1,2,4-Triazinone

Compound 961 has been converted into 3-amino-6-azido-5(2//)[ 1,2,4]tri-azinone 1041, which was employed in a study of azide-tetrazole equilibrium affording 6-amino-8(5//)tetrazolo[5,1-/][1,2,4]triazinone 1042 (79JHC555) (Scheme 196). 

Some 1,2,4-triazines having a 1,2,4-triazinone substituent, and some 1,2,4-triazolo[4,3-fc]-1,2,4-triazinones have been shown to have in vitro anti-HIV and anticancer activity < 95MI04 96CA(124)86961 >. 

Reaction of hydrazonoyl halides 40 with 4-amino-23-dihydro-6-substituted-3-thioxo-1,2,4-triazinones 39 gives l,2,4-triazino[43-h][l,2,4,5]tetrazine derivatives 41 <00JPR96>. 

Table 3 13C and 15N NMR data of some imidazo- and thiazolo[1,2,4]triazinones 50 measured in dimethyl sulfoxide (DMSO) solution... 

Under much milder conditions, the same reaction occurs with 1,2,4-triazinone 164, resulting in the formation of a l,3,4-thiadiazolo[2,3-c][l,2,4]triazinium cation 165 (Scheme 64) (88H1935). Another cationic product is obtained upon conversion of dithiocarbazate to carbodiimide, which occurs via iminophosphorane formation and aza-Wittig reaction with... 

In the reaction of heterocyclic amidrazones with DMAD, condensed 1,2,4-triazinones have been reported. Cherkasov et have studied the reaction of the formazan (141) with DMAD and have shown that the 1,3,4-dihydrotriazine derivative (142) and a 1 1 adduct (143) are formed in this reaction [Eq. (23)]. 

An example of the first case is provided by the 1,2,4-triazinone side-chain aldehydes (102a) which exist in equilibrium with the cyclized forms (102b). 

Amino groups are relatively stable toward exchange by other nucleophiles. Hydrolysis, leading to 1,2,4-triazinones, is the reaction most often observed. The transformation of an amino group into a chloro substituent by nitrous acid in the presence of chloride ions has also been reported (Scheme 11). 

Herbicides that seem to have a single site of action on the photochemical pathway, which is associated closely with photosystem 11 are the chlorinated pheny 1 ureas, Ws-carbamates such as phenmedipham, chlorinated s-triazines, substituted uracils, pyridazinones, diphenylethers, 1,2,4-triazinones, azido-s-triazines, cyclopropane-carboxamides, p-alkylanilides, p-alkyl-thioanilides, aminotriazinones, and urea-carbamates (2). 

Figure 5. 1,2,4-Triazinones tested and contributions made by molecular substituents in the inhibition of photosystem II [adapted from Draber et al. (15)]...

The azo compound PhN=NCONH2 reacts with morpholinocyclohexene to yield the spiro-triazolinone 163, whereas with pyrrolidinocyclohexene the bicyclic 1,2,4-triazinone 164 is formed (equation 74)94. 

Title Substituted Polycyclic Aryl and Heteroaryl 1,2,4-Triazinones Useful for Selective Inhibition of the Coagulation Cascade M.S. South et al, US Patent 7,015,223 (March 21, 2006)... 

It is not enough for a multiple parameter equation just to work and to give an improved correlation as Higuchi and Davis have emphasized recently (64). The correlation must have a physicochemical significance. Recently, Equation 31 has been presented by Biichel and his co-workers for the inhibition of the Hill reaction with 1,2,4-triazinone herbicides (65). 

Several compounds of this class (354) have been made by condensation of the 1,2,4-triazinone derivatives 355 (R = SMe) with orthoesters or acid chlorides. These betaines (354) form deeply colored methiodides (356) whose chemistry has been investigated. 

When the dihydro-1,2,4-triazinone (194) is heated at 180 °C under reducing conditions there is rupture of the 1,2-bond followed by ring closure, producing 4,5-diphenyl-imidazolinone (195). Such reductive ring closures of benzotriazine 1-oxides (196) can give benzimidazoles, in particular 2-(4-thiazolyl)benzimidazoles (197) ( thiabendazole ). Similar reactions take place with 1,3,5-triazines. In fact, primary amines cleave the compounds completely with evolution of ammonia and formation of iV.iV -disubstituted formamidines. With suitable primary amines, though, this reaction can be designed to produce imidazolines or benzimidazoles (Scheme 113). 

When the dihydro-1,2,4-triazinone 76 is heated at 180°C with red phosphorus and hydroiodic acid, there is rupture of the 1,2-bond and subsequent ring closure to give 4,5-diphenylimidazolin-2-one (77) (see Scheme 17) and reductive ring contractions to imidazoles (81) have also been reported " in the 1,3,5-triazine series. A further interesting ring contraction is that which occurs when 4H-l,3,5-thiadiazines (78) are treated with aliphatic amines at room temperature. The triarylimidazoles (81) may be formed by initial formation of the 1,3,5-thiadiazine anion (79) which probably loses sulfur... 

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]. 

Alkylations. A -Methylation of methylthiopyrimidinones and 1,2,4-triazinone with MeOH over HY-zeolite takes place at 210°. 

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