Influence of Positive Charge on the NMR Parameters of Mono- and Diprotonated Forms of 4-Dimethylaminopyridine

By the example of 4-dimethylaminopyridine and some of its derivatives taken as model nitrogen heterocycles with several basic centers, the correlation of the parameters of the NMR spectra with the direction (regioselectivity) and multiplicity of protonation of these compounds in CF 3 COOH–CD 2 Cl 2 , TfOH–CD 2 Cl 2 , and FSO 3 H–SbF 5 acid systems was studied. The established dependence of the spectral characteristics on the value of the introduced positive charge will be useful in studying the reactivity of similar heterocyclic systems in the presence of acidic agents.