An ultrasound-based approach for the synthesis of indoles under Pd/C catalysis

Abstract

An ultrasound assisted method has been developed for the Pd-mediated synthesis of indole derivatives in good to acceptable yields. The methodology involved Pd/C-catalyzed coupling–cyclization of 2-iodosulfanilide with alkynes under ultrasound irradiation in the presence of LiCl and NaHCO3 in DMF. A variety of internal/terminal alkynes was employed in this CC followed by CN bond forming reaction to afford the corresponding indoles. Being faster and milder method the present ultrasound-based approach appeared to be a useful and cheaper alternative to the existing methods. Keywords: Ultrasound, Pd/C, Indole, Alkyne