Synthesis of 2-alkylpyrazole-1-oxides: A facile access to 1-alkyl-5-halopyrazoles

Selective N-alkylation of 1-hydroxypyrazole 1 into the corresponding 2-alky l-pyrazole-1-oxides 2a-f has been achieved by treatment with alkyl bromides in the absence of base. Subsequent deoxygenation/halogenation into 1-alkyl -5-halopyrazoles 3a-d and 4a-d using phosphorus oxyhalides is described.