Catalyzing Pyramidal Inversion: Configurational Lability of P-Stereogenic Phosphines via Single Electron Oxidation

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• 作者：Kyle D. Reichl ; Daniel H. Ess ; Alexander T. Radosevich
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：June 26, 2013
• 年：2013
• 卷：135
• 期：25
• 页码：9354-9357
• 全文大小：313K
• 年卷期：v.135,no.25(June 26, 2013)
• ISSN：1520-5126

文摘

We report that pyramidal inversion of trivalent phosphines may be catalyzed by single electron oxidation. Specifically, a series of P-stereogenic (aryl)methylphenyl phosphines are shown to undergo rapid racemization at ambient temperature when exposed to catalytic quantities of a single electron oxidant in solution. Under these conditions, transient phosphoniumyl radical cations (R<sub>3sub>P<sup>鈥?sup>) are formed, and computational models indicate that the pyramidal inversion barriers for these open-shell intermediates are on the order of 5 kcal/mol. The observed 10<sup>20sup>-fold rate enhancement over uncatalyzed pyramidal inversion opens new opportunities for the dynamic stereochemistry of phosphines and may hold additional implications for the configurational stability of P-stereogenic phosphine ligands on high-valent oxidizing transition metals.