Lakhdar, Sami; Mayr, Herbert
Counterion effects in iminium-activated electrophilic aromatic substitutions of pyrroles.
In: Chemical Communications, Vol. 47, Nr. 6: S. 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.