Synthesis of substituted 3‐(5‐amino‐[1,3,4]thiadiazol‐2‐yl)‐2 H ‐pyrano[2,3‐ c ]pyridin‐2‐ones

An efficient two‐step synthesis of novel 3‐(5‐amino‐[1,3,4]thiadiazol‐2‐yl)‐2 H ‐pyrano[2,3‐ c ]pyridine‐2‐ones was developed. In the first step, a new 2 H ‐pyrano[2,3‐ c ]pyridine‐3‐carboxamide 5 was prepared by Knoevenagel condensation of pyridoxal hydrochloride with cyanoacetamide. In the second step, the reaction of carboxamide 5 with a series of N 4 ‐substituted thiosemicarbazides yielded a library of 35 dis crete compounds 8 {1–35} in high yields. The intermolecular recyclization mechanism leading to these products is discussed.