2- Hydroxypyrazole 1-oxides preparation

Substituted pyrazole 1-oxides 74 can be prepared by N-oxidation of 1-substituted pyrazoles 89, by A/-alkylation of 1 -hydroxypyrazoles 90, or by cyclization of 1,3-oximimines, conjugated oximenamines, or conjugated 1,3-nitrosoimines. 

The synthesis of pyrazolines and pyrazoles by a [CCNN + C] process has not made significant advances since <84CHEC-I(5)167>. A new method to prepare 1-hydroxypyrazole 2-oxides by nitro-sation of acrylophenone oxime, [CCCN + A] has been reported <93JHCl 163>. 

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