STERICALLY CROWDED HETEROCYCLES .1. MOLECULAR-STRUCTURE OF 3-CHAIN SUBSTITUTED 2-PHENYLIMIDAZO[1,2-A]PYRIDINIUM SALTS

-1,3-diphenyl-3-oxopropenyl]imidazo[1,2-a]pyridine (I) was converted t o corresponding ,3-diphenyl-3-oxopropenyl]imidazo[1,2-a]pyridinium sal ts III - VI and ,3-diphenyl-3-oxopropenyl]imidazo[1,2-a]pyridinium per chlorate (VIT). The protonation site is discussed in terms of calculat ed molecular energies of alternative cations. The X-ray structure anal yses of enone I and its quaternary periodide III are reported and comp ared with the PM3 molecular optimizations,H-1 NMR and C-13 NMR spectra reveal well changes of molecular structures caused by the transformat ion of the base I into salts III - VII.