New Polycyclic Diamine Scaffolds from Dimerization of 3-Alkyl-1,4-dihydropyridines in Acidic Medium

3-Alkyl-1,4-dihydropyridines dimerize in acidic medium, at
low temperature, to give polycyclic imminium salts derivatives that were reduced to afford new polycyclic diamine
scaffolds. The reaction can be extended to enantiopure series
starting from R-(+)- or S-(−)-1-phenylethylamine. Long
exposure of the polycyclic imminium salt intermediates to
air moisture at 20 °C resulted in formation of new amide
derivatives. This is probably due to the addition of water
followed by an intramolecular oxido-reduction process.