SCHEDULED MAINTENANCE
Switchable photocatalysis for the chemodivergent benzylation of 4-cyanopyridines†
Davide
Spinnato, 
‡ab
Paolo
Melchiorre
*ac
and
‡ab
Paolo
Melchiorre
*ac
and
Abstract
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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