1.3.5- Triazine methoxy derivatives

The pyrimidine compounds are known to undergo a rearrangement of the 0-alkyl derivatives to the iV-alkyl ones. The methoxy derivatives of 1,3,5-triazine display a similar behavior. On applying methyl iodide to 2,4-dimethoxy-l,3,5-triazine one of the methyl groups is shifted giving rise to l-methyl-4-methoxy-derivative (22). This compound was also obtained by methylation of 4-methoxy-2-oxo-1,2-dihydro-1,3,5-triazine (18) with diazomethane. At higher temperature (100°C) in presence of methyl iodide a shift of both methyl groups takes place and methiodide is formed simultaneously (23). Similarly,... 

Ring closure of 2-oxohydrazones 5a and 5b in refluxing dioxane occurs through an unusual intramolecular nucleophilic attack of the semicarbazide amino group to the keto function. The resulting 1,2,4-triazine carboxylates 6a (unequivocally assigned by X-ray analysis) and 6b provide 5-methoxy derivatives 7a and 7b upon reflux in methanol <00JOC2820>. 

Another example of a nucleophilic addition at C-3 is provided by the reaction of the quaternary salt 20 with sodium methoxide yielding the relatively stable adduct 33, (Scheme 24) (74BSF999). The C-3 adducts 35 and 36 have been suggested as intermediates in the conversion of 2-meth-yl-3-methylthio-l,2,4-triazin-5-ones 34 into the corresponding 3-methoxy derivatives however, no spectroscopic evidence for adduct formation has been presented (Scheme 24) (72BSF1511). 

Most of the triazines are derivatives of the symmetrical 1,3,5-triaz-ine-2,4-diamine, but other possibilities also exist. In position 6 there is a methylthio (the -tryns), a methoxy (the -tons), or a chloro group (the -azines). 

J. Keck, M. Roessler, C. Schroeder, G.J. Stueber, F. Waiblinger, M. Stein, D. LeGourrierec, H.E.A. Kramer, H. Hoier, S. Henkel, P. Fischer, H. Port, T. Hirsch, G. Rytz, and P. Hayoz, Ultraviolet Absorbers of the 2-(2-hydroxyaryl)-l,3,5-triazine class and their methoxy derivatives fluorescence spectroscopy and X-ray structure analysis, J. Phys. Chem. B 1998, 102, 6975-6985. 

Millet and woody crop plants tolerate terbuthylazine and sebuthylazine. The methylmercapto and methoxy derivatives of terbuthylazine (terbuthyrene, or Caragard , Geigy) and the methoxy derivative of sebuthylazine (Etazin , Geigy) are special selective herbicides. From the standpoint of residual effect, these three triazine derivatives are highly persistent herbicides. After a dosage of 10 kg/ha, crop plants sensitive to triazines (particularly cereals) cannot be sown for several years. 

The alkoxy triazines, of which only the methoxy derivatives have found practical use, are also compounds with high herbicidal activity. By the exchange of the chlorine atom for an alkoxy group, compounds with a water-solubility higher by... 

When the 5-methoxy derivative 107 was reacted with enamine in refluxing chloroform, pyridine 108 was obtained (Scheme 45) [28], Diels-Alder reaction of triazine 5 with norbomadiene leads to formation of pyridine 109 (Scheme 45). Low yield of 109 clearly shows that this Diels-Alder reaction proceeds in an inverse electron demand manner [28]. 

Because of the similarity of the substituent effects in s-triazine and quinoline derivatives, it seems probable that in the former sequence hydrogen falls between the chlorine atom and the methoxy group. 

Derivatives of 3-oxo-l,2,4-triazine 1-oxide undergo alkylation with various alkylating agents. Thus the reaction of 3-methoxy-l,2,4-triazine 1-oxide 20 with 2,3,5-tii-(9-benzoyl-/3-D-ribofuranosyl bromide, followed by the removal of the benzoyl protection with sodium methoxide, leads to an abnormal nucleoside 4-(/3-D-iibofuranosyl)-l,2,4-triazin-3(4//)-one 1-oxide 21 (73JOC3277). 

A number of 1,2,4-triazines such as the parent compound, the 3-methylthio, 3-methoxy and 3-amino-6-bromo derivatives add ammonia in liquid ammonia at -44 °C to the N(4) —C(5) bond to give adducts of type (lOl), as was shown by XH and 13CNMR spectroscopy. No reaction was observed with 3-methoxy-l,2,4-triazine 1-oxide (71), other 3-amino-l,2,4-triazines, or compounds with a substituent in the 5-position. As was shown using lsN-enriched ammonia, an equilibrium between the covalent addition products (101) and the open-chain isomers (102) does not occur (78RTC273). 

Triazine and some of its 3-methoxy, 3-methylthio or 3-amino derivatives (103) with the 5-position unsubstituted react with potassium cyanide to afford two products, the i-triazinyls (105) and the l,2,4-triazine-5-carboxamides (104). These are proposed to be formed via a cyanide adduct (73JHC343, 74JHC43). The bi-l,2,4-triazinyls (105) were also isolated when the triazines (103) were treated with sodium methoxide or potassium in liquid ammonia. It is suggested that the methoxide-catalyzed dimerization proceeds via an anionic intermediate (106), while the reaction with potassium in liquid ammonia occurs via a free radical process. 

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