Dj. Collins et al., Dihydro-1,2,4-triazin-6(1H)-ones. III - Oxidation products of 1-methyl-3-phenyl-4,5-dihydro-1,2,4-triazin-6(1H)-one, AUST J CHEM, 52(10), 1999, pp. 971-975
1-Methyl-3-phenyl-4,5-dihydro-1,2,4-triazin-6(1H)-one (1) undergoes aerial
oxidation to give a mixture of 1-methyl-3-phenyl-1,2,4-triazin-6(1H)-one (2
) and 1-methyl-3-phenyl-1,4-dihydro-1,2,4-triazine-5,6-dione (3). The dehyd
ro derivative (2) was cleanly prepared by the oxidation of (1) with 2,3-dic
hloro-5,6-dicyano-1,4-benzoquinone (ddq). The dehydro derivative (2) underw
ent a surprising rearrangement to the triazole (12) upon oxidation with Oxo
ne(R). Several attempts at unambiguous synthesis of the alpha-dicarbonyl de
rivative (3) were unsuccessful; it was obtained, together with the 1,4-dime
thyl derivative (13) by methylation of 3-phenyl-1,4-dihydro-1,2,4-triazine-
5,6-dione (4) with sodium hydride and methyl iodide.