Synthesis of 5-Substituted 1-Hydroxypyrazoles through Directed Lithiation of 1-(Benzyloxy)pyrazole

Article abstract of DOI:10.1021/jo00121a017

1-Hydroxypyrazoles have been converted to 1-(benzyloxy), <(9-phenylfluorenyl)oxy>, <(N,N-diethylcarbamoyl)oxy>, and (silyloxy)pyrazoles. 1-(Benzyloxy)pyrazole was lithiated selectively in the 5-position.Subsequent reaction with electrophiles gives rise to 1-(benzyloxy)pyrazole with carbon, halogen, silicon, sulfur, or tin substituents at the 5-position. 1-(Benzyloxy)pyrazoles could be debenzylated by hydrogen bromide or hydrogenolysis producing 5-substituted 1-hydroxypyrazoles in high overall yield.