Reactions of halogenoquinolizinium bromides with diethylamine

The reactions of quinolizinium bromide (QB) and its four monobromo derivatives with diethylamine have been investigated. For Br in position 2 or 4, substitution is the main process, whereas for Br in positions 1 and 3 quantitative ring opening is found. The substituted pyridylbutadienes formed by ring opening, are cis-trans-butadienes, which isomerize into the all-trans forms. The steric cours of the ring opening is explained.