An efficient preparation of novel 5-fluoropyrazolin-3-one derivatives from α-trifluoromethylated α-arylacetates

The reactions of α-trifluoromethylated α-arylacetates with 3 equiv of hydrazine, methylhydrazine or benzylhydrazine in 1,4-dioxane at reflux for 24 h afforded the corresponding 5-fluoropyrazolin-3-one derivatives in high yields. Similarly, treatment of with 3 equiv of PhNLiNH2 in THF at −78 °C, followed by warming to room temperature, resulted in the formation of in high yields.