6- Phenyl-1,2,4-triazine- 1-oxide, oxidative

The methoxy group is replaced in the reaction of 3-methoxy-5-phenyl-1,2,4-triazine 1-oxide 46 with ammonia, resulting in 3-amino-5-phenyl-1,2,4-triazine 1-oxide 47. The treatment of 3-methoxy-1,2,4-triazine 1-oxide 20 with hydrazine leads to 3-hydrazino-1,2,4-triazine 1-oxide 48 (71JOC787). 

The reaction of 3-methoxy-1,2,4-triazine 1-oxide 20 with the carbanion generated from chloromethyl phenyl sulfone proceeds as the vicarious nucleophilic substitution (VNS) of hydrogen (Scheme 1, path B) via addition of the carbanion at position 5 of the heterocycle. Following base-induced elimination of HCl and protonation, 3-methoxy-5-phenylsulfonyl-1,2,4-triazine 4-oxides 65 result (88LA627). 

At the same time, the reaction of 1,2,4-triazine 4-oxides 55 with the anion of chloromethyl phenyl sulfone affords 5-(l-chloro-l-phenylmethyl)-l,2,4-triazines 66. In this case, autoaromatization of the a -adducts proceeds by the deoxygenative... 

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. 

The reaction of hydroxyamidrazone 134 with dimethylglyoxal in methanol leads to 5,6-dimethyl-3-phenyl-1,2,4-triazine 4-oxide 135 (71LA12). 

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-l,2,4-triazine 4-oxide 137 (71LA12). 

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. 

In a sequence of cycloaddition and cycloreversion, 3-phenyl-l, 2,4-triazine 1-oxides react with benzyne, generated from 2-aminobenzoic acid (see Houben-Weyl, Vol. 5/2 b, p 622 ff), to give 2-phenyl-l, 3-benzoxazepines in moderate yield.419... 

Phenyl-l,2,4-triazine 4-oxide 91 reacts with l,3-dimethyluracil-6-hydrazones 92 in DMF in the presence of triethylamine to give pyrazolo[3,4-. 

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. 

HPA = (4-pyridylthio)aceticacid 2-fur = 2-furoate a-fur = a-furoate = ([Pg.116]

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>. 

Ebenfalls iiber ein Nitren sollte die Oxidation des N-Phenyl-amidinium-Salzes I mit Natriumhypochlorit fiihren es cyclisicrt zu 2-(4,6-Bis-[dimethylamino]-l,3,5-triazin-2-yl)-benzimidazoln9 ... 

In a similar reaction, 2-(o-nitrophenyl)ethylamine (100) may be reduced in an ammonia buffer to the hydroxylamine and oxidized to the nitroso derivative, which condenses with the amino group to a dihydrocinnoline.160,161 It is also possible to prepare dihydrobenzo-l,2,3-triazinones on reduction of o-nitrobenzhydrazide, followed by oxidation of the hydroxylamine to a nitroso group, and 3-phenyldihydrobenzo-l,2,3-triazine (101) from N-phenyl-(V-(o-nitrobenzyl)hydrazine (100) in an analogous way161 [Eq. (78)]. 

Pyrolysis of 4-phenyl-l,2,3-benzotriazine 3-oxide (100) at 420 °C gave 3-phenylbenz-isoxazole (101), 3-phenylindazole (102) and acridin-9-one (103). However, the pyrolysis of 4-phenylnaphtho[2,3-. 

When 3-phenyl-l,2,4-triazine (411) reacts with the enamine (406), orientation B is followed. In this case the 3,4-dihydropyridine (412) is formed and is isolated. Elimination of the amine directly is unfavourable, because of the cis orientation, and transfer of the proton to the pyridine nitrogen is impossible. Oxidation to the (V-oxide (413) and Cope elimination affords the condensed pyridine (414) (78UP21900). 

There have been reviews of nucleophilic substitution103 and of deoxidative nucleophilic substitution 104 in heterocyclic A -oxidcs. Stable carbon-carbon-bonded adducts, such as (22), have been reported from the reactions of 6-phenyl-1,2,4-triazine 4-oxides with phenols oxidation of the adducts may be achieved by reaction with potassium permanganate in acetone.105... 

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