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Switchable photocatalysis for the chemodivergent benzylation of 4-cyanopyridines.

Eleni GeorgiouDavide SpinnatoKang ChenPaolo MelchiorreKilian Muñiz
Published in: Chemical science (2022)
We report a photocatalytic strategy for the chemodivergent radical benzylation of 4-cyanopyridines. The chemistry uses a single photoredox catalyst to generate benzyl radicals upon N-F bond activation of 2-alkyl N -fluorobenzamides. The judicious choice of different photocatalyst quenchers allowed us to select at will between mechanistically divergent processes. The two reaction manifolds, an ipso -substitution path proceeding via radical coupling and a Minisci-type addition, enabled selective access to regioisomeric C4 or C2 benzylated pyridines, respectively. Mechanistic investigations shed light on the origin of the chemoselectivity switch.
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