Kinetic Resolution of Racemic Radicals in Asymmetric Photoredox Minisci Reactions with Azaarenes for Precise Construction of Two Non-adjacent Stereocenters.

Despite the significant potential of photocatalysis as a robust synthetic tool, the high reactivity of radicals often presents challenges in achieving optimal chemoselectivity. In this study, we demonstrate that this inherent limitation can be strategically harnessed for asymmetric photoredox catalysis. By utilizing a chiral catalyst to facilitate kinetic resolution between the two enantiomers of racemic radical intermediates, one enantiomer selectively undergoes the desired transformation, while noncatalytic side reactions deplete the other enantiomer.

Metal-Free Hydropyridylation of Thioester-Activated Alkenes via Electroreductive Radical Coupling.

An electrochemical hydropyridylation of thioester-activated alkenes with 4-cyanopyridines has been developed. The reactions experience a tandem electroreduction of both substrates on the cathode surface, protonation, and radical cross-coupling process, resulting in a variety of valuable pyridine variants, which contain a tertiary and even a quaternary carbon at the α-position of pyridines, in high yields. The employment of thioesters to the conjugated alkenes enables no requirement of catalyst and high temperature, representing a highly sustainable synthetic method.