Hydrocarbation of C≡C bonds: quantification of the nucleophilic reactivity of ynamides.
Donor-substituted diarylcarbenium ions Ar2 CH(+) react with ynamides to give 1-amido-substituted allyl cations (α,β-unsaturated iminium ions). Kinetic studies show that these adducts, which correspond to the addition of a CH bond across the CC bond, are formed stepwise with initial formation of keteniminium ions and subsequent 1,3-hydride shifts. The linear correlations between the second-order rate constants (lg k2 , 20 °C) with the electrophilicity parameters E of the diarylcarbenium ions allow us to include ynamides in our comprehensive nucleophilicity scale and thus predict potential electrophilic reaction partners.
Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13 (Haus F), 81377 München (Germany) http://www.cup.uni-muenchen.de/oc/mayr/
Hans A
HA
Laub
Gwilherm
G
Evano
Herbert
H
Mayr
iminium ions; kinetic isotope effects; kinetics; linear free energy relationships; vinyl cations