1.2.4- Triazines uracils

Interference by certain phenylurea and tf-phenylcarbamate herbicides with the photochemical reactions of isolated chloroplasts was first reported in 1956 (2). Over the next few years, inhibition by the s-triazines, uracils, benzimidazoles, and ben-zonitriles was reported 3, 6). ... 

The Hill reaction has served as a target for structure-activity studies with phenylureas, iV-phenylcarbamates, polycyclic ureas, acylanilides, s-triazines, uracils, dihalogenated benzoni-... 

Many infinite 2-D assemblies have also been constructed including (but not limited to) piperazine carboxylic acid [108], trithiocyanuricbipyridine [109], pyr-idyloxamide dicarboxylic acid [110], picolylaminocyclohexenone dicarboxylic acid [111], triazine uracil [112], tris-(4-pyridyl)triazine trimesic acid [113], bipyridine ur-eylene dicarboxylic acid [76] and isonicotinamide dicarboxylic acid [93, 114], Scheme 2.5.16. 

The use of herbicides that inhibit or interact with the photosynthetic machinery is seen, superficially, to be advantageous because of the likelihood of fewer problems of animal toxicity. However, the identical nature of the process in both crop and weed species, apart from C4 plants, means that herbicide selectivity must be achieved by differential uptake, movement, or metabolism. Following the discovery of the herbicidal action of N (4-chlorophenyl)-N,N-dimethylurea (subsequently known as CMU or monuron) by Bucha and Todd in 1951, Wessels and Van der Veen and Cooke showed that this compound was a potent inhibitor of photosynthetic electron transport. This, the first so-called Hill reaction inhibitor, was followed subsequently by numerous other phenylureas, triazines, uracils,... 

Malachite green (0.0...2.0) uracil derivatives, triazine herbicides [163] polar lipids [246, 247] phospholipids [248, 249] fatty acids, fatty aldehydes, phospholipids and glycolipids [250] microbiocidal isothiazolones [251]... 

By comparing the dissociation constant of 6-azauracil and 6-aza-uridine with those or uracil and uridine, 6-azauridine is now considered to be 1-ribofuranosyl derivative (2-ribofuranosyl-3,5-dioxo-2,3,4,5-tetrahydro-l,2,4-triazine), The same was shown more exactly by comparing the UV and IR spectra and the dissociation constants of 6-azauridine with the two monomethyl derivatives of 6-aza-uracil," Enzymatic synthesis thus, proceeds, in the same way in natural bases and in their aza analogs. 

Direct bromination readily yields the 6-bromo derivative (111), just as with uracil. Analogous chlorination and iodination requires the presence of alkalies and even then proceeds in low yield. The 6-chloro derivative (113) was also obtained by partial hydrolysis of the postulated 3,5,6-trichloro-l,2,4-triazine (e.g.. Section II,B,6). The 6-bromo derivative (5-bromo-6-azauracil) served as the starting substance for several other derivatives. It was converted to the amino derivative (114) by ammonium acetate which, by means of sodium nitrite in hydrochloric acid, yielded a mixture of 6-chloro and 6-hydroxy derivatives. A modified Schiemann reaction was not suitable for preparing the 6-fluoro derivative. The 6-hydroxy derivative (115) (an isomer of cyanuric acid and the most acidic substance of this group, pKa — 2.95) was more conveniently prepared by alkaline hydrolysis of the 6-amino derivative. Further the bromo derivative was reacted with ethanolamine to prepare the 6-(2-hydroxyethyl) derivative however, this could not be converted to the corresponding 2-chloroethyl derivative. Similarly, the dimethylamino, morpholino, and hydrazino derivatives were prepared from the 6-bromo com-pound. ... 

It may be said in conclusion that the reactivity of position 5 (i.e., 6 of the triazine ring) is similar to that of uracil. The only difference seems to be in the failure to prepare 5-nitro-6-azauracil although this reaction proceeds readily with uracil. 

On reaction with aged phosphoroxychloride, 6-azauracil formed 3,5-dichlorotriazine (117) in only a 10% yield. " A somewhat higher yield (30%) was obtained from the reaction of 6-bromodioxotriazine which gave 3,5,6-trichloro-l,2,4-triazine. Similar reactions take place much more readily with uracil and in better yield. " Thus,... 

Zazza C, Amadei A, Sanna N, Grandi A, Chillemi G, Nola AD, D Abramo M, Aschi M (2006) Theoretical modeling of the valence UV spectra of 1,2,3-triazine and uracil in solution. Phys Chem Chem Phys 8 1385-1393... 

Treatment of 3-methyl-6-(l-methylhydrazino)uracil 262 with phenacyl bromides in ethanol afforded (78H1571 81CPB379) the pyrimido-[4,3-c][l,2,4]triazines 264 in addition to 263. 

A kinetic study of alkaline hydrolysis of reumycin 311 indicated that OH added reversibly to C-5 to form an intermediate 408, which then decomposed to the triazine 409 (88MI2). At high OH concentrations, the rate-limiting step was the attack of OH on C-5 of 311, whereas at low OH concentrations it was the cleavage of the uracil ring in intermediate 408. 

Treating glycosyl isothiocyanates 415 with 5,6-diamino-1,3-dimethyl-uracil (416) gave thioureas 417, which on oxidative cyclization with N-bromosuccinimide afforded 5,7-dioxopyrimido[5,4- ][1,2,4]triazine nucleosides 418 (80MI1 82MI2). 

C, Inhibition of photosynthesis at photosystem II 1,3,5-Triazines Triazinones Uracils Pyridazinone Phenyl carbamates 5... 

Carbamate, thiocar-bamate, pheny-lureas, triazines, acetanilide, uracil, propionalide, benzonitrile, benzamide, di-carboximide, dinitroaniline, pyrethroid, thiadi-azinone, metoxy-benzoic, phenol, phenoxy acid, coumarin... 

Considering tridentate sites, 2,6-diaminopyridine and uracil are complementary single site groups (see Sections 9.4.2 and 9.4.3 below). On the other hand barbituric acid (BA) and 2,4,6-triaminopyrimidine (TAP) or -triazine (TAT) are Janus molecules containing two identical recognition sites while 168 is plerotopic by virtue of its two complementary sites (see Section 9.4.4). 

Triazine, urea, N-phenyl carbamate, tbiocarbamate, substituted aniline and uracil types Corn, potatoes, carrots GC-MS 0.1 ppm [144,145]... 

In summary, triazine resistance in weeds is most commonly due to a target site alteration that confers a very high level of resistance to. y-triazinc herbicides. Although a Ser264 to Gly mutation in the D1 protein is most common, additional alterations have been identified that confer resistance to triazines and other classes of PS II inhibitors. Enhanced herbicide metabolism plays a major role in conferring resistance in only a few weed biotypes. In these biotypes, the pattern of resistance may be broader, with some cross-resistance to av-trazinones, uracils, heterocyclic ureas and phenyl ureas. The level and pattern of resistance to various herbicides in these biotypes depend, presumably, on the activity and specificity of the enzyme(s) responsible for the enhanced herbicide metabolism. 

The herbicides commonly used as arboricides include members of the triazines, ureas, and uracils, for grass and weed control in nursery and Christmas tree plantings. Other compounds include phosphonate and phosphate derivatives, pyridine-based organic acids of high activity, and organic arsenicals. Such a wide... 

More than 130 different organic chemicals are currently employed as herbicides in the U.S. All of the main families of organic compounds are represented aromatic, aliphatic, and heterocyclic. Herbicidal activity is found in a variety of classes of compounds haloaliphatic, phenoxy, and benzoic acids carbamates dinitroanilines acetanilides amino triazines quaternary pyridinium salts uracils and ureas. A few selected key examples are reviewed below. 

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). 

Bifunctional nucleophilic compounds can add to TV-alkylpyrazinium salts, and the benzo fused pyrazino[2,3-e][l,3,4]thiadiazine (471) as well as the benzo fused pyrazino[2,3-e]-l,2,4-oxadiazine (472) can be made by this method (Scheme 40). A closely related reaction is exemplified by the preparation of the pyrazino[2,3-e]-1,2,4-triazine (473) (Equation (94)) <87KGS557, 87KGS1118). The pyrimido[5,4-c][l,2,5]oxadiazine (475) can be prepared by treatment of the uracil derivative (474) with isoamyl nitrite (Equation (95)). Presumably the reaction proceeds by cyclization of an initially formed 5-nitrosopyrimidine intermediate (64ZC454). 

Azine approach. The fused uracil (58) has been prepared from 5-amino-l,3,6-trimethyl-uracil diazotization of the latter yields a fused triazine A-oxide (57), which has its triazine ring transformed into an isoxazole ring by tin(II) chloride treatment (62USP3056781). 

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