Clarification of the ring-closure of certain 4,5-diaminopyrimidines to 6-substituted 8-alkylpurines

Abstract

Acylation of 5,6-diaminopyrimidin-4(3H)-one (I) furnished the bisacylamino-derivatives (IIa–d). Contrary to previous reports, treatment of these diamides (IIa–d) with refluxing aqueous base did not furnish 8-alkylpurines, but the monoacylaminopyrimidinone derivatives (IIIa–d). The monoacylamino-derivatives (IIIa–d) are conveniently ring-closed to 8-alkyl-6-chloro-9H-purines with phosphoryl chloride. Acylation of 4,5,6-triamino-pyrimidine (VI) gave monoacylamino-derivatives (VIIa and b) which underwent ready ring-closure to 8-alkyl-9H-adenines (VIIIa and b) in aqueous alkali.