13C-NMR spectra of substituted 1,4-dihydropyridines

It has been found that the electron shift in the C(2)=C(3) bond, under the influence of the substituent attached to the nitrogen atom and the substituents in the 3- and 5-positions, occurs via a π-inductive mechanism. 4-(1,4-Dihydropyridyl) functional groups behave as electron donating substituents via an inductive mechanism.