Abstract The reaction of 2,3,6‐triaminopyridine 1 and 4,5,6‐triaminopyrimidine 2 with one equivalent of the chal‐cones 3, in acetic acid, leads to the formation of the 8‐amino‐2,3‐dihydro‐1 H ‐pyrido[2,3‐ b ][1,4]diazepine and 6‐amino‐2,3‐dihydro‐1 H ‐pyrimido[4,5‐ b ][1,4]diazepine derivatives 4 and 5 . The products were characterized by NMR techniques such as 13 C, 1 H, and DEPT including selective 13 C{ 1 H} decoupling experiments.