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

The activation of the alpha-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 alpha-C-H bond activation of ketone, directing groups are also required to control the reaction selectivity. Reported herein is the first alpha-alkylation of cyclic ketones in the absence of an amine catalyst and directing group. H-1 NMR, XPS, EPR studies and DFT calculations indicate that an alpha-carbon radical intermediate is formed through direct and selective activation of the inert alpha-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 alpha-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 alpha-C-H functionalization of ketones in carbonyl chemistry.