Alternative Protonation Centres in the Molecule of 1-(N-Methylimino)-2-(N,N-disubstituted)aminobut-2-ene

The formation of enammonium salts by protonation of azomethine derivatives of N,N-disubstituted α-aminocrotonaldehydes, their easy E,Z-isomerisation and subsequent transformation to the corresponding immonium salts has been found for the first time.