Key Laboratory of Photochemical Conversion and Optoelectronic Materials, New Cornerstone Science Laboratory, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
School of Future Technology, University of Chinese Academy of Sciences, Beijing, 100049, China.
Angew Chem Int Ed Engl. 2023 Jul 17;62(29):e202305679. doi: 10.1002/anie.202305679. Epub 2023 Jun 12.
The activation of the α-C-H bond of ketones typically requires an amine and a directing group to guide the reaction selectivity in amine-catalysis carbonyl chemistry. For an α-C-H bond activation of ketone, directing groups are also required to control the reaction selectivity. Reported herein is the first α-alkylation of cyclic ketones in the absence of an amine catalyst and directing group. H NMR, XPS, EPR studies and DFT calculations indicate that an α-carbon radical intermediate is formed through direct and selective activation of the inert α-C-H bond of ketones chelating on the surface of colloidal quantum dots (QDs). Such an interaction is essential for weakening the C-H bond, as exemplified, using CdSe QDs as the sole photocatalyst to execute α-C-H alkylation of cyclic ketones under visible-light irradiation. Without an amine catalyst and directing group, the high step- and atom-economy transformation under redox-neutral condition opens a new way for α-C-H functionalization of ketones in carbonyl chemistry.
酮的α-C-H 键的活化通常需要胺和导向基团来引导胺催化羰基化学中的反应选择性。对于酮的α-C-H 键活化，也需要导向基团来控制反应选择性。本文报道了在没有胺催化剂和导向基团的情况下，环状酮的首次α-烷基化反应。1 H NMR、XPS、EPR 研究和 DFT 计算表明，通过表面胶体量子点（QD）螯合的酮的惰性α-C-H 键的直接和选择性活化，形成α-碳自由基中间体。这种相互作用对于削弱 C-H 键是必不可少的，例如，使用 CdSe QD 作为唯一的光催化剂，在可见光照射下执行环状酮的α-C-H 烷基化反应。在没有胺催化剂和导向基团的情况下，在氧化还原中性条件下的高步骤和原子经济性转化为羰基化学中酮的α-C-H 官能化开辟了一条新途径。
