Syntheses in the 4,5-dihydro-1,2,4-triazin-6-one-series

Dihydro-1,2,4-triazin-6(1H)-ones. II Synthesis of Several Methylated 3-Phenyl- 4,5-dihydro-1,2,4-triazin-6(1H)-ones

“…However, when the reaction was repeated at −78 • C the yield of 3-phenyl-4,5-dihydro-1,2,4-triazin-6(1H )-one (15) was much better (59%). The melting point and spectroscopic data were consistent with those reported by Andersen et al 18 Methylation of the 3-Phenyl Dihydrotriazinone (15) While 1,2,4-triazin-5(4H )-ones feature prominently in the reviews 19 of the alkylation of 1,2,4-triazine derivatives, the only papers found on the alkylation of 1,2,4-triazin-6(1H )-ones or their derivatives are those by Prokoféva et al 20 and Camparini et al 2 There are five possible monomethylation products of 3-phenyl-4,5-dihydro-1,2,4-triazin-6(1H )-one (15), namely, (8), (9) and (22)-(24). We found that treatment of compound (15) with 1 mole equiv.…”

“…The 1 H and 13 C n.m.r. spectra of (20) showed methyl resonances at δ 1 · 41 and 25 · 0, respectively.…”

“…Reaction of an excess of hydrazine hydrate with the freshly prepared imidoyl chloride (21) in anhydrous dichloromethane gave the new 5,5-dimethyl-3-phenyl-4,5-dihydro-1,2,4-triazin-6(1H )-one (20) in 92% yield. The 1 H and 13 C n.m.r.…”

“…* Therefore it was necessary to determine if the net biological activity observed for compounds of type (16) was due to the parent compound or its aerial oxidation products (Scheme 4). In this respect, it was of interest to prepare 5,5-dimethyl-3-phenyl-4,5-dihydro-1,2,4-triazin-6(1H )-one (20) in which aerial oxidation at C 5 is precluded.…”