Abstract The synthesis of 6‐dimethylaminomethylenaminopyrimidin‐4(3 H )‐ones 2 and its reaction with β‐dimethyl‐aminopropiophenone hydrochloride 3 is discussed in this work. The reaction of 6‐aminopyrimidin‐4(3 H )‐ones 1 with an excess of dimethylformamide dimethyl acetal gives rise to the formation of 6‐dimethylaminomethyleneaminopyrimidines 2. The heating of equimolecular quantities of 2 and 3 in dimethylformamide leads to the 6‐aroylpyrido[2,3‐ d ]pyrimidines derivatives 4. The structures of compounds 2 and 4 were determined on the basis of nmr measurements.