DFT study on the reaction mechanism and regioselectivity for the [1,2]-anionic rearrangement of 2-benzyloxypyridine derivatives |
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Institution: | 1. Dipartimento di Scienze della Salute, Università di Catanzaro, Viale Europa, 88100 Catanzaro, Italy;2. Dipartimento di Scienze Chimiche, Università degli Studi di Catania, viale Andrea Doria, 6, 95125 Catania, Italy;3. Fondazione RI.MED, Via Bandiera 11, 90133 Palermo, Italy;4. Dipartimento di Farmacia, Università di Pisa, via Bonanno Pisano, 6, 56126 Pisa, Italy;5. Istituto di Biostrutture e Bioimagini—Consiglio Nazionale delle Ricerche (IBB—CNR), Via Paolo Gaifami, 18, 95126 Catania, Italy |
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Abstract: | The reaction mechanism of the 1,2]-anionic rearrangement of 2-benzyloxypyridines has been investigated using DFT calculations. Calculated results indicate that: the deprotonation step is relatively fast and the rearrangement step is the rate-determining step; electron-donating group on the benzene ring decreases the activation energy of the rearrangement, which correlates with an increase in reaction yield, while electron-withdrawing groups show the opposite effect. The rearrangement is calculated to proceed by way of an oxirane-like transition state that had previously been postulated as a transient intermediate. Furthermore, the mechanism for the rearrangement of 2-(benzyloxy)nicotinonitrile was discussed. The quick formation of the five membered ring intermediate leads to the predominant formation of 2-phenylfuro2,3-b]pyridin-3-amine. The calculation results indicate the possibilities of derivatizing the starting pyridyl ether as well as facilitating the rearrangement reaction by adding an appropriate electron-donating group on the benzene ring or electron-withdrawing group on the pyridine ring for future studies. |
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