Reactions of Trifluoroacetonitrile Oxide or -nitrilimines with β-Diketones and β-Keto Esters

N-Phenyl-C-(trifluoromethyI)nitrilimine cyclized with β-diketones or β-keto esters under alkaline conditions to give the corresponding 3-trifluoromethylpyrazoles with acyl or alkoxycarbonyl group at the 4-position of the ring, respectively. While trifluoroacetonitrile oxide with β-diketones provided the corresponding trifluoromethylisoxazoles, its reactions with β-keto esters gave 4-acyl-5-hydroxy-3-trifluoromethylisoxazoles as well as the expected isoxazoles without the regioselectivity.