1.2.4- Triazines 6- amino- from

In a similar reaction, 2-(o-nitrophenyl)ethylamine (100) may be reduced in an ammonia buffer to the hydroxylamine and oxidized to the nitroso derivative, which condenses with the amino group to a dihydrocinnoline.160,161 It is also possible to prepare dihydrobenzo-l,2,3-triazinones on reduction of o-nitrobenzhydrazide, followed by oxidation of the hydroxylamine to a nitroso group, and 3-phenyldihydrobenzo-l,2,3-triazine (101) from N-phenyl-(V-(o-nitrobenzyl)hydrazine (100) in an analogous way161 [Eq. (78)]. 

The practical preparation of novel 2-(arylmethyl) amino-4-arylamine-6-alkyl-1,3,5-triazines (vi) from the microwave assisted reaction of easily accessible dicyanidiamide and arylamines has also been described [22]. 

The Wittig-type reactions of iminophosphoranes with isocyanates and related compounds have also been extensively used in heterocyclic synthesis. Examples include the preparations of the mesoionic [l,3,4]thiadiazolo[2,3-c][l,2,4]triazines (210) from (209), 0 bicyclic guanidines, e.g. (212), from (211), naphthypyridines (215), (216), and (217) from (213) and (214), 2 pyrido[l,2-f]pyrimido-[4,5-d)pyrimidines (218), 7H-pyrido-[4,3-c]- (219) and 10H-pyrido[3,4-b]- (220) carbazoles, tricyclic fused 2,4-diimino-l,3-diazetidines (222) from the bisiminophosphorane (221), benzotriazepines (225) from (223) and (224), 6 and mesoionic thiazolo-[2,3-b]-1,3,4-thiadiazoles (227) and N,N-bisheteroarylamines from the iminophosphorane (226), derived from 3-amino-4-phenylthiazole-2(3H)-thione. The carbodiimides (229), prepared from the iminophosphorane (228), can be converted into quinolines or a-carboline derivatives depending on the nature of the isocyanate used in the reaction with (228) and the reactions of iminophosphoranes (230) and (231) with aryl and styryl isocyanates provide one-pot syntheses of quinoline, a-carboline, and quinindoline derivatives. 9... 

Table 10 Yields of amino-1,2,4-triazines derived from the and Sn ° reactions...

Synthesis was accomplished of the s-triazine derivatives from uronic and polyuronic acids.5(R)-(2-Amino-4-di-methylamino-l,3,5-triazin-6-yl)-L-arabinopyranose and its methyl glucoside were prepared from gaiact-uronic acid. 5(R)-(2-amino-4-dimethylamino-l,3,5-triazin-6-yl)-p-d-xylo-pyranose was prepared from glucuronolactone. Methyl 5(R)-(2-Amino-4-di-methyl-amino-1,3,5-triazin-6-yl)-a-D-lyxopyranoside was prepared from mannuronolactone by ring closure with N,N-disubstituted biguanide. s-Triazine derivatives of polyuronic acids, such as pectin and alginic acid, were prepared similarly. 

A novel synthesis of nocardicins from hexahydro-2-triazines has been reported/ The strategy behind this synthesis lies in the expectation that treatment of hexahydro-s-triazines with a Lewis acid should give formaldimines which on reaction with an acid chloride would yield monocyclic jS-lactams. This was realized in practice with the hexahydro-s-triazines derived from a-amino-acids, e.g. Scheme 95. The 3-aminonocardicin nucleus is readily available by application of the usual deprotection procedures. 

In the triazinones, Ri is methyl or thiomethyl, R2 an amino group, and R3 a phenyl, alkyl or cycloalkyl group. Only three triazinones are available at present—metribuzin, metamitron, and the 5-triazine-2,4-dione, hexazinone. Log values are generally lower than for the triazines, ranging from 0 for hexazinone to 1.7 for metribuzin. 

Melamine. Melamine (cyanurotriamide, 2,4,6-ttiainino-j -triazine) C H N, is a white crystalline soHd, melting at approximately 350°C with vaporization, only slightly soluble in water. The commercial product, recrystallized grade, is at least 99% pure. Melamine was synthesized eady in the development of organic chemistry, but it remained of theoretical interest until it was found to be a usehil constituent of amino resins. Melamine was first made commercially from dicyandiamide [461-58-5] (see Cyanamides), but is now made from urea, a much cheaper starting material (9—12) (see also... 

Amino-4-anilino-s-triazine [537-17-7] M 168.2, m 235-236 , pKsst-5.5. Crystd from dioxane or 50% aqueous EtOH. 

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. ... 

Substances of this type have hitherto received little attention. One of the reasons appears to be the limited possibilities of preparation. The only known method of preparation, described by Woolley et ai./ proceeds from the derivatives of 4-aminoimidazole-5-carboxylic acid. The amide of this acid (142) is treated with nitrous acid to yield 4-hydroxyimidazo [4,5-d]-i -triazine (2-azahypoxanthine) (143), the amidine (144) yielding the 4-amino derivative (2-azaadenine) (145) under the same conditions. 2-Azahypoxanthine was probably obtained in the same way earlier but was not identified. ... 

When 5-methylthiosemicarbazide is used instead of amidrazone, 3-amino-1,2,4-triazine 4-oxides can be obtained. In this way 3-amino-5-methyl-6-phenyl-1,2,4-triazine 4-oxide 138 was synthesized from isonitrosopropiophenone [52CIL907, 89IJC(B)556]. 

The synthesis of 987 from 985 via 986 has been reported (83S759) by reaction of 985 with aryl isothiocyanates under neutral conditions. The reaction of 4-amino-6-anilino[l,2,4]triazine 988 with methyl iodide and then carbon disulfide gave 989 (90MI3, 90MI9). 

Most of the reported triazinothiadiazines have been prepared from 1,2,4-triazine derivatives. Treatment of amino-1,2,4-triazine 28 with chloroacetyl chloride in dioxane in the presence of triethylamine at 10 °C resulted in the formation of 6-methyl-4-(A -chloroacetamido)-3-thioxo-5-oxo-2,3,4,5-tetrahydro-l,2,4-triazine 29 and 3-methyl-4,7-dioxo-4,6,7,8-tetrahydro-l,2,4-triazino[3,4-A][l,3,4]thiadiazine 15 (Scheme 1) <2005JHC935>. 

Triazinothiadiazines 24 and 25 <2002IJH287> containing sydnone and coumarin systems have also been prepared from 4-amino-3-mercapto-6-substituted-l,2,4-triazin-5-ones 38 as shown in Scheme 5. 

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