Quinolizinium and Related Systems

Practically all the reactions of quinolizinium ions are similar to those of pyridinium salts, thus they are resistant to electrophilic attack, but readily undergo nucleophilic addition, the initial adducts undergoing spontaneous electrocyclic ring opening to afford, finally, 2-substituted pyridines however the susceptibility of the cations to nucleophiles is not extreme - Uke simpler pyridinium salts they are stable to boiling water. 

Quinolizine derivatives are usually prepared by cyclisations onto the nitrogen in a precursor pyridine. Quinazolones can be made to undergo electrophilic substitution, at C-l/C-3, there being a clear analogy with the reactivity of pyridones. 

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