Novel two step synthesis of pyrazoles and isoxazoles from aryl methyl ketones

Various acetyl aromatics when reacted with dimethylformamide dimethyl acetal gave 1-aryl-3-dimethylamino-2-propen-1-ones. These intermediates are masked β-ketoaldehydes and react with hydrazine hydrate or hydroxylamine at room temperature to give in good yields pyrazoles or isoxazoles.