Direct β‑Functionalization of Cyclic Ketones with Aryl Ketones via the Merger of Photoredox and Organocatalysis

The direct β-coupling of cyclic
ketones with aryl ketones
has been achieved via the synergistic combination of photoredox catalysis
and organocatalysis. Diaryl oxymethyl or aryl–alkyl oxymethyl
radicals, transiently generated via single-electron reduction of ketone
precursors, readily merge with β-enaminyl radical species, generated
by photon-induced enamine oxidation, to produce γ-hydroxyketone
adducts. Experimental evidence indicates that two discrete reaction
pathways can be operable in this process depending upon the nature
of the ketyl radical precursor and the photocatalyst.