadiene have been studied within the Molecular Electron Density Theory (MEDT). The superelectrophilic character of iminium cations, ω > 8.20 eV, accounts for the high reactivity of these species participating i...
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MDPI AG
2021-06-01
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| Series: | Molecules |
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| Online Access: | https://www.mdpi.com/1420-3049/26/12/3638 |
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| author | Luis R. Domingo Mar Ríos-Gutiérrez María José Aurell |
| author_facet | Luis R. Domingo Mar Ríos-Gutiérrez María José Aurell |
| author_sort | Luis R. Domingo |
| collection | DOAJ |
| description | The ionic Diels–Alder (I-DA) reactions of a series of six iminium cations with cyclopentadiene have been studied within the Molecular Electron Density Theory (MEDT). The superelectrophilic character of iminium cations, ω > 8.20 eV, accounts for the high reactivity of these species participating in I-DA reactions. The activation energies are found to be between 13 and 20 kcal·mol<sup>−1</sup> lower in energy than those associated with the corresponding Diels–Alder (DA) reactions of neutral imines. These reactions are low <i>endo</i> selective as a consequence of the cationic character of the TSs, but highly regioselective. Solvents have poor effects on the relative energies, and an unappreciable effect on the geometries. In acetonitrile, the activation energies increase slightly as a consequence of the better solvation of the iminium cations than the cationic TSs. Electron localization function (ELF) topological analysis of the bonding changes along the I-DA reactions shows that they are very similar to those in polar DA reactions. The present MEDT study establishes that the global electron density transfer (GEDT) taking place at the TSs of I-DA reactions, and not steric (Pauli) repulsions such as have been recently proposed, are responsible for the features of these types of DA reactions. |
| first_indexed | 2024-03-10T10:25:24Z |
| format | Article |
| id | doaj.art-67735fcfd39543cfa333cc3d06afff81 |
| institution | Directory Open Access Journal |
| issn | 1420-3049 |
| language | English |
| last_indexed | 2024-03-10T10:25:24Z |
| publishDate | 2021-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Molecules |
| spelling | doaj.art-67735fcfd39543cfa333cc3d06afff812023-11-22T00:04:17ZengMDPI AGMolecules1420-30492021-06-012612363810.3390/molecules26123638Unveiling the Ionic Diels–Alder Reactions within the Molecular Electron Density TheoryLuis R. Domingo0Mar Ríos-Gutiérrez1María José Aurell2Department of Organic Chemistry, University of Valencia, Dr. Moliner 50, E-46100 Valencia, SpainDepartment of Organic Chemistry, University of Valencia, Dr. Moliner 50, E-46100 Valencia, SpainDepartment of Organic Chemistry, University of Valencia, Dr. Moliner 50, E-46100 Valencia, SpainThe ionic Diels–Alder (I-DA) reactions of a series of six iminium cations with cyclopentadiene have been studied within the Molecular Electron Density Theory (MEDT). The superelectrophilic character of iminium cations, ω > 8.20 eV, accounts for the high reactivity of these species participating in I-DA reactions. The activation energies are found to be between 13 and 20 kcal·mol<sup>−1</sup> lower in energy than those associated with the corresponding Diels–Alder (DA) reactions of neutral imines. These reactions are low <i>endo</i> selective as a consequence of the cationic character of the TSs, but highly regioselective. Solvents have poor effects on the relative energies, and an unappreciable effect on the geometries. In acetonitrile, the activation energies increase slightly as a consequence of the better solvation of the iminium cations than the cationic TSs. Electron localization function (ELF) topological analysis of the bonding changes along the I-DA reactions shows that they are very similar to those in polar DA reactions. The present MEDT study establishes that the global electron density transfer (GEDT) taking place at the TSs of I-DA reactions, and not steric (Pauli) repulsions such as have been recently proposed, are responsible for the features of these types of DA reactions.https://www.mdpi.com/1420-3049/26/12/3638ionic Diels–Alder reactionsMolecular Electron Density Theoryiminium cationssuperelectrophilesglobal electron density transferasynchronicity |
| spellingShingle | Luis R. Domingo Mar Ríos-Gutiérrez María José Aurell Unveiling the Ionic Diels–Alder Reactions within the Molecular Electron Density Theory Molecules ionic Diels–Alder reactions Molecular Electron Density Theory iminium cations superelectrophiles global electron density transfer asynchronicity |
| title | Unveiling the Ionic Diels–Alder Reactions within the Molecular Electron Density Theory |
| title_full | Unveiling the Ionic Diels–Alder Reactions within the Molecular Electron Density Theory |
| title_fullStr | Unveiling the Ionic Diels–Alder Reactions within the Molecular Electron Density Theory |
| title_full_unstemmed | Unveiling the Ionic Diels–Alder Reactions within the Molecular Electron Density Theory |
| title_short | Unveiling the Ionic Diels–Alder Reactions within the Molecular Electron Density Theory |
| title_sort | unveiling the ionic diels alder reactions within the molecular electron density theory |
| topic | ionic Diels–Alder reactions Molecular Electron Density Theory iminium cations superelectrophiles global electron density transfer asynchronicity |
| url | https://www.mdpi.com/1420-3049/26/12/3638 |
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