1- Substituted 1,2,3-triazoles, metallation oxidation

Bromine at C5 of 2-substituted 1,2,3-triazole 1-oxides 361 is readily removed without touching the N-oxygen by treatment with aqueous-methanolic Na2S03 (2010UP2). Debromination has also been achieved by metallation followed by protonation as described in Section 4.1.6.4 (Scheme 109). 

The anions generated by proton-metal or halogen-metal exchange (Section 4.1.6.3-4) reacted readily with electrophiles like MeOD, Mel, I2, and A/-formyI morphol i ne (NFM) to give the 5-substituted 1,2,3-triazole 1-oxides 372 (2010UP2) (Scheme 112). 

Substituted 1,2,3-triazole 1-oxides 448 have been reported to undergo electrophilic and nucleophilic aromatic substitution and are subject to debromination, proton-metal exchange, and halogen-metal exchange followed by electrophilic addition. Transmetallation and cross-coupling have not been described. 3-Substituted 1,2,3-triazole 1-oxides 448 can be proton-ated or alkylated at the O-atom and they can be deoxygenated and deal-kylated. The individual reactions are described in Section 4.2.7.1-4.2.7.14. 

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