5,6-Diphenyl-l,2,4-triazine-3 -one

Benzil monohydrazone (610) and urea are reported to form 5,6-diphenyl-l,2,4-triazin-3-one (611) (71MI21903), and a-hydrazonocarboxylic acids (612) can be cyclized with imidates to l,2,4-triazin-5-ones (613) (74T3171). Both these reactions can also be treated as [2+2 + 2] syntheses, since the hydrazones (610) and (612) are prepared from the appropriate ketones and hydrazine. 

From the reaction of 6-phenyl-l,2,4-triazine-3,5-dione (157) with phenylmagnesium bromide, 5,6-diphenyl-l,2,4-triazin-3-one (27), 3,5,6-triphenyl-1,2,4-triazine (147), 3,3,5,6-tetraphenyl-2,3-dihydro-l,2,4-triazine (158), 2,4,6-triphenyl-l,3,5-triazine (148) and 2,4,4,5-tetraphenylimidazole (149) were isolated (71JPR699). From the results obtained in the reaction of 3,5,6-triphenyl-l,2,4-triazine (147) with phenylmagnesium "bromide it can be supposed that the last two compounds were formed via the intermediate formation of (147). 

Reaction of 5,6-diphenyl-l,2,4-triazin-3-one (215) or 5,6-diphenyl-l,2,4-triazine-3-thione (216) with benzene under Friedel-Crafts conditions led to the isolation of 5,5,6-triphenyl-4,5-dihydro-l,2,4-triazin-3-one (217) and -3-thione (218) respectively (76IJC(B)273). Reacting under similar conditions (C6H6/AlCl3) the 6-styryl compounds (219-221) are converted into the corresponding 6-(2,2-diphenylethyl) derivatives, e.g. (222) from (219) (75IJC1098). 

The C-3 adduct 37, presumed earlier to be the structure of the product obtained on refluxing 3-chloro-5,6-diphenyl-l,2,4-triazine in a water-ethanolic solution, was not detected the product was found later to be 5,6,-diphenyl-l,2,4-triazin-3-one (Scheme 25) (82CPB152). 

Reaction of 3-chloro-5,6-diphenyl-l,2,4-triazine with phenylmagnesium bromide has been found to result in a rather complex mixture of 12 products ), including tetraphenylimidazole (169) and triphenylimidazolone 172. 2,5-Dihydro-1,2,4-triazines 168 and 171, resulting from the addition of the Grignard reagent at C-5 of 3,5,6-triphenyl-l,2,4-triazine 167 and 5,6-diphenyl-l,2,4-triazin-3-one 170, are postulated as the key intermedi-... 

Many 1,2,4-triazines form complexes with metal ions and can be used for their determination. Thus, 3- and/or 5-(2-pyridyl)-substituted 1,2,4-triazines (e.g. 820) can be used for the determination of iron (II), cobalt(II), nickel(II), zinc(II) and copper(I) ions, thallium and palladium ions can be analyzed by 6-phenyl- (821a) and 5,6-diphenyl-l,2,4-triazine-3-thione (821b), while osmium can be determined by 3-thioxo-l,2,4-triazin-5-one (822), 3-thioxo-dihydro-l,2,4-triazin-5-one (823), 6-mercapto-l,2,4-triazine-3,5-dione (824a), 6-mercapto-5-thioxo-l,2,4-triazin-3-one (824b) and 3,5-dithioxo-l,2,4-triazine-6-carboxyl-ates (825) <78HC(33)189, p. 1004). 

Sion of carbon monoxide. Thus 5,6-diphenyl-l,2,4-triazine-3(2H)-one (1) is converted into 4,5-diphenyltriazolc (2) in 94% yield. Chloramine is thus acting as an oxidant, probably with initial N-chlorination. 

Reaction of 5,6-diphenyl-l,2,4-triazin-3(2//)-one with ethyl chloroacetate and potassium carbonate in dry acetone gives ethyl (5,6-diphenyl-l,2,4-triazin-3-yloxy)acetic acid (189) (Equation (17)) <83JHC507>. 

Diphenyl-l,2,4-triazin-3(2H)-one allowed to react at room temp, with ethereal chloramine 4,5-diphenyl-l,2,3-triazole. Y 94%. F. e. s. C.W.Rees and A. A. 

Phenylmagnesium bromide converts 3-amino-6-phenyl-l,2,4-triazin-5-ones (164) into 3-amino-5,6-diphenyl-l,2,4-triazines (165) (73JPR221). 

To a stirred solution of but-3-ynamine (897 mg, 13 mmol) in anhyd THF (20 mL) at 0 rC was added as a solid in one portion 3-(methylsu)fonyl)-5,6-diphenyl-l,2,4-triazine (1.75 g, 5.0 mmol). The resultant mixture was stirred at rt with exclusion of moisture for 24 h. Sat. aq NaHCO, (20 mL) was then added, and the aqueous mixture was extracted with CH2C12 (3x20mL). The combined CH2CI2 extracts were dried (MgS04) and evaporated under reduced pressure. The residue was titurated with Et20 and then recrystallized (EtOAc) yield 1.45 g (97%) yellow needles mp 131 132°C. 

IIydrazino-5,6-diphenyl-l,2,4-triazine reacts with 4-arylidene-2-phenyloxazol-5(4//)-ones and 4-benzylidene-3-methylisoxazol-5(4//)-ones in toluene to afford products 19 and 20, respectively, substituted in the hydrazino group.299... 

Morpholino-6-phenyl-l,2,4-triazin-5(2//)-one (190) afforded the 4-methyl derivative (191) upon treatment with methyl iodide, which with water gave 4-methyl-6-phenyl-l,2,4-triazine-3,5(2/f,4//)-dione (192). 3-Morpholino-5,6-diphenyl-l,2,4-triazine (193) was isolated from the reaction of (190) with phenylmagnesium bromide (Scheme 37) <88LA141>. 

Similar ring contractions in which the nitrogen-nitrogen bond is cleaved are found in the reductive ring contractions of pyridazines to pyrroles [148, 149], phthalazines to isoindoles [150], 5,6-diphenyl-1,2,4-triazinones to imidazolones [151], benzo-l,2,4-triazines to benzimidazoles [71], benzo-l,2,3-triazinone to indazolone [la, 152], benzo-l,2,3-triazin-3-oxide to indazole [la], benzo-2,3-diazepines to isoquinolines [153], benzo-l-pyrano-[4,3-e ]-as-triazin-3-one to benzopyranoimidazolone [154], and 2-methyl-4,5-dihydropyridazin-3-ones to pyrrolin-2-ones [155]. 

Nitrosation of l,2,4-triazin-3-amine 2-oxides and subsequent thermolysis of the thus formed diazonium tetrafluoroborate salts 9 affords 3-fluoro-l,2,4-triazine 2-oxides 10 in one example, the 5,6-diphenyl-substituted diazonium tetrafluoroborate 9 (R1 = R2 =- Ph) was isolated as the first stable heterocyclic diazonium salt.98... 

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