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Lakhdar, Sami; Mayr, Herbert (2011): Counterion effects in iminium-activated electrophilic aromatic substitutions of pyrroles. In: Chemical Communications, Vol. 47, No. 6: pp. 1866-1868


Electrophilic substitution of pyrroles by a,b-unsaturated iminium ions is slow in acetonitrile when only weakly basic counterions are present. When the reactions are carried out in the presence of KCF3CO2, fast deprotonation of the intermediate r-adducts occurs, and the rate constant for the rate-determining CC bond-forming step can be predicted from the electrophilicity parameter E of the iminium ion and the N and s parameters of the pyrroles.