Amine‐Free, Directing‐Group‐Free and Redox‐Neutral α‐Alkylation of Saturated Cyclic Ketones

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. 1H 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. As a powerful complement to existing organic amine catalysis, direct activation of the α‐C−H bonds of saturated cyclic ketones is realized for the first time in an amine‐free and directing‐group‐free catalytic mode. The carbonyl group binds to a defect site of the quantum dot (QD) surface, selectively weakening the α‐C−H bond, instead of the β‐C−H bond, and exclusively generating an α‐C radical under visible‐light irradiation. This unique activation platform leads to selective activation of the α‐C−H bonds of cyclic ketones under redox‐neutral conditions.