Preparation of 1-Hydroxypyrazoles and 1-Hydroxy-1,2,3-triazoles by Dealkylation of Pyrazole and Triazole N-Oxides.
作者:Mikael Begtrup、Per Vedsø、Ingrid Hegbom、Eli Ranes、Bente Nielsen、Ruby I. Nielsen、Carl Erik Olsen、Connie N. Rosendahl、Monika Haugg、Nathalie Trabesinger-Rüf、Elmar G. Weinhold
DOI:10.3891/acta.chem.scand.50-0549
日期:——
1-Hydroxypyrazoles were obtained from 2-benzylpyrazole I-oxides by debenzylation with iodotrimethylsilane. 1-Hydroxy-1,2,3-triazoles were achieved from 2-benzyltriazole 1-oxides by debenzylation effected with cone. hydrobromic acid or from 2- or 3-p-methoxybenzyltriazole 1-oxides by de-p-methoxybenzylation accomplished by treatment with cone. sulfuric acid. 1-Methoxy-1,2,3-triazole was obtained by de-p-methoxybenzylation of 1-methoxy-3-p-methoxybenzyl-1,2,3-triazolium tetrafluoroborate accomplished by treatment with cone. sulfuric acid. 1-Hydroxypyrazole was selectively N-benzylated in absence of base to give 2-benzylpyrazole 1-oxide which, upon selective substitution at the 3-position and subsequent debenzylation, produced 3-substituted 1-hydroxypyrazole.