1‐(4,6‐Diethoxy­pyrimidin‐2‐yl)‐2‐thioxo‐2,3‐dihydro­pyrido[2,3‐d]pyrimidin‐4(1H)‐one

In the title compound, C₁₅H₁₅N₅O₃S, two parallel inter­molecular N—H?S hydrogen bonds, forming an eight‐membered ring, link two mol­ecules into a dimer unit; these dimer units linked into a chain of edge‐fused rings by weak C—H?O hydrogen bonds.