The Synthesis of Fipronil Derivatives via Pd‐Catalyzed Direct Alkynylation of Phenylpyrazole with Terminal Alkynes in Green Solvents

Abstract

The palladium‐catalyzed direct alkynylation of phenylpyrazole (5‐amino‐1‐[2, 6‐dichloro‐4‐trifluoromethylphenyl]‐lH‐pyrazole‐3‐carbonitrile) with terminal alkynes is being reported. The protocol utilizes EtOH/H2O as the solvents and does not require the preactivation of phenylpyrazole with halide to form its halide substrate, which exemplifies the ideal condition of green chemistry. Various terminal alkynes such as arylacetylenes and aliphatic alkynes are used in the reaction to afford a series of fipronil derivatives of 4‐alkynyl‐1‐phenylpyrazoles with potential bioactivity in good yields. All the compounds were characterized by 1H NMR, 13C NMR, and HRMS spectroscopic techniques.