Other Electrophilic Attack at Nitrogen

Direct amination of benzo[l,2- / 4,5-if]bistriazole (178) in aqueous base with hydroxylamine-0-sulfonic acid gives a mixture of three diamino derivatives and two monoamino derivatives (Equation (15)). The combined yields of diamino and monoamino products are 45% and 48%, respectively. The three diamino derivatives can be separated by fractional crystallization from ethanol 86JOC979 . A-Amination of triazoles can also be achieved by treatment with NaH in DMF followed by O-amino-2,4-dinitrophenol 85TL335 or 0-(mesitylsulfonyl)hydroxyamine (9lJCS(Pl)2045 . 

1-Substituted 1,2,3-triazoles are oxidized by w-chloroperoxybenzoic acid at the more basic N(3) to give the corresponding triazole A -oxides. The yield is lower if an electron-withdrawing substituent is present at the C(4) or C(5) position 87ACS(B)724 . 2-Alkyl-1,2,3-triazole-1-oxides are produced from the oxidative cyclization of alkyl hydrazono oximes 86ACS(B)262 see Section 4.01.8.1. 

Triazoles can be activated towards electrophiles by the introduction of an A-oxide group. N-Oxidation gives rise to better activation of the 5-position than the 4-position. Thus, bromination of 3-benzyl-1,2,3-triazole 1-oxide (192, R = PhCH2) requires only 120 h at 20 °C and affords the 5-bromo compound (193) in quantitative yield 87ACS(B)724 . 3-Phenyl-1,2,3-triazole 1-oxide is 

6 -Trinitrophenyl)-l,2,3-triazole undergoes nitration at the 4-position. The 1-isomer does 

2- methyl-4-nitrotriazole to 2-methyl-4,5-dinitrotriazole which is thermally stable above its melting point 86ACS(B)262 . Nitration of benzotriazole by mixed acid gives 4-nitrobenzotriazole, while 5-methylbenzotriazole affords 5-methyl-4-nitrobenzotriazole 92JOC190 . 

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