Haloacetylated enol ethers. 2. Synthesis of 5‐trifluoromethylpyrazoles

Abstract 1‐Methyl‐5‐(trifluoromethyl)‐1 H ‐pyrazoles 2, 3 and 4,5‐dihydro‐1‐phenyl‐5‐(trifluoromethyl)‐1 H ‐pyrazol‐5‐ol 4 were prepared by reaction of 4‐alkoxy‐1,1,1‐trifluoro‐3‐alken‐2‐ones 1 and hydrazine, methylhydrazine, and phenylhydrazine, respectively, in good yields. Compound 1 proved to be a versatile building block for the regiospecific construction of pyrazole rings having an 5‐trifluoromethyl substituent.