PREPARATION OF 3(5)-PHENYL-1-HYDROXYPYRAZOLE 2-OXIDE AND 4-METHYL-3(5)-PHENYL-1-HYDROXYPYRAZOLE 2-OXIDE

Nitrosation of acrylophenone oxime or of methacrylophenone oxime with n-butyl nitrite in the presence of pyridine and copper(II) sulfate gives the copper complexes of the title compounds. The free 1-hydroxypyrazole 2-oxides are isolated by treating the copper complexes with dilute sodium hydroxide, filtration, and acidification of the basic filtrates. The title compounds are the first examples of 1-hydroxypyrazole 2-oxides in which the C3(5) ring position is unsubstituted.