Spontaneous Cyclization of 2‐Methylthiosemicarbazones Yields New 1,2,4‐Triazolidine‐3‐thiones, Useful as Building Blocks for Drug Design

Abstract From the point of view of medicinal chemistry, thiosemicarbazones are interesting molecules as they exhibit various biological activities, such as antitumor, antifungal, antibacterial, antiviral, and antileukemic properties, and their synthesis is deeply investigated. However, the synthesis using 2‐methylthiosemicarbazide as a starting compound to prepare new 1,2,4‐triazolidine‐3‐thione compounds via 2‐methylthiosemicarbazone cyclization has not been reported yet. Therefore, fifteen new 1,2,4‐triazolidine‐3‐thione compounds were synthesized during a cyclization reaction using a simple green procedure with minimal use of hazardous solvents. The synthesized compounds were characterized with the techniques of NMR, IR, MS, and CHN elemental analysis. In addition, the structure of 11 of these compounds was confirmed by X‐ray structure determination. Selected compounds were subjected to cytotoxicity assay and microbiological tests for antimicrobial susceptibility and quorum sensing inhibition and tested for their inhibitory effect on the metalloenzyme NDM‐1, which causes antimicrobial resistance.