Reaction of 6-aminouracils with excess nitrosating agent

Abstract

Relatively high thermal stability in combination with the lack of color characteristic of nitrosouracils suggests that dinitroso derivatives III are stabilized in the form of cyclic azo N, N `-dioxide. Another evidence of the cyclic structure is isolation of 4-methyl4,5,6,7-tetrahydro-3H-[1,2,3]triazolo[4,5-d]pyrimidine-5,7-dione IV [5] upon reduction of IIIa with hydrogen over 2% Pd/C. On the other hand, when heated in water in the presence of acids, compounds IIIa and IIIb enter into the Fischer3Hepp reaction similar to arylnitrosamines [6]. Heating of an equimolar mixture of 6-amino-1-methyluracil Ib and its dinitroso derivative IIIa in the presence of aqueous acetic acid affords 6-amino-1-methyl-5-nitrosouracil IIb in 80% yield.