Palladium Pincer Complex-Catalyzed Trimethyltin Substitution of Functionalized Propargylic Substrates. An Efficient Route to Propargyl- and Allenyl-Stannanes

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• 作者：Johan Kjellgren ; Henrik Sundé ; n ; and Ká ; lmá ; n J. Szab&oacute
• 刊名：Journal of the American Chemical Society
• 出版年：2004
• 出版时间：January 21, 2004
• 年：2004
• 卷：126
• 期：2
• 页码：474 - 475
• 全文大小：53K
• 年卷期：v.126,no.2(January 21, 2004)
• ISSN：1520-5126

文摘

Palladium pincer complex-catalyzed reaction of functionalized propargyl chloride (and mesylate) derivatives with hexamethylditin gives allenyl- and propargyl-stannane products. This catalytic activity is in sharp contrast with the reactivity of commonly used palladium(0) catalysts inducing addition of hexamethylditin to the triple bond. The product distribution of the pincer complex-catalyzed reaction is controlled by the substituent effects of the propargylic substrate: electron-withdrawing functionalities give mainly allenyl stannane products, while with electron-donating groups the main product is propargyl stannane. The catalytic reaction proceeds under very mild conditions tolerating many functionalities such as OH, OAc, NR₃, and NR₂Ac groups. Our mechanistic studies indicate that the key intermediate of the reaction is a monotrimethylstannane palladium pincer complex. A remarkable feature of the studied catalytic process is that the palladium catalyst does not undergo redox reactions, but its oxidation state is restricted to palladium(II). Since palladium(0) intermediates does not occur in this process, the catalyst is very stable and highly chemoselective.