1.2.4- Triazine-3,5-diones

Triazine-3,5-dione, 6-bromo-debromination, 3, 416 nucleophilic reactions, 3, 417... 

Triazine-3,5-dione, 6-mercapto-metal complexes, 3, 456 oxidation, 3, 411... 

A number of 1,2,4-triazines are of interest owing to their biological activity. 1,2,4-Triazine-3,5-diones (6) represent aza analogues of pyrimidine nucleic acid bases, a number of natural antibiotics are derivatives of pyrimido[5,4-e][l,2,4]triazine (7), and 4-amino-6-r-butyl-3-methylthio-l,2,4-triazin-5-one (8) and 4-amino-3-methyl-6-phenyl-l,2,4-triazin-5-one (9) are used as herbicides. 

Further compounds for which X-ray crystallographic analyses have been published are 5[2-(dimethylamino)propenyl]-6-methyl-3-phenyl-1,2,4-triazine (11) (73LA1970), 1,2,4-triazine-3,5-dione (6-azauracil 12) (74AX(B)1430>, 6-methyl-l,2,4-triazine-3,5-dione (6-azathymidine 13) (75AX(B)2519>, 2-0S-D-ribofuranosyl)-l,2,4-triazine-3.5-dione... 

Triazine-3,5-diones (33) show two N—H stretching vibrations at 3378 and 3374 cm-1 which were assigned to H-4 and H-2 according to comparisons with the 2- and 4-methyl derivatives. Also two bands in the carbonyl region were observed with 1,2,4-triazine-3,5-diones at 1730 and 1700 cm-1. The first band is shifted to 1723-1720 cm-1 if N-2 is alkylated, while the second band is shifted to 1687-1680 cm-1 when N-4 is alkylated. IR spectroscopy can therefore be used to determine the position of substituents in 1,2,4-triazine-3,5-diones (61CCC1680). 

A halogen directly attached to the 1,2,4-triazine ring is very reactive and can be replaced by most other nucleophiles as outlined in Scheme 9. Tlie reactivity toward neutral nucleophiles decreases from the 5-position to the 3- and 6-positions, while that towards anionic nucleophiles decreases from the 5-position to the 6- and 3-positions. Among nucleophiles which displace halogen atoms are water, alcohols, amines, hydrazine, hydroxyl-amine, thiols and hydrogen sulfide. It is also reported that the bromine in 6-bromo-1,2,4-triazine-3,5-dione can be replaced by fluorine (323) or by a cyano group (324). 

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