6-Methyl-3-phenyl-1,2,4-triazine-4-oxide

The condensation of amidrazone with isonitrosoacetophenone occurs via formation of the hydrazone 136. The elimination of the ammonia molecule from intermediate 136 yields 3-methyl-6-phenyl-1,2,4-triazine 4-oxide 137 (71LA12). 

The highly 7r-deficient character of the 1,2,4-triazine ring increases the nucle-ophilicity of the methyl group in methyl-1,2,4-triazine A-oxides in reactions with electrophilic alkenes and aldehydes. Thus treatment of the 6-methyl-3-phenyl-1,2,4-triazine 4-oxide 113 with l-(dimethylamino)-l-ethoxyethylene leads to the... 

The reaction of 3-methyl-6-phenyl-l,2,4-tiiazine 4-oxides 117 with nitrobenz-aldehyde leads to the condensation product, 3-(nitrophenylvinyl)-1,2,4-triazine 4-oxides 118. 

When 5-methylthiosemicarbazide is used instead of amidrazone, 3-amino-1,2,4-triazine 4-oxides can be obtained. In this way 3-amino-5-methyl-6-phenyl-1,2,4-triazine 4-oxide 138 was synthesized from isonitrosopropiophenone [52CIL907, 89IJC(B)556]. 

In some cases, the position of the N-oxidation depends on the temperature. The reaction of 3-phenyl-1,2,4-benzotiiazine 172 with peracetic acid affords 3-phenyl-l,2,4-benzotriazine 1-oxide 173 at 50°C and 2-oxide 174 at room temperature (57JCS3186). Only the 1-oxide 175 was obtained by the oxidation of 3-unsubstituted 1,2,4-benzotriazine 176. The oxidation of 3-methyl-1,2,4-benzo-triazine 176 (R = Me) under the same conditions results in a mixture of 3-methyl-l,2,4-benzotriazine 1-oxide 175 and 2-oxide 177 in 25 and 10% yields, respectively. 

Ethyl formate34,52 or orthoformate5 3,54 reacts with two equivalents of phenylhydrazine to yield 1,5-diphenylformazan (11) the reaction takes place under acidic conditions and involves an oxidation. Under basic conditions, ethyl nitrate reacts at the methylene position to yield 3-methyl-1,5-diphenylformazan (37) which can also be obtained from the reaction of phenyl-azoethane (38) with isoamyl nitrite (Scheme 4).8,68 Aryl hydrazines react with a variety of s-triazines (39) to yield 1,5-diaryl formazans with hydrogen, methyl, or phenyl groups in the 3-position as in 40 (Eq. 6).56 Hydrazines have also been reported to react with benzotrichloride55,658 and sym-diamino tetrazine659 to yield formazans. 

Acid hydrolysis of 3-methyl-6-phenyl-l,2,4-triazine 4-oxide (827) yields 4-phenyl-1,2,3-triazole through an acyclic intermediate (828) (Scheme 168) <89AHC(46)73>. 1,2,4-Triazine 2-oxides (829) undergo rearrangement in basic conditions (Equation (80)) to form 4-substituted 2//-1,2,3-triazoles <89AHC(46)73>. l-(2-Nitrophenyl)-5-aryltetrazoles (830) and l-aryl-5-(2-nitrophenyl)tetrazoles are converted into 2-arylbenzotriazoles (831) by refluxing in nitrobenzene (Equation (81)) <81AJC69l>. 

Methyl-3-[N-(l-phenyl-ethyl)-hydroxyamino]- -methylester E16a, 127 (R-NH-OH + En) Pyridin 3-(Dimethoxy-methyl)-4-(fnmy-3-hydroxy-cyclopentyl)-E7b/2, 483 C-[CH(OR)2]-1,2,4-triazin + 3-OH —1-(CO — CH3) — cyclopentan Pyridin-l-oxid 4-Ethoxy-2-(l-hydroxy-cyclohexyl)- E19d. 605 (H - Li/ -(- Keton) Pymolo l,2-a azepin 6-Ethenyl-5-methoxycarbonyl-3-oxo-(5R, 6S, 9aR )-octa-hy dro-E21b, 1974 l-[CH(OH) —... 

X-ray crystallographic analysis of 6-methyl-4-phenyl-l,2,3-triazine 1-oxide (8),22 1-methyl-4,6-diphenyl-l,2,3-triazinium iodide (9),23 4,6-dimethyl-l,2,3-triazine 2-oxide (10a),19 4,6-diphenyl-1,2,3-triazine 2-oxide (10b),19 4,5,6-triphenyl-l,2,3-triazine 2-oxide (10c),36 4,5,6-tris(4-tolyl)-... 

Methyl-,242 3-phenyl-,450 or 3-amino-l,2,4-benzotriazine 1-oxide or -2-oxide afford benzo-triazoles 4 when treated with sodium hydroxide377 The same reaction is observed for pyrido-[2,3-e]-l,2,4-triazin-3-amine or pyrido[4,3-e]-l,2,4-triazin-3-amine 1-oxide in sodium hydroxide affording the corresponding products in 77 and 40% yield, respectively.370 379... 

Oxidation of 6-methyl-3-phenyl-1,2,4-triazine (79) with H2O2 in acetic acid at room temperature gave 6-methyl-3-phenyl-l,2,4-triazin-5-one (80) in 82% yield (Equation (4)) <87CPB1378>. 

The strongly polarized C = C bond of alkynyliodonium salts, along with their propensity for Michael additions, predicts that they should be good 1,3-dipolarophiles. Indeed, reaction of arylethynyliodonium tosylates with arenenitrile oxides, 127, gives a mbtture of cycloadducts, 128 and 129, in 62-80% yields [91] [Eq. (59)]. Similarly, Me3SiC=CIPh OTf and various diazocarbonyl compounds, 130, result [92] in cycloadducts 131 [Eq. (60)]. Likewise, alkynyliodonium salts react with methyl and phenyl azide to give low yields of triazines, 132, as adducts [Eq. (61)]. 

The bond energy E y and the bond length r are related by E y= 1/r thus, there should be a correlation between aromaticity indexes and resonance energies. Accordingly, a unified aromaticity index 7a has been defined (reference benzene 7a=100), and 7a=77 for 1, 86 for 1,2,4- and 100 for 1,3,5-triazine <1992T335>. From molecular dimensions, 7a = 77 has also been calculated for both 4,6-dimethyl- and 4-methyl-6-phenyl-l,2,3-triazine, 73.4 for 4,6-dimethyl-l,2,3-triazine 2-oxide, 76.0 for 4-methyl-6-phenyl-l,2,3-triazine 2-oxide, and 68.95 for 6-methyl-4-phenyl-1,2,3-triazine 1-oxide <1993T8441>. In this sense, N-oxidation is accompanied by a reduction in aromatic character. 

While the parent 1,2,3-triazine 1 is reported not to react with OT-chloroperbenzoic acid (MCPBA) even after 3 days <1992H(33)631>, 4-methyl-1,2,3-triazine 86c, 4,6-dimethyl-l,2,3-triazine 17m, and 4-methyl-6-phenyl-l,2,3-tri-azine 17s gave mixtures of 1-oxides (minor) and 2-oxides (major) when treated with MCPBA or ACOH/H2O2. In contrast, 4,5,6-triphenyl- and 4,6-diphenyl-l,2,3-triazine gave solely the 2-oxides <1996CHEC-II(6)483>. 

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