6-Aminouracils as precursors for the syntheses of fused di- and tricyclic pyrimidines

The treatment of 1-benzyl-, or 1-methyl-6-chlorouracil (1a,b) with nucleophilic primary amines followed by nitrosation, reduction, formylation and dehydro-cyclisation lead to xanthines 5 and 7. While, the treatment of uracil 8 with aromatic aldehydes 9a-f leads to the formation of dipyrimidinopyridines 10a-f, reaction with formalin and primary amines gives pyrimidopyrimidines 11a-d via double Michael reactions.