Switchable photocatalysis for the chemodivergent benzylation of 4-cyanopyridines

Identifier:  imarina:9267367

Handle: https://hdl.handle.net/20.500.11797/imarina9267367

Authors:  Georgiou E; Spinnato D; Chen K; Melchiorre P

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.