Chemoselective Catalytic α-Oxidation of Carboxylic Acids: Iron/Alkali Metal Cooperative Redox Active Catalysis
Chemoselective Catalytic α-Oxidation of Carboxylic Acids: Iron/Alkali Metal Cooperative Redox Active Catalysis
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DOI：
10.1021/jacs.0c00727
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发表时间：
2020-03-04
影响因子：
15
通讯作者：
Ohshima, Takashi
中科院分区：
文献类型：
--
作者：
Tanaka, Tsukushi;Yazaki, Ryo;Ohshima, Takashi
我们开发了一种化学选择性催化活化羧酸的1 e（-）自由基过程。在自由基条件下优先进行不希望的脱羧的各种羧酸的α-氧化在优化的条件下有效地进行。甚至在更酸性的羰基存在下也实现了羧酸的化学选择性烯醇化。广泛的机理研究表明，铁物种和碱金属离子衍生的4埃分子筛的协同作用，大大促进烯醇化。首次实现了未保护羧酸的催化烯醇化，而无需外部添加化学计量量的布朗斯台德碱。所形成的氧化还原活性杂环己烯二醇盐有效地与自由基克里思偶联，提供合成有用的α-羟基和酮酸衍生物。
We developed a chemoselective catalytic activation of carboxylic acid for a 1e(-) radical process. alpha-Oxidation of a variety of carboxylic acids, which preferentially undergo undesired decarboxylation under radical conditions, proceeded efficiently under the optimized conditions. Chemoselective enolization of carboxylic acid was also achieved even in the presence of more acidic carbonyls. Extensive mechanistic studies revealed that the cooperative actions of iron species and alkali metal ions derived from 4 angstrom molecular sieves substantially facilitated the enolization. For the first time, catalytic enolization of unprotected carboxylic acid was achieved without external addition of stoichiometric amounts of Bronsted base. The formed redox-active heterobimetallic enediolate efficiently coupled with free radical TEMPO, providing synthetically useful alpha-hydroxy and keto acid derivatives.