美国斯克利普斯研究所Jin-Quan Yu团队报道了通过C–H活化实现配体控制羧酸的发散脱氢反应。相关研究成果于2021年11月11日发表于国际顶尖学术期刊《科学》。

通过亚甲基C–H活化将烷基链脱氢转化为烯烃仍然是一个重大挑战。

研究人员报道了两类吡啶-吡啶酮配体，通过钯催化的羧酸的β-亚甲基C–H活化实现不同的脱氢反应，从而直接合成α，β-不饱和羧酸或γ-亚烷基丁烯内酯。该反应的定向性质允许羧酸在存在其他烯化功能（如酮）的情况下进行化学选择性脱氢，提供现有羰基脱饱和协议无法实现的化学选择性。通过配体促进的C（sp3）–H键优先激活C（sp2）–H键或串联脱氢或乙烯基C–H炔基化序列克服产物抑制。脱氢反应与分子氧作为末端氧化剂相容。

附：英文原文

Title: Ligand-controlled divergent dehydrogenative reactions of carboxylic acids via C–H activation

Author: Zhen Wang, Liang Hu, Nikita Chekshin, Zhe Zhuang, Shaoqun Qian, Jennifer X. Qiao, Jin-Quan Yu

Issue&Volume: 2021-11-11

Abstract: Dehydrogenative transformations of alkyl chains to alkenes through methylene C–H activation remain a substantial challenge. We report two classes of pyridine-pyridone ligands that enable divergent dehydrogenation reactions through Pd-catalyzed β-methylene C–H activation of carboxylic acids, leading to the direct syntheses of α,β-unsaturated carboxylic acids or γ-alkylidene butenolides. The directed nature of this pair of reactions allows chemoselective dehydrogenation of carboxylic acids in the presence of other enolizable functionalities such as ketones, providing chemoselectivity that is inaccessible with existing carbonyl desaturation protocols. Product inhibition is overcome through ligand-promoted preferential activation of C(sp3)–H bonds over C(sp2)–H bonds or a tandem dehydrogenation or vinyl C–H alkynylation sequence. The dehydrogenation reaction is compatible with molecular oxygen as the terminal oxidant.

DOI: abl3939

Source: https://www.science.org/doi/10.1126/science.abl3939