Conformation of some 2,4,6-trisubstitued pyridinium salts

Favored conformations of some pyridinium salts could be accessed by NOE experiments and calculations. The favored conformation of 2,4,6-trimethylpyridinium salt 1 is a slightly distorted open conformation. For 2,4,6-trimethylpyridinium salts 2 and 3, favored distorted closed gauche conformations, that would be stabilized by a π-cation interaction, are proposed. Favored conformations for 2,4,6-triphenyl salts 4 and 5 are very similar to the analogous for 1 and 2 indicating little influence of the nature of 2,6-substituents of the heterocyclic ring.