A convenient conversion of pyrazolyl disulfide to sulfides by sodium dithionite and synthesis of sulfoxides

Indirectly introduce trifluoromethylthio-, alkylthio-, and trifluoromethylsulfinyl to pyrazole ring by a convenient reaction of a pyrazolyl disulfide with F3CBr and alkyl halides in the presence of sodium dithionite at room temperature. Followed by selective oxidation with H2O2 or trichloroisocyanuric acid (TCCA) to give trifluoromethylsulfenyl phenylpyrazole, alkylsulfenyl phenylpyazole, trifluoromethylsulfinyl phenylpyrazole 4a (a highly efficient insecticide named fipronil) and ethylsulfinyl phenylpyrazole 4c derivatives, respectively.

A novel, convenient transformation of a pyrazolyl disulfide to sulfides with alkyl halides in the presence of sodium dithionite at room temperature, and a one-pot procedure of oxidizing sulfides to sulfoxides was described. Figure optionsDownload as PowerPoint slide