Synthesis and 13C NMR of (Trifluoromethyl)hydroxypyrazoles.

TLDR: In this article, the reaction of ethyl 4,4,4 trifluoroacetoacetate with methylhydrazine produced not only the previously reported 5-hydroxy-3-(trifluoromethyl)pyrazole 1 but also its unknown isomer the 3-hydrox-5-(trifioromethsyl) pyrazole 4. The structure assignements were established based on 13 C NMR spectra.

Abstract: Reaction of ethyl 4,4,4-trifluoroacetoacetate with methylhydrazine produced not only the previously reported 5-hydroxy-3-(trifluoromethyl)pyrazole 1 but also its unknown isomer the 3-hydroxy-5-(trifluoromethyl)pyrazole 4. The structure assignements are etablished based on 13 C NMR spectra. Compound 1 was converted to 5-chloro-3-(trifluoromethyl)pyrazolecarboxylic acid 3 in two steps.