Thermocontrolled Radical Nucleophilicity vs Radicophilicity in Regiodivergent C–H Functionalization

The temperature-dependent switching behavior of the saccharin
radical
is demonstrated, enabling the regiodivergent C3–H
and C7–H functionalization of quinoxalin-2(1H)-ones. The saccharin radical was generated through N–Br
bond cleavage in N-bromosaccharin (NBSA) and was
observed to transition between radical and radicophile roles. At −10
°C, it was utilized as a radicophile, resulting in 100% C3-amination, while at +35 °C, it acted as a radical, leading
to exclusive C7-bromination. Radical nucleophilicity was
controlled by temperature modulation.