2- -4,6-trisubstituted triazines

In acetonitrile, reduction potentials have been determined for 22 substituted 1,2,4-triazines.347 3,5-Disubstituted and 3,5,6-trisubstituted triazines show reversible behavior, with the formation of the corresponding anion-radicals the anion-radicals from 5-unsubstituted triazines are less stable and react probably by dimerization. 

The position of the tautomeric equilibrium in the trisubstituted triazines 138 depends on the nature of substituents both in the heteroaromatic ring and in the side chain. The enamine structure 138b was ascribed to the triazines 138 (R1 = COOMe, COOEt R2 = CN R3 = OMe) (78RTC107, 88KG241), whereas triazine 138 (R1 = R2 = CN R3 = OMe) favors the non-aromatic tautomer 138c. Malonic diester-functionalized... 

In contrast to the above examples of nucleophilic ring cleavage which are exclusive to 1,3,5-tri-azine, a reaction of trisubstituted triazines 13 with arylhydrazines, e.g. 14, can be effected by heating at 190°C for half an hour to give the corresponding formazans 15 in about 50% yield.21... 

One approach to detecting hemilability is to provide an alternative donor within the ligand. The 2,2 -bipyrimidyl ligand 23 is useful in this regard (Scheme 17). Interconversion of the H4 and H6 is indicative of the Pd-N bond rupture. This approach for detection of Pd-N bond rupture has also been used for pyrazolylpyiimidines and trisubstituted triazines. ... 

Triazines. The application of sulfone as a safety-catch linker has also been demonstrated by Chang and coworkers in their orthogonal synthesis of highly pure trisubstituted triazines 37 (Scheme 12.9). Polystyrene thiophenol resin was hrst coupled with the triazine 33 to yield the polymer-bound resin 34. The chlorinated site... 

Organic Derivatives. Although numerous mono-, di-, and trisubstituted organic derivatives of cyanuric and isocyanuric acids appear in the hterature, many are not accessible via cyanuric acid. Cyanuric chloride 2,4,6-trichloro-j -triazine [108-77-0], is generally employed as the intermediate to most cyanurates. Trisubstituted isocyanurates can also be produced by trimerization of either aUphatic or aromatic isocyanates with appropriate catalysts (46) (see Isocyanates, organic). Alkylation of CA generally produces trisubstituted isocyanurates even when a deUberate attempt is made to produce mono- or disubstituted derivatives. There are exceptions, as in the production of mono-2-aminoethyl isocyanurate [18503-66-7] in nearly quantitative yield by reaction of CA and azitidine in DMF (47). 

Because of the ease of ring synthesis, symmetrically trisubstituted s-triazines have been more thoroughly studied, but a few nucleophilic substitutions of derivatives bearing a single leaving group are known. 2-Chloro-4,6-diphenyl- and 2-chloro-4,6-dimethyl-s-triazines (318) undergo facile nucleophilic displacements with ammonia, amines, and hydrazine, with alkoxide, or with hydrosulfide... 

Tricyano-s-triazine (322) is mono-substituted very rapidly with anhydrous methanol (20°, few min) and with water di- and trisubstitution products also result under mild conditions (65°, one min, and 65°, several hr, respectively, for methanol). 

The rapid synthesis of 1,2,4-triazines has also been developed under microwave-assisted conditions [80]. Irradiation of a 1,2-diketone with acyl hydrazides and ammonium acetate for 5-10 min at 180 °C in a single-mode microwave reactor gave 3,5,6-trisubstituted 1,2,4-triazines in excellent yield and purity and reaction times that were reduced 60-300 fold over conventional conductive heating methodology (Scheme 22). 

A different kind of triazine, 3,5,6-trisubstituted 1,2,4-triazines 166, were prepared by reaction of 1,2-diketones 164 with acyl hydrazide in the presence of ammonium acetate and acetic acid at 180 °C for 5 min under microwave irradiation in a sealed tube [107]. Different substituents can be introduced in the final triazines providing a general approach for this kind of heterocycles (Scheme 59). 

A convenient synthesis of trisubstituted 1,3,5-triazines uses acylamidines 1 and amidines < 95JOC8428 >, whilst l,3,5-triazin-2(l/f)-ones 3 are obtained from N-acyl-lV -carbamoyl-S-methylisothioureas 2 <96H(43)839>. 

Tris(trinitromethyl)-l,3,5-triazine reacts with nucleophiles such as alcohols and amines to give products in which the trinitromethyl groups are displaced in turn to yield mono, di, then trisubstituted compounds. Some of the products which have been obtained are shown in Scheme 12 <95CHE(31)596>. 

The synthesis of 2,4,6-trisubstituted-l,3,5-triazines has been reviewed <06MI81>. Reaction of an activated form of carboxylic acids 20 with zinc dimethyl imidodicarbonimidate 21 led to 4,6-dimethoxy-l,3,5-triazines 22 in high yields <06S2845>. 

A novel route to synthesize l,3 -triazine-2,4(l//,3//)-diones through the desulfurization of thiocarboamides, such as 1,3-disubstituted 2-thioureas, trisubstituted thioureas and N-substituted thioamides by silver cyanate has been reported <00H(53)929>. Treatment of urazole 23 with one equivalent of sodium hydride under anhydrous conditions, followed by addition of dimethyl sulfate, leads to l,3,5-triazine-2,4-dione 24 in 80% yield . 

No reaction occurred with 1,4,5-trisubstituted biguanides (e.g. 1-p-chlorophenyl-4,5-dimethylbiguanide) and acetone in basic media. Prolonged action under acid conditions gave small amounts of a picrate which appeared to correspond to the triazine (CXL). 

Thermolytic rearrangement of 1,2,3-trisubstituted cyclopropenyl azides constitutes the only proven method at present for the preparation of monocyclic 1,2,3-triazines, and both the generality and validity of the procedure have been established. Thus, a substantial number of derivatives of the type 2, R = alkyl, aryl, have now been prepared, and X-ray crystallographic analysis has confirmed the structures of the products (see Section II, D, 2). Thermolysis of triarylcyclopropenyl... 

Aminonaphthalene (775) reacts with diethyl azodicarboxylate to give the trisubstituted hydrazine (776) which can be cyclized in wet piperidine to l,4-dihydro-3-oxonaphtho-[2,1 -e][ 1,2,4]triazine-1 -carboxylate (777) (21CB213). 

Formaldehyde reacts with amines to yield the 1,3,5-trisubstituted hexahydro-1,3,5-triazines and with nitriles to form the acyl derivatives (Scheme 90) (59HC(13)1, p. 486, B-61MI22000, p. 658). Hexamethylenetetramine (70) is prepared by heating an ammoniacal solution of formaldehyde (B-61MI22000, p. 688). 

Most of the commercial triazine pesticides are trisubstituted 1,3,5-triazines of the general structure... 

By analogy with 4- and 2-chloropyrimidines, it is reasonable to predict the relation 5-as-triazinyl > 3-os-triazinyl. The substantial activation by additional ring-nitrogens, especially in the optimal 1,3,6 arrangement, is evident in the fact that chloro-s-triaasines, even when deactivated by one or two substituents, are equally or more reactive than many chloro-azines or chloro-diazines. For example, 2,4,6-trichloro-s-triazine reacts with various nucleophiles to give monosubstituted derivatives at 0-10°, disubstituted at 20-30°, and trisubstituted at... 

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