5- Hydroxy-1,2,4-triazine 4-oxides

The reaction of 1,2,4-triazine 4-oxides 8 bearing substituents at the 3, 5, and 6 positions with peroxyacetic acid proceeds as an N-oxidation process exclusively at the 1 position, resulting in 1,2,4-triazine 1,4-dioxides 14. Oxidation of 1,2,4-triazine 4-oxides 8 unsubstituted at the 5 position leads to 5-hydroxy-1,2,4-triazine 4-oxides 15 (76LA153). 

N,N-diallylmelamine , vasodilator. Rat, dog, man. Extensively metabolized. N-oxidation (triazine ring, reversible reaction) to form active metabolite, then deallylation and N-reduction (rat) direct deallylation (M) (all species) hydroxylation of allyl group N-methylation (triazine ring) then deallylation UP in urine. Species difference - man does not produce active metabolite, (N-hydroxy triazine derivative). 

Phenanthro[l,2-d][l,2,3]selenadiazole, 10,11 dihydro- H NMR, 6, 348 synthesis, 6, 353 Phenanthro[b]thiophenes synthesis, 4, 914 Phenanthro[4,5-bcd]thiophenes synthesis, 4, 883, 907, 914 Phenanthro[9,10-ej[l, 2,4]triazines synthesis, 3, 434 Phenarsazin synthesis, 1, 561 Phenazine dyes, 3, 196-197 nitration, 3, 177 UV Spectra, 2, 127 Phenazine, 3-amino-2-hydroxy-in colour photography, 1, 374 Phenazine, 1-chloro-nucleophilic substitution, 3, 164-165 5-oxide... 

When it was found later that enzymatic oxidation of 2-azaadenine yields its 8-hydroxy derivative (4-amino-6-hydroxyimidazo [4,5-d]-u-triazine), its synthesis was also achieved by the procedure already described/ ... 

Triazine 4-oxides 55 react with phenols (phenol, 2,6-dimethylphenol, resorcinol, 4-hexyh esorcinol) in trifluoroacetic acid in a similar way, yielding intermediate (T -adducts 5-hydroxyphenyl-4-hydroxy-4,5-dihydro-l,2,4-triazines 61. Subsequent oxidation leads to the corresponding 5-hydroxyphenyl-l,2,4-triazine 4-oxides 62 (97MC116). 

The reaction of 1,2,4-triazine 4-oxides 55 with water in the presence of benzoyl chloride affords 3-hydroxy-1,2,4-triazines 78. The mechanism suggested for this reaction includes acylation of the substrate at the oxygen of the iV-oxide group, followed by the addition of water to the 1,2,4-tiiazinium cation and the autoaromatization of the (T -adducts with the elimination of benzoic acid. 

Similarly, ring opening was found in reactions of 6-aryl-1,2,4-triazine 4-oxides 53 with aliphatic amines, yielding open-chain 6-amino-1-hydroxy- 1,4,5-triazahex-atrienes 85. In this case, however, the nucleophile adds to the 3 position of the... 

Open-chain tautomerism is a general feature of 4-hydroxy-3,4-dihydro-1,2,4-triazines, including cr -adducts at position 3 of the 1,2,4-triazine 4-oxides. Thus triazahexatrienes 85 are the open-chain form of cr -adducts 86 and can be aromatized by oxidation with KMn04, yielding 3-amino-1,2,4-tiiazine 4-oxides 88 (98ZOR418). 

The 1,2,4-triazine 4-oxides 55 were synthesized by the reaction of nitrones 158 (generated from a-hydroxylamino ketones and aldehydes) with an excess of hydrazine, followed by the oxidation of the intermediate 4-hydroxy-2,3,4,5-tetrahydro-l,2,4-triazines 159 with lead(TV) oxide (73KGS134). 

In the presence of hydroxy or perhydroxy radicals generated from Fenton s reagent, atrazine undergoes oxidative dealkylation in aqueous solutions (Kaufman and Kearney, 1970). Major products identified by GC/MS included deisopropylatrazine (2-chloro-4-ethylamino-6-amino-s-triazine), 2-chloro-4-amino-6-isopropylamino-5-triazine, and a dealkylated dealkylatrazine (2-chloro-4,6-diamino-s-triazine) (Kaufman and Kearney, 1970). 

Data on the structures of monocyclic dihydro- or hexahydro-1,2,3-triazines, on 1,2,3-triazine tV-oxides and 1,2,3-triazinones are not yet available. From studies on the one-electron reduction of the tetrahydro-l,2,3-triazinium salts (7) it was concluded that the heterocyclic ring is flexible and not planar (80LA285). No detailed information on the structure of 3-benzyl-l,5-diphenyl-l,2-dihydro-l,2,3-triazine-4,6(3//,5f/)-dione (8) or of the 6-hydroxy-4-oxo-l,4-dihydro-l,2,3-triazinium hydroxide inner salts (9) seems to be available. 

Naphthoquinone 1-oxime (772) reacts with aminoguanidine (773) and similar compounds to give 2-aminonaphtho[ 1,2-e][1,2,4]triazine 1-oxides (774). 1-Hydroxy-naphtho[l,2-e][l,2,4]triazin-2-ones can be prepared in an analogous reaction <78HC(33)189, p. 728). 

Further analysis of celery samples taken from the aforementioned study characterized 14 metabolites. These structures included simple hydroxy-x-triazines (GS-11526, GS-17794, GS-11957, GS-17791, GS-35713, and cyanuric acid), side-chain oxidized hydroxy-x-triazines (MCO-III-25 and MCO-IV-34), oxidized parent metabolites (GS-16141 and GS-16158), and dealkylated fiiiomethyl-x-triazines (GS-11354 and GS-26831). A metabolic pathway for prometryn in celery is illustrated in Figure 7.9. 

It has been successful to isolate intermediates and to identify them by NMR spectroscopy as 3-aryl-6-dialkylamino-l-hydroxy-1,4,5-triaza-1,3,5-hexatriene. Treatment with potassium permanganate of these open-chain structures gave ring closure into 3-dialkylamino-l,2,4-triazine-4-oxides. Also, in these reactions it was observed that the regiospecificity of the addition is temperature dependent. Whereas at —40°C the addition occurs at C-3, at -70 °C the addition takes place at C-5 (01H127). Whether on oxidation at —70°C the 5-dialkylamino-6-phenyl-l-2-4-triazine-4-oxide is formed is unknown. 

Reaction of the triazine 1-oxides (54a,b) with HN02 gave the corresponding 3-hydroxy derivatives (204a,b) in 88% and 78% yield, respectively. Subsequent treatment of compounds (204a,b) with hot... 

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