Introducing strong acids: The reaction of electron‐rich arenes with Tf2CHCH2CHTf2 (Tf=trifluoromethanesulfonyl; triflyl) smoothly gave 2,2‐bis(triflyl)ethylated arenes. This reaction provides a convenient methodology for the introduction of a Tf2CH group, which is known to be a strongly Brønsted acidicfunctionality, to organic compounds in a regioselective manner (see scheme). On the basis of this