1,2,3-Triazine, tris formation, reactions

A special type of modification of substituents bound to the 1,2,4-triazine nucleus is the formation of condensed 1,2,4-triazines, such as formation of imidazo[4,5-c]-l,2,4-triazines 21 by reaction of 1,2,4-triazine-5,6-diamines with ortho esters 103-189 with glyoxal or substituted glyoxals dihydro- and tetrahydropyrazino[2,3-e]-l, 2,4-triazines 22 are obtained. Pyrazino[2,3-e]-1,2,4-triazine 23 is synthesized by dehydration of the tetrahydropyrazino[2,3-< ]-l,2,4-tri-azine.293-297-301... 

From liquid-phase hydrogenation studies56, we can derive the enthalpy of formation of the perhydro-tris[l,2-a 3,4-c 5,6-e]pyrrolo-l,3,5-triazine and of perhydro-tris[l,2-a 3,4-c 5,6-e]pyrido-l,3,5-triazine (35 with n = 5 and 6, respectively). Correcting for medium effects in directly measured enthalpies of solution, hydrogenolysis reaction 43... 

Kinetic studies of the reaction of a CH2S(CH2)3SCH2-linked bis-terpyridyl ligand (bterpy) with [Fe(terpy)2] revealed a very slow two-step process. The mechanism suggested consists of slow loss of one terpy, rapid formation of [Fe(terpy)(bterpy)], and finally slow displacement of the second terpy as the partially bonded bterpy becomes hexadentate. " Replacement of the 2,4,6-tri(2 -pyridyl)-l,3,5-triazine, 2,4,6-tptz (66), in [Fe(2,4,6-tptz)2] " " by phen or bipy is alleged to occur by an associative mechanism. ... 

Analogous reactions with perfluoro(isopropyl-l,3,5-triazine) and per-fluoro(diisopropyI-l,3,5-triazine) with CsF yielded adducts 116 and 117, respectively, which were detected by 19F-NMR. Use of potassium fluoride, either alone or associated with 18-crown-6, did not lead to the formation of the adducts. In contrast, from tris(perfluoroisopropyl)-l,3,5-triazine no adduct was detected. This is quite interesting because it would indicate the importance of the gem-difluoro substitution to stabilize the adduct,160 in analogy with the effect of gem-dimethoxy substitution.76... 

Reaction of Cytochrome cIinn with Bis(ferrozine)copper(II) Knowledge of the redox properties of cytochrome c was an encouragement to initiate a kinetics investigation of the reduction of an unusual copper(II) complex species by cyt c11. Ferrozine (5,6-bis(4-sulphonatophenyl)-3-(2-pyridyl)-1,2.4-triazine)286 (see Scheme 7.1), a ligand that had come to prominence as a sensitive spectrophotometric probe for the presence of aqua-Fe(II),19c,287 forms a bis complex with Cu(II) that is square pyramidal, with a water molecule in a fifth axial position, whereas the bis-ferrozine complex of Cu(I) is tetrahedral.286 These geometries are based primarily upon analysis of the UV/visible spectrum. Both complexes are anionic, as for the tris-oxalato complex of cobalt in reaction with cytochrome c (Section 7.3.3.4), the expectation is that the two partners will bind sufficiently strongly in the precursor complex to allow separation of the precursor formation constant from the electron transfer rate constant, from the empirical kinetic data. 

Sanders and coworkers have shown that the interaction between pyridine and Zn-porphyrins can be used for controlling the outcome of the Glaser coupling of 62. They were able to show that ethynylphenyl-substituted Zn-porphyrins can be cyclodimerized or cyclotrimerized, depending on the specific pyridyl template present in the reaction medium [28], With 4,4 -bipyridene (63), the cyclodimer 64 was obtained in 70% yield, whereas the presence of 1,3,5 -tris (4-pyridyl) -triazine (65) supports the formation of the cyclotrimer 66 (50%) (Scheme 6.10). 

Formation of 1,3,5-triazine derivatives has also been observed in the reaction of 3-halo-5-phenyl-1,2,4-triazines with potassium amide in liquid ammonia (80JOC881) and on treatment of 3-chloro-5,6-diphenyl-l,2,4-tri-azine with phenylmagnesium bromide (83IJC(B)559). Both transformations were assumed to be initiated by the addition of the nucleophile employed at C-5 of the 1,2,4-triazine ring. 

New 2-aryl-l,2,4-triazin-3-ones and 2-aryl-l,2,4-tri-azepin-3-ones were prepared in a three step reaction sequence from readily available aryl isocyanates and aminoacetals or ketals. The key step in the reaction scheme was the formation of 2-arylsemicarbazides by the treatment of arylureas with the aminating reagent 0-(4-nitrophenyl)hydroxylamine. 2-Aryl-1,2,4-triazin-3-ones... 

A number of 1,2,4-triazines can be lithiated, such as 5-methoxy-l,2,4-triazines 18, 1,2,4-tri-azine-6-carboxamides or 1,2,4-triazine 4-oxides and the thus formed lithio-l,2,4-triazines reacted with electrophiles. This reaction method has been used to introduce the following substituents into the 6-position iodo, carbaldehyde, hydroxyalkyl groups. The reaction of 5-lithio-l,2,4-triazines with electrophiles results in the formation of dimers and no substitution products are formed.44,2 9... 

In contrast to alkyl cyanates, alkyl thiocyanates trimerize to provide the 2,4,6-tris(alkylsul-fanyl)-l,3,5-triazines 21 without notable formation of the corresponding isothiocyanu-rates.265 -267,481 In general, the reaction is acid catalyzed to prevent isomerization of the starting alkyl thiocyanate to the corresponding alkyl iso thiocyanate. 

Triethyl l,3,5-triazine-2,4,6-tricarboxylate and 2,4,6-tris(methylsulfanyl)-1,3,5-triazine react in an inverse electron demand Diels-Alder reaction with several electron-rich dienophiles.6 The tricarboxylate 9 (R1 = C02Et) undergoes a well-defined [4 + 2] cycloaddition reaction with ynamines and enamines. In the case of ynamines, the [4 -1- 2] cycloaddition is followed by a retro Diels - Alder reaction at 40 100 °C with direct formation of the substituted pyrimidines 11. In the case of enamines, the cycloaddition provides stable, isolable [4 + 2] adducts 12. The subsequent retro Diels-Alder reaction and the final aromatization step is catalyzed by a mixture of hydrochloric acid and dioxane, anhydrous p-toluencsulfonic acid or acetic acid. This two-step process can be reduced to a single operation by conducting the reaction in a solution of dichloromethane and acetic acid at 40-100 °C.6 Electron-deficient dienophiles like dimethyl acetylenedicarboxylate or 1,4-naphthoquinone do not react with this triazine. 

Heating of 3-[3-(l-indolyl)propyl]-l,2,4-triazines 173 in tri(isopropyl)benzene, DMF, or use of microwave activation in the inverse electron demand Diels-Alder reaction results in the formation of fused derivatives 174 (Scheme 108) <2003TL4495, 2004JOC7171>. 

The pH-dependent NMR spectrum of [Ru(bipy)2(py)2] salts has been shown not to involve the formation of covalent hydrates. The reaction of 2,4,6-tris(2-pyridyl)-l,3,5-triazine (46) with aqueous copper(I) salts results in a metal-promoted hydrolysis to yield complexes of 2-pyridinecarboxamide and (47). A number of metal complexes have been characterized structurally from these reactions. 

Incorporation of perfluoroisopropyl groups into trifluoro-l,2,4-triazine takes place smoothly in the reaction of 18 with hexafluoropropene and cesium fluoride without of any solvent [12], When the reaction is carried out at 125 °C for 25 min amixture of 5-perfluoroisopropyl-derivative 100 and 3,5-di- and 3,5,6-tri (perfluoroisopropyl)-1,2,4-triazines 101,102 are formed (Scheme 43), while the formation of tiisubstituted derivative 102 (yield 52 %) takes place on heating at 110 °C for 2 h. 

In a similar manner, the reaction of cyanuric fluoride 55 with tris(trimethylstannyl) amine in dry ether at 0 °C leads to the formation of 2,4-difluoro-6-[di(trimethylstannyl)]-amino-l,3,5-triazine 131 (Scheme 52) [5],... 

Tris(o-hydroxyphenyl)triazine possesses structural features similar to 8-hydroxyquinoline. Linear polymers can be prepared by reaction of this trifunctional ligand with divalent metal salts in solution (32, 34). Reaction in bulk leads to the formation of cross-linked network polymers. Exactly how the difference in polymer structures [31] and [32] was determined was not made clear because both products were insoluble and infusible. It was postulated that the linear structure was obtainable because it precipitated from the reaction solvent before reaction with a third metal ion. Dimethylformamide was used in conjunction with an alcohol, such as methanol or ethanol, for the solution reaction. Temperatures up to 330°C were used for the bulk reaction. 

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