Synthesis and properties of 3-thiono derivatives of pyrido[2,3-e]-asym-triazine

2-Amino-3-hydrazinopyridine reacts with carbon disulfide to give 1,2,3,4-tetrahydropyrido2,3-e]-asym-triazine-3-thione. The methylthio derivative obtained from it is oxidized to the sulfone, which undergoes exchange of the methylsulfonyl group for an amine residue in the cold. The methylthio derivative undergoes this sort of reaction only on heating, whereas in the cold it reacts with amines to give adducts that are unstable in solution and on heating.