The Vilsmeier adduct (11) proved to be a versatile intermediate for the preparation of heterocycles substituted with a pyrazine ring. Thus, condensation with the carbonyl reagents hydroxylamine and phenylhydrazine furnished the isoxaaole (IVa) and pyrazole (IVb), respectively. Similarly, reaction with urea derivatives or amidines gave the 5-(2-pyraainyl)- pyrimidines (Va-c).
