A diversity oriented, microwave assisted synthesis of N-substituted 2-hydro-4-amino-pyrido[2,3-d]pyrimidin-7(8H)-ones

A protocol for the synthesis of N-substituted 2-hydro-4-amino-pyrido[2,3-d] pyrimidin-7(8H)-ones (11) is described. Thus, the formylation of a 2-aminopyridone 12 in 85% formic acid/Ac₂O, proceeding via in situ cyclization to the intermediate formamide 13, affords the corresponding 2-hydro-4-oxo-pyridopyrimidine 14, which is converted to a 4-chloro- pyridopyrimidine 15 upon treatment with POCl₃. The subsequent transformation to the title compounds is carried by treatment with the corresponding amine in MeOH under microwave irradiation conditions.