Transformations of 6-Phenyl-1,2,4-triazine 4-Oxides in Reactions with Nucleophiles

Synthesis, thermal transformations, and mass spectrometric fragmentation of 4,4'-[1,2-bis(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)ethane-1,2-diyl]-bis(5-methyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one)

“…Yield 0.025 g (23%). The 1 H NMR spectra of compounds 3 and 4 were identical to those described in papers [4,5], respectively. Compound 4.…”

“…The filtrate was cooled, and the precipitate of 4-[(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)methylidene]-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one (4) was isolated. Yield 0.025 g (7%), orange crystals, mp 180-182°C (mp 181-182°C [5]). The filtrate was neutralized to pH 7-8 and extracted with CHCl 3 .…”

“…We have found that unsubstituted quinoxaline reacted with 1,3-dimethylbarbituric acid at room temperature to form monosubstituted product in the absence of external acid-base catalysis, and we described a reaction of quinoxaline with ethyl 3-[(1,3-dimethyl-2,6-dioxotetrahydropyrimidin-4(1H)-ylidene)hydrazono]butanoate on heating in an acidic medium with the formation of 6,8-dimethylpyrimido[4,5-c]pyridazine-5,7(6H,8H)-dione [3].We recently published a preliminary report on an unusual reaction of quinoxaline (1) with 3-methyl-1-phenylpyrazol-5-one (2) in the presence of triethylamine [4], forming 4,4'-[1,2-bis(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)ethane-1,2-diyl]bis(5-methyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one) (3) in 47% yield and the known 4-[(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)methylidene]-5-methyl-2-phenyl-2,4-di-hydro-3H-pyrazol-3-one (4) [5] in 7% yield (Scheme 1). In addition, o-phenylenediamine (5) was also isolated from the reaction mixture.…”

“…We recently published a preliminary report on an unusual reaction of quinoxaline (1) with 3-methyl-1-phenylpyrazol-5-one (2) in the presence of triethylamine [4], forming 4,4'-[1,2-bis(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)ethane-1,2-diyl]bis(5-methyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one) (3) in 47% yield and the known 4-[(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)methylidene]-5-methyl-2-phenyl-2,4-di-hydro-3H-pyrazol-3-one (4) [5] in 7% yield (Scheme 1). In addition, o-phenylenediamine (5) was also isolated from the reaction mixture.…”

A simple means of preparing quinoxaline derivatives: direct introduction of C-nucleophiles into the quinoxaline nucleus by substituting a hydrogen atom

“…In fact, the reaction of I with 1-phenyl-3-methylpyrazol-5-one in the presence of triethylamine yielded the known dipyridylmethane (VII) [9] and 1,1,2,2-tetra(5-methyl-3-oxo-2-phenyl-1,2-dihydro-3H-pyra zol-4-yl)ethane (VIII). In addition, preparative thin-layer chromatography on silica gel was used to isolate o-phenylenediamine IX from the reaction products (scheme 2).…”