Gold-Catalyzed Oxidative Coupling of Arylsilanes and Arenes: Origin?of Selectivity and Improved Precatalyst
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- 作者：Liam T. Ball ; Guy C. Lloyd-Jones ; Christopher A. Russell
- 刊名：Journal of the American Chemical Society
- 出版年：2014
- 出版时间：January 8, 2014
- 年：2014
- 卷：136
- 期：1
- 页码：254-264
- 全文大小：657K
- ISSN：1520-5126
文摘
The mechanism of gold-catalyzed coupling of arenes with aryltrimethylsilanes has been investigated, employing an improved precatalyst (thtAuBr3) to facilitate kinetic analysis. In combination with linear free-energy relationships, kinetic isotope effects, and stoichiometric experiments, the data support a mechanism involving an Au(I)/Au(III) redox cycle in which sequential electrophilic aromatic substitution of the arylsilane and the arene by Au(III) precedes product-forming reductive elimination and subsequent cycle-closing reoxidation of the metal. Despite the fundamental mechanistic similarities between the two auration events, high selectivity is observed for heterocoupling (C鈥揝i then C鈥揌 auration) over homocoupling of either the arylsilane or the arene (C鈥揝i then C鈥揝i, or C鈥揌 then C鈥揌 auration); this chemoselectivity originates from differences in the product-determining elementary steps of each electrophilic substitution. The turnover-limiting step of the reaction involves associative substitution en route to an arene 蟺-complex. The ramifications of this insight for implementation of the methodology are discussed.