Unveiling a Novel Mechanistic Pathway: Thiol and DMSO-Facilitated Synthesis of Pyrazole Amine Thioether

Abstract

The present protocol shows a novel and greener approach for synthesizing pyrazole amine thioether, employing thiophenol, 3-aminocrotononitrile, and phenylhydrazine hydrochloride. Notably, this methodology deviates from the literature report in making thioether derivatives using oxidant-free and room-temperature conditions. Based on the control experiments, it was found that the thioether link in the intermediate facilitated the 5-exo-dig cyclization reaction exclusively in the DMSO solvent. This is probably due to the nitrile group's activation by the structure's thioether moiety. The control experiment demonstrates the significance of the thioether compound in the reaction. Without any oxidizing agent, introducing thioether in any heterocyclic compound is not possible, as per the literature reports. Our reaction showed excellent tolerance by involving various phenylhydrazine hydrochloride and thiophenol compounds, allowing for the synthesis of various pyrazole amine thioether derivatives in good to excellent yields. The reaction follows the 5-exo-dig cyclization strategy.