Electrolyte Enhanced Regioselectivity in the Electrophotocatalytic N ‐Arylation of Pyrazoles

Electrophotocatalysis (EPC), which combines photochemical and electrochemical activation, provides an alternative strategy for direct C–N bond formation under mild conditions. In this study, the regioselectivity of electrophotocatalytic C–H/N–H coupling of mesitylene with 3‐substituted pyrazoles was investigated in continuous flow using trisaminocyclopropenium (TAC) as the electrophotocatalyst. Supporting electrolyte screening identified Zn(BF ₄ ) ₂ ·6H ₂ O as the most effective additive, providing the corresponding N ‐arylated regioisomers in 91% combined yield with an improved N1:N2 ratio of 8:1 and reduced side‐product formation. Application to other 3‐substituted pyrazoles showed that the zinc electrolyte generally enhanced yield and regioselectivity, reaching yields up to 93% and N1:N2 ratios up to 100:1 for compatible substrates. These findings demonstrate that supporting‐electrolyte identity can modulate both reaction efficiency and N ‐regioselectivity in continuous‐flow electrophotocatalysis.