3- Methoxy-1,2,4-triazine 1 -oxides halogenation

The presence of an TV-oxide group activates the 1,2,4-triazine ring toward electrophilic attack, for instance, in halogenation reactions. Thus, 3-methoxy- and 3-amino(alkylamino)-1,2,4-triazine 1-oxides 16 react easily with chlorine or bromine to form the corresponding 6-halo-1,2,4-triazine 1-oxides 17 (77JOC3498, 78JOC2514). 

The halogenation of 3-methoxy- or 3-methyl(dimethyl)amino-1,2,4-triazine 2-oxides 18 was found to proceed in a similar manner, resulting in 6-halo-1,2,4-triazine 2-oxides 19 (77JOC3498, 78JOC2514). 

---