Synthesis of Sulfur-Containing Trifluoromethyl-1H-pyrazoles from 4,4,4-Trifluoro-1-phenylbutane-1,3-dione

A three-component condensation of 4,4,4-trifluoro-1-phenylbutane-1,3-dione with formaldehyde and alkanethiols led to 2-[(alkylsulfanyl)methyl]-4,4,4-trifluoro-1-phenylbutane-1,3-diones, the heterocyclization of which with hydrazine, phenylhydrazine, or benzylhydrazine under heating or microwave irradiation afforded the corresponding 4-(alkylsulfanylmethyl)-substituted 3-(trifluoromethyl)-1H-pyrazoles. The reaction of sulfur-containing 4,4,4-trifluoro-1-phenylbutane-1,3-diones with phenyl- and benzylhydrazine was characterized by high regioselectivity and resulted in the predominant formation of 1-aryl-5-phenyl-3-(trifluoromethyl)-1H-pyrazoles. 2-[(Alkylsulfanyl)methyl]-4,4,4-trifluoro-1-phenylbutane-1,3-diones were unstable and underwent detrifluoroacetylation upon isolation by chromatography to form 3-(alkylsulfanyl)-1-phenylpropan-1-ones.