Novel Ring Contraction of 6-Azauracil Derivatives

Derivatives of 6-azauracil were lithiated at −100°C with and without an electrophilic agent. Reactions of appropriate 6-azauracils with t-butyllithium and lithium diisopropylamide gave, as a result of a ring contraction, compounds 5 and 6. The structure of compound 5 was undeniably established by X-ray analysis. A mechanism of the novel ring transformation of 1,2,4-triazines to imidazoles is discussed.