A Tf2O-triggered dearomative triazinylmethylation of isoquinolines and other azaarenes utilizing acetonitrile as the nucleophile has been developed through a formal five-component reaction. This method showcases a broad substrate scope and exceptional functional group compatibility, presenting a mild and expedient synthetic approach. Kinetic studies, including kinetic isotope effect (KIE) and Hammett analysis, indicate that the activation of isoquinolines by Tf2O constitutes the rate-limiting step.