Selectively Oxidative Thiolysis of Nitriles into Primary Thioamides and Insecticidal Application

Primary thioamides are useful building blocks for drug and insecticide development, therefore an environmentally benign synthesis of primary thioamides is desired. This paper discloses an oxidative thiolysis for the selective transformation of nitriles into primary thioamides using elemental sulfur or thiuram in the presence of K(2)S(2)O(8)in DMF/H2O. This practical method enables access to a wide range of synthetically and pharmaceutically useful primary thioamides. Advantages of this reaction include transition-metal-free and base-free reaction conditions, use of an environmentally benign solvent (DMF/H2O) system, the use of non-toxic elemental sulfur or thiuram as the sulfur sources, and good functional groups tolerances with excellent selectivity. Furthermore, the insecticide Fipronil can also be converted to the corresponding thioamide and maintains excellent bioactivity againstP. xylostella. The LC(50)value of Fipronil thioamide is 1.25 mg/L.