Wang Miao, Huang Yahao, Hu Peng
Institute of Green Chemistry and Molecular Engineering, Lehn Institute of Functional Materials, School of Chemistry, Sun Yat-sen University, Guangzhou 510275, China.
Science. 2024 Feb 2;383(6682):537-544. doi: 10.1126/science.adj9258. Epub 2024 Feb 1.
Hydrogen atom transfer (HAT) processes can overcome the strong bond dissociation energies (BDEs) of inert C(sp)-H bonds and thereby convert feedstock alkanes into value-added fine chemicals. Nevertheless, the high reactivity of HAT reagents, coupled with the small differences among various C(sp)-H bond strengths, renders site-selective transformations of straight-chain alkanes a great challenge. Here, we present a photocatalytic intermolecular radical sampling process for the iron-catalyzed borylation of terminal C(sp)-H bonds in substrates with small steric hindrance, including unbranched alkanes. Mechanistic investigations have revealed that the reaction proceeds through a reversible HAT process, followed by a selective borylation of carbon radicals. A boron-sulfoxide complex may contribute to the high terminal regioselectivity observed.
氢原子转移（HAT）过程能够克服惰性C(sp)-H键的强键解离能（BDE），从而将原料烷烃转化为高附加值的精细化学品。然而，HAT试剂的高反应活性，再加上各种C(sp)-H键强度之间的差异较小，使得直链烷烃的位点选择性转化成为一项巨大挑战。在此，我们展示了一种光催化分子间自由基采样过程，用于铁催化空间位阻较小的底物（包括直链烷烃）中末端C(sp)-H键的硼化反应。机理研究表明，该反应通过可逆的HAT过程进行，随后是碳自由基的选择性硼化反应。一种硼-亚砜配合物可能有助于观察到的高末端区域选择性。
