Conclusions We conclude that the simple a-keto acids (pyruvic and phenylglyoxylic) are as useful as their esters for the preparation of pyrimido[4,5-c]pyridazine-4,5(1H,6W- diones from 6-(1-alkylhydrazino)isocytosines (1). Phenyl- and (phydroxypheny1)pyruvic acids cyclize with 1 in re- fluxing water to give 5-aryl-7-alkylpyrrolo[2,3-d]pyrimi- dines in modest, but synthetically useful, yields. However, alkylation of the hydrazino substituent of 1 appears to be ...