Synthesis and reaction of 5‐amino‐3‐trifluoromethylisoxazole and ‐pyrazole‐4‐carboxylic acids

Abstract 5‐Amino‐3‐trifluoromethylisoxazole‐ and ‐pyrazole‐4‐carboxylic acids were prepared by the reactions ot trifluoroacetonitrile oxide or ‐imines with cyanoacetic acid derivatives, respectively. The behavior of thus obtained aminoazole‐4‐carboxylic acids toward some electrophiles was examined. In acylation with acyl chlorides, the aminoisoxazole‐4‐carboxylate 2a was diacylated to give the (diacylamino)isoxazole‐4‐carboxylate 7, whereas the analogous aminopyrazole 5a produced the cyclized pyrazolooxazinone 13. Moreover, carbamoylation of 2a with isocyanates gave the trifluoromethylisoxazolouracils 10.