Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
J Am Chem Soc. 2020 Aug 19;142(33):14064-14068. doi: 10.1021/jacs.0c06580. Epub 2020 Aug 7.
Carbon homologation reactions occur within the well-known Fischer-Tropsch process, usually mediated by transition metal catalysts at high temperature. Here we report the low-temperature, heavy-metal-free homologation of a carbon chain using CO as a C-source showing for the first time that transition-metal catalysts are not required for Fischer-Tropsch-type reactivity. Reaction of an alkylborane in the presence of either LiHBEt or LiAlH resulted in multiple CO insertion/reduction events to afford elongated chains by more than two methylene (-CH-) units, affording aldehyde products upon oxidative aqueous workup. Theoretical and experimental mechanistic studies indicate that the boron terminus is responsible for CO incorporation as well as sequential hydride delivery leading to reduction of acylborane intermediates to alkylboranes.
碳同系化反应发生在著名的费托工艺中，通常在高温下由过渡金属催化剂介导。在这里，我们报告了在低温、无重金属条件下使用 CO 作为 C 源对碳链进行同系化，首次表明费托型反应不需要过渡金属催化剂。在 LiHBEt 或 LiAlH 的存在下，烷基硼烷的反应导致多次 CO 插入/还原反应，通过两个以上的亚甲基（-CH2-）单元延伸链，在氧化的水性后处理中得到醛产物。理论和实验的机理研究表明，硼端负责 CO 的掺入以及顺序氢化物的传递，导致酰基硼中间体还原为烷基硼烷。
