A one-pot approach for the direct synthesis of substituted pyrazoles from isoxazoles is reported. The process involves isoxazole N–O bond cleavage mediated by a molybdenum complex, in situ hydrolysis of the resulting β-amino enone to the corresponding 1,3-diketone, followed by pyrazole formation in the presence of hydrazine or substituted hydrazine. Good to excellent yields and regioselectivities are obtained with nonsymmetric isoxazoles. By using readily available starting materials, a wide range of substituted pyrazoles may be synthesized by this method.
