Synthetic and mechanistic studies of Pd-catalyzed C-H arylation with diaryliodonium salts: evidence for a bimetallic high oxidation state Pd intermediate.
Synthetic and mechanistic studies of Pd-catalyzed C-H arylation with diaryliodonium salts: evidence for a bimetallic high oxidation state Pd intermediate.
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DOI：
10.1021/ja904116k
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发表时间：
2009-08-12
影响因子：
15
通讯作者：
Sanford, Melanie S.
中科院分区：
文献类型：
--
作者：
Deprez, Nicholas R.;Sanford, Melanie S.
本文介绍了钯催化二芳基碘鎓盐配体定向C-H芳化反应的底物范围和反应机理。这种转化被应用于合成各种不同的联芳基产品，使用导向基团包括吡啶、喹啉、吡咯烷酮和恶唑烷酮。利用一般结构[Mes-I-Ar]BF4的碘（III）试剂，高收率地转移了电子和立体不同的芳基（Ar）。机理研究建立了各组分催化反应的动力学顺序，确定了催化剂和碘（III）试剂的静息状态，量化了芳化试剂对反应速率的电子影响，建立了分子内和分子间的1ºH/D动力学同位素效应。在这些研究的基础上，这种转化被提议通过[Mes-I-Ph]BF4对Pd二聚体[Pd(N ~ C)(OAc)]2 （N ~ C = 3-甲基-2-苯基吡啶）进行限制氧化来进行。该机制暗示双金属高氧化态钯作为关键的催化中间体。详细讨论了该机制的意义和其他方面的建议。
This paper describes the substrate scope and mechanism of Pd-catalyzed ligand-directed C–H arylation with diaryliodonium salts. This transformation was applied to the synthesis of a variety of different biaryl products, using directing groups including pyridines, quinolines, pyrrolidinones, and oxazolidinones. Electronically and sterically diverse aryl groups (Ar) were transferred in high yield using iodine(III) reagents of general structure [Mes–I–Ar]BF4. Mechanistic investigations have been conducted that establish the kinetic order of the catalytic reaction in each component, determine the resting state of the catalyst and the iodine(III) reagent, quantify the electronic influence of the arylating reagent on the reaction rate, and establish the intra- and intermolecular 1º H/D kinetic isotope effect. On the basis of these studies, this transformation is proposed to proceed via turnover limiting oxidation of the Pd dimer [Pd(N∼C)(OAc)]2 (N∼C = 3-methyl-2-phenylpyridine) by [Mes–I–Ph]BF4. This mechanism implicates a bimetallic high oxidation state Pd species as a key catalytic intermediate. The significance of this and other aspects of the proposed mechanism are discussed in detail.
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