A new approach for the synthesis of α‐ketothioamides from methyl ketone, pyrrolidine/piperidine and elemental sulfur using recyclable magnetic catalyst

Abstract

AbstractBACKGROUNDα‐Ketothioamides play a vital role in the fields of medicine and biology. There are many α‐ketothioamide synthesis pathways, but in general, most current methods involve either conventional heating in solvent conditions or using non‐recyclable catalysts. Thus, our work investigated the preparation of α‐ketothioamides under solvent‐free sonication using magnetic nanoparticle‐immobilized chlorozincate ionic liquid as a catalyst. The desired products were purified by chromatography columns and characterized using 1H NMR and 13C NMR.RESULTSIn this study, Lewis acidic ionic liquid grafted onto magnetic nanoparticles (Fe3O4@IL‐ZnCl2) was used as an effective heterogeneous catalyst for the generation of a variety of α‐ketothioamide derivatives. The optimized conditions were methyl ketone (1.0 mmol), amine (1.2 mmol), S8 (1.2 mmol) and Fe3O4@IL‐ZnCl2 (15 mg) under solvent‐free sonication at 80 °C for 5 h, and the crude products were obtained in a 34–94% isolated yield. Then, this procedure was successfully applied to a wide range of aryl and alkyl ketone compounds. Besides, there was only a slight loss in catalytic activity in three consecutive cycles, indicating the reusability and stability of the catalytic system.CONCLUSIONSWe have successfully designed a novel protocol for the generation of α‐ketothioamide derivatives from aryl/alkyl methyl ketones, amines, and elemental sulfur catalyzed by chlorozincate ionic liquid‐coated magnetic Fe3O4 nanoparticles. The reaction proceeded via a mild, efficient, solvent‐free sonication accompanied by a well‐reactive catalyst, which is easily separated and reusable. Besides, a feasible mechanism is presented. © 2023 Society of Chemical Industry.