Relayed Proton Brake in N‑Pyridyl-2-iso-propylaniline Derivative: Two Brakes with One Proton

The addition of methanesulfonic acid to N-(2,6-dimethylpyridin-4-yl)-N-methyl-2-iso-propylaniline led to the selective protonation of the pyridine nitrogen atom, resulting in a significant deceleration of the rotation rates around both N-pyridyl and N-(i-Pr)­phenyl bonds through a relayed brake mechanism.