Heterocyclic studies. Part XVIII. Some 6,7-diaminoimidazo[1,2-a]-pyrimidines and derived tricyclic compounds

Abstract

Reduction of the 7-(substituted amino)-2,3-dihydro-5-methyl-6-nitroimidazo[1,2-a]pyrimidines (I; X = NO₂, R = H, Me, Et, Ch₂Ph, or CH₂·CH₂·OH) gave the corresponding 6-amino-derivatives (I; X = NH₂). The same compounds were obtained by simultaneous reduction and cyclisation of 4-(substituted amino)-2-(2-chloroethylamino)-6-methyl-5-nitropyrimidines (II; R = H, Me, Et, CH₂Ph, or CH₂·CH₂·OH). Some of the diamines (I; X = NH₂) were treated with nitrous acid, thionyl chloride, urea, carbon disulphide, formic acid, oxalic acid, or biacetyl to give imidazo[1,2-a]triazolo[4,5-d]pyrimidines (IV; R¹= CH₂Ph or Et, R²= CHN·OH), imidazo-[1,2-a]isothiazolo[3,4-e]pyrimidines (V; R = CH₂Ph or Me), imidazo[1,2-a]purines [e.g.(VI; R¹= CH₂Ph or Me, R²= SH)] and imidazo[2,1-b]pteridines [(VIII) and (IX)]. Several of these reactions involved the 5-methyl group of the starting diamine (I; X = NH₂).