4-Aminotriazole, diazotization

An interesting example of how the reaction conditions can influence the structure of the product is shown in Scheme 2-10. Depending on the acidity of the reaction medium and on the reaction time, the diazotization of aminotriazoles (2.18) yields the nitrosoamines (2.19), the chloro compounds (2.20), or the azo coupling products i.e., the triazenes (2.21), as shown by Gehlen and Dost (1963). 

A special approach to [l,2,4]triazolo[3,2-c][l,2,4]triazine derivatives is the transformation of 3-diazo[l,2,4]triazoles, easily available by diazotation of aminotriazoles. These compounds already contain the five nitrogen atoms in the correct sequence in order to form the desired bicyclic ring system and, thus, their reaction with proper bifunctional reagents can give rise the cyclized products in one single step. Such transformations are collected in Scheme 50. 

Displacement of nitrogen from diazonium salts derived from 4- or 5-aminotriazoles can be achieved in the same manner as for other aromatic diazonium salts for example, diazotization of 4-amino-triazole-5-carboxamide and reaction with iodine and potassium iodide gives the 4-iodo derivative. ... 

Amino-l,5-diphenyltriazole is deaminated by diazotization in ethanolic solution and warming. 1-Aminotriazoles are deaminated in high yield by treatment with nitrous acid. Removal of a toluene-p-sulfonamido group can be accomplished in two steps by acid hydrolysis followed by diazotization, or in one step by treatment of the 1-toluene-p-sulfonamide derivative with sodium in liquid ammonia. ... 

Amino-l,2,4-triazole was alkylated with 4-nitrobenzyl bromide by simply refluxing the mixture in isopropanol to give SO in excellent yield. The aminotriazole SO was deaminated with NaNOa in aqueous HCI and the nitro group was reduced with ammonium formate catalyzed by 10% Pd/C to deliver 47 in an improved yield over the route shown in Scheme 17. Diazotization of 47, reduction of the diazonium salt with sodium sulphite and Fischer indolization of the resulting hydrazine with 4-( /, /-dimethylamino)butanol dimethyl acetal was performed in a single step to afford rizatriptan (4) in 45% yield. 

Amino-5-methyltriazole and carbethoxy isothiocyanate, stirred in acetonitrile, gave 3-methyl-5-thioxo-l,2,3-triazolo[l,5-a][l,3,5]triazin-7-pne (104) (25°C, 30 min, 65%) (76JHC589). 5-Phenyltriazole-4-diazonium chloride and phenyl isocyanate, stirred in dichloromethane, provided 3,6-diphenyl-l,2,3-triazolo[5,l-d][l,2,3,5]tetrazine-4-one (105) (25°C, 41%) (79TL4253). Finally, diazotized 4-aminotriazole was coupled to 2-naphthol. The product, refluxed in methanol, was cyclized to naphtho[2,l-e][l,2,3]-triazolo[l,5-h] triazine (106) (2 days, 80%) (74JHC867). 

There is strong evidence that 5,6-didehydrobenzimidazoles (591) have been generated by both oxidation of the aminotriazoles (592) (Section II.l.D) and aprotic diazotization of the amino acid 593 (Section II.l.C). The intermediate diazonium carboxylate 594 from the latter precursor proved to be remarkably stable but finally gave a low yield of the tetracyclone adduct 595b upon thermolysis. Oxidation of (592) led to much better yields of the expected aryne... 

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