Oxazolo[3,2-a]pyridinium and oxazolo[3,2-a]pyrimidinium salts in organic synthesis (original) (raw)

The methods for the synthesis of oxazolo[3,2 a]pyridinium and oxazolo[3,2 a]pyrimidinium salts and their reactivities are reviewed. Both systems exhibit ambident properties in reactions with nucleophiles; depending on the substituents and the reagents, both the oxazole and azine rings can undergo opening and transformations. A number of new methodologies involving oxazolopyridini um and oxazolopyrimidinium salts for the design of functionalized oxazoles, imidazoles, fused pyrroles, and other heterocyclic systems are generalized.