Preparation of N-hydroxyazoles by oxidation of azoles

Azoles without N-substituents are oxidized with per-acids or perborate to the corresponding N-hydroxy substituted azoles. 1,2,4-Triazole and tetrazole produce two isomers separated through their O-benzyl derivatives. Imidazole and 1,2,3- and 1,2,4-triazole can be di-oxygenated in low yields. N-Hydroxypyrazole is deoxygenated by per-acid.