Triazoles 1.4- substituted

In a 1-substituted 1,2,3-triazole (79), both the 2- and 3-nitrogen atoms possess lone pairs of electrons that are available for quaternary salt formation, and quatemization is known to occur at the 3-nitrogen atom to give the symmetrical cation (80). Thus, the reaction between 1-methyl-l,2,3-triazole and benzyl iodide yields the same salt as is obtained from the interaction of 1-benzyl-1,2,3-triazole and methyl iodide the salt must therefore be 80 (R = Me, R = PhCH2,... 

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. 

The C(5) position of 1-substituted 1,2,3-triazoles is activated towards nucleophilic attack by a pyridine-like nitrogen, and the equivalent C(4) and C(5) positions of 2-substituted 1,2,3-triazoles are weakly activated. However, a suitable leaving group, such as a halogen, is generally required for nucleophilic substitution <88BSB573>. 

Substituted 1,2,3-triazoles undergo lithiation with n-butyllithium at —20 to — 60 °C and reaction... 

Triazoles (see Section II). 1-Substituted 1,2,3-triazoles (64) readily undergo quaternization at N-3.171,172 Quantitative data are not available, but the fact that methyl fluorosulfonate is required to quaternize isomeric structures 65 suggests that they are much less reactive than 64.173 Since the two isomers show large differences in basicity,174 it seems likely that the large separation in reactivity is not primarily due to... 

Substituted 1,2,3-triazoles, 1,2,4-triazoles and tetrazoles are metallated by n-butyllithium at low temperature at the 5-position. At room temperature 5-lithium derivatives tend to undergo ring opening. No direct lithiation of a 2-substituted 1,2,3-triazole has been reported. 

The aromatic 3-substituted 1,2,3-triazole 1-oxides 448 are derived from 1-substituted 1,2,3-triazoles 457 by appending an oxygen atom to the... 

Substituted 1,2,3-triazole 1-oxide 448 can be prepared by N-oxidation of 1-substituted 1,2,3-triazoles 457, by N-alkylation of 1-hydroxy-1,2,3-triazoles 443, by cyclization of triazene 1-oxides 460, or by rearrangement of 2-substituted 1,2,3-triazole 1-oxides 445 (R=PMB). Finally, base-mediated ring opening of pyrimidinediones 463 offers a route to 464. 

Substituted 1,2,3-triazoles 457 (R=Aik, Ar, or OH) are oxidized by 3-chlo-roperbenzoic acid in ethyl acetate solution to corresponding 3-substituted... 

Substituted 1,2,3-triazole 2-oxides 508 (Scheme 150) are only known as benzocondensed constructs 509, which are beyond the scope of the present review [1973JHC495] (Scheme 151). 

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