6-Methyl- 1,2,4-triazine-3-(2H)-selenone-5(4H)-one(l) reacts in the presence of
base with phenacyl bromide to give a mixture of compounds (2) and (3). This mixture is dehydrated in the presence of H,SO, to give 3-phenyl-6 methyl-7H-selenazolo[3,2-b] [I ,2,4] triazin-7-one (6). For careful structure assignment of (6) its regioisomer 3-methyl-6-phenyl-4H-selenazolo [2,3-c] [ 1,2,4] triazin-4-one (8) was unambiguously synthesized and its spectroscopic data were Compared with those of (6)