Study on Oxazolopyrimidines. VI. Formation of 3-Substituted Xanthines via 7(6H)-Iminooxazolopyrimidines

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Abstract
The condensation of several primary amines with 4-cyano-5-dialkoxymethylenaminooxazole gave 6-substituted 5-alkoxy-7(6H)-immooxazolo[5,4-d]pyrimidines. These compounds were converted into 3-substituted xanthines by treatment with aqueous alkali or by heating in formamide. The present reaction was compared with an analogous reaction, formation of 9-substituted hypoxantines via 7-aminooxazolo[5,4-d]pyridimine derivatives, and the difference in the reaction course was discussed in terms of the effect of substituents on the stability of oxazolopyrimidine intermediates.