3-Substituted 1,2,3-triazole 1-oxides applications

The synthetic applications of substituted 1,2,3-triazole 1-oxides and 1,2,3-triazolium-l-imides in the preparations of 1,2,3-triazines, 1,3,4,5-oxo- and -thia-triazines, and 1,2,3,5-tetrazines have been discussed in Section 4.01.4.12. Conversions of 1,2,3-triazolines into aziridines either thermally or photochemically were described in detail in CHEC-I <84CHEC-1(5)691 > and in a review <84AHC(37)217>. Some recent developments are discussed in Section 4.01.5. 

Studies on the potential of the electrochemical approach to pyrazolotriazoles 117 showed that under the conditions of bicycle synthesis from 3-amino-4-hydrazonopyrazoles the N-l-unsubstituted triazole ring of 117 was further oxidized in a one-electron peak, followed by proton removal to yield the bis-(l,l )-2-phenylpyrazolo[3,4-i/][l,2,3]triazoles 118. This observation is significant, since in spite of pronounced pharmaceutical applications of pyrazoles, the redox characteristics of substituted pyrazoles have received limited attention (Scheme 13) <2001MI1022>. 

Deprotonation followed by addition of an electrophile, if needed combined with application of protecting groups, makes a great number of regi-oselectively substituted 1,2,3-triazole 1-oxides 448 accessible (Scheme 146). 

Substituted 1,2,3-triazole 1-oxides 448 have been used for and have a great potential for the synthesis of regioselectively substituted 1,2,3-triazoles 457 which possess their own virtues as mentioned in Section 4.1.7. However, no reports on the biological activity or on the application of 3-substituted 1,2,3-triazole 1-oxides 448 are available. The missing data may be due to the, until recently, lack of a simple synthesis of the 1-oxides 448 based on a direct cyclization. 

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