期刊
MOLECULES
卷 25, 期 11, 页码 -出版社
MDPI
DOI: 10.3390/molecules25112535
关键词
Diels-Alder; Lewis acid; catalysis; molecular electron density theory; relation mechanism
资金
- Ministry of Economy and Competitiveness (MINECO) of the Spanish Government [CTQ2016-78669-P]
- FONDECYT-Chile through Fondecyt [1180348]
- European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant [84618]
The effects of metal-based Lewis acid (LA) catalysts on the reaction rate and regioselectivity in polar Diels-Alder (P-DA) reactions has been analyzed within the molecular electron density theory (MEDT). A clear linear correlation between the reduction of the activation energies and the increase of the polar character of the reactions measured by analysis of the global electron density transfer at the corresponding transition state structures (TS) is found, a behavior easily predictable by analysis of the electrophilicity omega and nucleophilicity N indices of the reagents. The presence of a strong electron-releasing group in the diene changes the mechanism of these P-DA reactions from a two-stage one-step to a two-step one via formation of a zwitterionic intermediate. However, this change in the reaction mechanism does not have any chemical relevance. This MEDT study makes it possible to establish that the more favorable nucleophilic/electrophilic interactions taking place at the TSs of LA catalyzed P-DA reactions are responsible for the high acceleration and complete regioselectivity experimentally observed.
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