Hydrolysis of the amino groups in condensed 2, 4-diaminopyrimidine systems (1) has been used as a common method for the synthesis of oxo-substituted pyrimidines. In particular, the treatment with 6 M HCl usually yields exclusively the 2-amino-4-oxopyrimidine isomer (2). During our work, we found that the hydrolysis of the amino groups present in some condensed 2, 4-diaminopyrimidine systems unexpectedly afforded exclusively the 4- ...
