Investigating the Nature of Palladium Chain-Walking in the Enantioselective Redox-Relay Heck Reaction of Alkenyl Alcohols

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• 作者：Margaret J. Hilton ; Li-Ping Xu ; Per-Ola Norrby ; Yun-Dong Wu ; Olaf Wiest ; Matthew S. Sigman
• 刊名：Journal of Organic Chemistry
• 出版年：2014
• 出版时间：December 19, 2014
• 年：2014
• 卷：79
• 期：24
• 页码：11841-11850
• 全文大小：554K
• ISSN：1520-6904

文摘

The mechanism of the redox-relay Heck reaction was investigated using deuterium-labeled substrates. Results support a pathway through a low energy palladium鈥揳lkyl intermediate that immediately precedes product formation, ruling out a tautomerization mechanism. DFT calculations of the relevant transition structures at the M06/LAN2DZ+f/6-31+G* level of theory show that the former pathway is favored by 5.8 kcal/mol. Palladium chain-walking toward the alcohol, following successive 尾-hydride eliminations and migratory insertions, is also supported in this study. The stereochemistry of deuterium labels is determined, lending support that the catalyst remains bound to the substrate during the relay process and that both cis- and trans-alkenes form from 尾-hydride elimination.