Oxidative <i>N</i>-Dealkylation of <i>N</i>,<i>N</i>-Dimethylanilines by Non-Heme Manganese Catalysts
Non-heme manganese(II) complexes [(IndH)Mn<sup>II</sup>Cl<sub>2</sub>] (<b>1</b>) and [(N4Py*)Mn<sup>II</sup>(CH<sub>3</sub>CN)](ClO<sub>4</sub>)<sub>2</sub> (<b>2</b>) with tridentate isoindoline and pen...
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MDPI AG
2023-01-01
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| Online Access: | https://www.mdpi.com/2073-4344/13/1/194 |
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| author | Bashdar I. Meena Dóra Lakk-Bogáth Patrik Török József Kaizer |
| author_facet | Bashdar I. Meena Dóra Lakk-Bogáth Patrik Török József Kaizer |
| author_sort | Bashdar I. Meena |
| collection | DOAJ |
| description | Non-heme manganese(II) complexes [(IndH)Mn<sup>II</sup>Cl<sub>2</sub>] (<b>1</b>) and [(N4Py*)Mn<sup>II</sup>(CH<sub>3</sub>CN)](ClO<sub>4</sub>)<sub>2</sub> (<b>2</b>) with tridentate isoindoline and pentadentate polypyridyl ligands (IndH = 1,3-bis(2′-pyridylimino)isoindoline; N4Py* = <i>N</i>,<i>N</i>-bis(2-pyridylmethyl)-1,2- di(2-pyridyl)ethylamine) proved to be suitable to catalyze the oxidative demethylation of <i>N</i>,<i>N</i>-dimethylaniline (DMA) with various oxidants such as <i>tert</i>-butyl hydroperoxide (TBHP), peracetic acid (PAA), and <i>meta</i>-chloroperoxybenzoic acid (mCPBA), resulting <i>N</i>-methylaniline (MA) as a main product with <i>N</i>-methylformanilide (MFA) as a result of a free-radical chain process under air. The effect of electron-donating and electron-withdrawing substituents on the aromatic ring on the relative reactivity of the substrates and on the product composition (MA/MFA) was also studied and showed a significant impact on the catalytic <i>N</i>-demethylation reaction. Based on the Hammett correlation with <i>ρ</i> = −0.38 (PAA), −0.45 (mCPBA), and −0.63 (TBHP) for <b>1</b> and <i>ρ</i> = −0.38 (PAA) and −0.37 (mCPBA) for <b>2</b>, an electrophilic intermediate is suggested as the key oxidant. Furthermore, the spectral investigation (UV-Vis) resulted in direct evidence for the formation of a high-valent oxomanganese(IV) and a transient radical cation intermediate, <i>p</i>-Me-DMA<sup>•+</sup>, suggesting that the initial step in the manganese-catalyzed oxidations is a fast electron-transfer between the amine and the high valent oxometal species. The mechanisms of the subsequent steps are discussed. |
| first_indexed | 2024-03-09T13:13:47Z |
| format | Article |
| id | doaj.art-322847a7ba104a95821e6ed560d93d8c |
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| issn | 2073-4344 |
| language | English |
| last_indexed | 2024-03-09T13:13:47Z |
| publishDate | 2023-01-01 |
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| spelling | doaj.art-322847a7ba104a95821e6ed560d93d8c2023-11-30T21:38:40ZengMDPI AGCatalysts2073-43442023-01-0113119410.3390/catal13010194Oxidative <i>N</i>-Dealkylation of <i>N</i>,<i>N</i>-Dimethylanilines by Non-Heme Manganese CatalystsBashdar I. Meena0Dóra Lakk-Bogáth1Patrik Török2József Kaizer3Research Group of Bioorganic and Biocoordination Chemistry, University of Pannonia, H-8201 Veszprém, HungaryResearch Group of Bioorganic and Biocoordination Chemistry, University of Pannonia, H-8201 Veszprém, HungaryResearch Group of Bioorganic and Biocoordination Chemistry, University of Pannonia, H-8201 Veszprém, HungaryResearch Group of Bioorganic and Biocoordination Chemistry, University of Pannonia, H-8201 Veszprém, HungaryNon-heme manganese(II) complexes [(IndH)Mn<sup>II</sup>Cl<sub>2</sub>] (<b>1</b>) and [(N4Py*)Mn<sup>II</sup>(CH<sub>3</sub>CN)](ClO<sub>4</sub>)<sub>2</sub> (<b>2</b>) with tridentate isoindoline and pentadentate polypyridyl ligands (IndH = 1,3-bis(2′-pyridylimino)isoindoline; N4Py* = <i>N</i>,<i>N</i>-bis(2-pyridylmethyl)-1,2- di(2-pyridyl)ethylamine) proved to be suitable to catalyze the oxidative demethylation of <i>N</i>,<i>N</i>-dimethylaniline (DMA) with various oxidants such as <i>tert</i>-butyl hydroperoxide (TBHP), peracetic acid (PAA), and <i>meta</i>-chloroperoxybenzoic acid (mCPBA), resulting <i>N</i>-methylaniline (MA) as a main product with <i>N</i>-methylformanilide (MFA) as a result of a free-radical chain process under air. The effect of electron-donating and electron-withdrawing substituents on the aromatic ring on the relative reactivity of the substrates and on the product composition (MA/MFA) was also studied and showed a significant impact on the catalytic <i>N</i>-demethylation reaction. Based on the Hammett correlation with <i>ρ</i> = −0.38 (PAA), −0.45 (mCPBA), and −0.63 (TBHP) for <b>1</b> and <i>ρ</i> = −0.38 (PAA) and −0.37 (mCPBA) for <b>2</b>, an electrophilic intermediate is suggested as the key oxidant. Furthermore, the spectral investigation (UV-Vis) resulted in direct evidence for the formation of a high-valent oxomanganese(IV) and a transient radical cation intermediate, <i>p</i>-Me-DMA<sup>•+</sup>, suggesting that the initial step in the manganese-catalyzed oxidations is a fast electron-transfer between the amine and the high valent oxometal species. The mechanisms of the subsequent steps are discussed.https://www.mdpi.com/2073-4344/13/1/194bioinspired oxidationoxidative <i>N</i>-dealkylationMn-based catalystselectron transfer mechanism |
| spellingShingle | Bashdar I. Meena Dóra Lakk-Bogáth Patrik Török József Kaizer Oxidative <i>N</i>-Dealkylation of <i>N</i>,<i>N</i>-Dimethylanilines by Non-Heme Manganese Catalysts Catalysts bioinspired oxidation oxidative <i>N</i>-dealkylation Mn-based catalysts electron transfer mechanism |
| title | Oxidative <i>N</i>-Dealkylation of <i>N</i>,<i>N</i>-Dimethylanilines by Non-Heme Manganese Catalysts |
| title_full | Oxidative <i>N</i>-Dealkylation of <i>N</i>,<i>N</i>-Dimethylanilines by Non-Heme Manganese Catalysts |
| title_fullStr | Oxidative <i>N</i>-Dealkylation of <i>N</i>,<i>N</i>-Dimethylanilines by Non-Heme Manganese Catalysts |
| title_full_unstemmed | Oxidative <i>N</i>-Dealkylation of <i>N</i>,<i>N</i>-Dimethylanilines by Non-Heme Manganese Catalysts |
| title_short | Oxidative <i>N</i>-Dealkylation of <i>N</i>,<i>N</i>-Dimethylanilines by Non-Heme Manganese Catalysts |
| title_sort | oxidative i n i dealkylation of i n i i n i dimethylanilines by non heme manganese catalysts |
| topic | bioinspired oxidation oxidative <i>N</i>-dealkylation Mn-based catalysts electron transfer mechanism |
| url | https://www.mdpi.com/2073-4344/13/1/194 |
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