Allene C(sp2)–H Activation and Alkenylation Catalyzed by Palladium,Journal of the American Chemical Society

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Allene C(sp2)–H Activation and Alkenylation Catalyzed by Palladium
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2021-12-16 , DOI: 10.1021/jacs.1c11528
Benedikt S Schreib ₁ , Mina Son ₂ , Françoise A Aouane ₁ , Mu-Hyun Baik ₂ , Erick M Carreira ₁

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The selective transition-metal-mediated activation of C(sp²)–H bonds of allenes is a formidable challenge because of the competitive, intrinsic reactivity of cumulated double bonds. Herein, we report a Pd-catalyzed C–H alkenylation of electronically unbiased allenes, affording penta-1,2,4-triene products in up to 94% yield. A picolinamide directing group enables the formation of putative allenyl-palladacycles, which subsequently participate in a turnover-limiting Heck-type reaction with electron-deficient alkene coupling partners. This mechanistic proposal is consistent with experimental and computational investigations. Additionally, we report for the first time the use of picolinamide N,O-acetals as readily removable auxiliaries for C–H activation reactions, allowing the efficient alkenylation of allenyl carbinol derivatives. Successful removal of the directing groups without affecting the reactive penta-1,2,4-triene substructure of the products is demonstrated.

中文翻译：

钯催化的丙二烯C(sp2)-H活化和烯基化

由于累积双键的竞争性、内在反应性，丙二烯的 C(sp ² )-H 键的选择性过渡金属介导的活化是一项艰巨的挑战。在此，我们报道了电子无偏丙二烯的 Pd 催化 C-H 烯基化，以高达 94% 的产率提供五-1,2,4-三烯产物。吡啶酰胺导向基团能够形成假定的烯基-钯环，其随后与缺电子烯烃偶联伙伴参与限制周转的 Heck 型反应。这种机制提议与实验和计算研究一致。此外，我们首次报道了使用吡啶酰胺 N , O-缩醛作为 C-H 活化反应的易于去除的助剂，可以有效地进行烯基甲醇衍生物的烯基化。证明了在不影响产物的反应性五-1,2,4-三烯亚结构的情况下成功去除导向基团。

更新日期：2021-12-29

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