Mechanistic and Computational Studies of Oxidatively-Induced Aryl鈭扖F3 Bond-Formation at Pd: Rational Design of Room Temperature Aryl Trifluoromethylation

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• 作者：Nicholas D. Ball ; J. Brannon Gary ; Yingda Ye ; Melanie S. Sanford
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：May 18, 2011
• 年：2011
• 卷：133
• 期：19
• 页码：7577-7584
• 全文大小：1073K
• 年卷期：v.133,no.19(May 18, 2011)
• ISSN：1520-5126

文摘

This article describes the rational design of first generation systems for oxidatively induced Aryl鈭扖F₃ bond-forming reductive elimination from Pd^II. Treatment of (dtbpy)Pd^II(Aryl)(CF₃) (dtbpy = di-tert-butylbipyridine) with NFTPT (N-fluoro-1,3,5-trimethylpyridinium triflate) afforded the isolable Pd^IV intermediate (dtbpy)Pd^IV(Aryl)(CF₃)(F)(OTf). Thermolysis of this complex at 80 掳C resulted in Aryl鈭扖F₃ bond-formation. Detailed experimental and computational mechanistic studies have been conducted to gain insights into the key reductive elimination step. Reductive elimination from this Pd^IV species proceeds via pre-equilibrium dissociation of TfO^{鈭?/sup> followed by Aryl鈭扖F₃ coupling. DFT calculations reveal that the transition state for Aryl鈭扖F₃ bond formation involves the CF₃ acting as an electrophile with the Aryl ligand serving as a nucleophilic coupling partner. These mechanistic considerations along with DFT calculations have facilitated the design of a second generation system utilizing the tmeda (N,N,N鈥?N鈥?tetramethylethylenediamine) ligand in place of dtbpy. The tmeda complexes undergo oxidative trifluoromethylation at room temperature.}