Metal-Free Phosphination and Continued Functionalization of Pyridine: A Theoretical Study
This study investigates the mechanism of metal-free pyridine phosphination with P(OEt)3, PPh3, and PAr2CF3 using density functional theory calculations. The results show that the reaction mechanism and rate-determining step vary depending on the phosphine and additive used. For example, phosphinatio...
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Veröffentlicht in: | Molecules (Basel, Switzerland) Switzerland), 2022-09, Vol.27 (17), p.5694 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | This study investigates the mechanism of metal-free pyridine phosphination with P(OEt)3, PPh3, and PAr2CF3 using density functional theory calculations. The results show that the reaction mechanism and rate-determining step vary depending on the phosphine and additive used. For example, phosphination of pyridine with P(OEt)3 occurs in five stages, and ethyl abstraction is the rate-determining step. Meanwhile, 2-Ph-pyridine phosphination with PPh3 is a four-step reaction with proton abstraction as the rate-limiting step. Energy decomposition analysis of the transition states reveals that steric hindrance in the phosphine molecule plays a key role in the site-selective formation of the phosphonium salt. The mechanism of 2-Ph-pyridine phosphination with PAr2CF3 is similar to that with PPh3, and analyses of the effects of substituents show that electron-withdrawing groups decreased the nucleophilicity of the phosphine, whereas aryl electron-donating groups increased it. Finally, TfO− plays an important role in the C–H fluoroalkylation of pyridine, as it brings weak interactions. |
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ISSN: | 1420-3049 1420-3049 |
DOI: | 10.3390/molecules27175694 |