The direct α-arylation of unactivated carbonyl compounds using aryl halides represents a powerful method to synthesize criti-cal building blocks for diverse useful compounds. Numerous synthetic methods exist to forge C(sp2)-C(sp3) bonds, albeit metal free direct α-arylation of unactivated cyclic ketones has long been an elusive transformation. Herein, we report a green-light-mediated α-arylation of unactivated ketones from readily available aryl halides via activation of a C(sp2)-X bond (X=I, Br, Cl) and an α-carbonyl C(sp3)-H bond in a single photocatalytic cycle. This approach is characterized by its mild reaction conditions, operational simplicity, and wide functional group tolerance. Importantly, the impressive outcome from multi-gram photocatalytic reaction underpins the strength of this method as a potentially practical and attractive approach for scale-up industrial purposes. The utility and scope of this reaction were further demonstrated by new syntheses of several feedstock chemicals that are commercially expensive but critical for synthesizing numerous pharmaceutical agents.
Additional mechanistic experiments have been performed, including Transient Absorption spectroscopy and spectro electrochemical measurements, to support the involvement of PET mechanism via the formation of a radical dication acridinium.
Supportive Information - Photoredox α-Arylation of Carbonyl Compounds