An operationally simple and sustainable one-pot photo-oxidative formal [3 + 2] heterocyclization of β-ketothioamides with aryldiazonium salts catalyzed by Ru­(bpy)3Cl2 has been realized to provide 2,4-disubstituted 5-imino-1,2,3-thiadiazoles in good to high yields under mild reaction conditions for the first time. The reaction proceeded via an α-phenylhydrazone adduct of thioamides leading to 1,2,3-thiadiazoles via N–S bond formation at room temperature. Notably, the products possess Z-stereochemistry with regard to the exocyclic CN double bond at the 5-position of the ring.

We have developed an electrochemical approach for the synthesis of fully substituted 1,2,3-thiadiazoles from α-phenylhydrazones at room temperature, which is very challenging and complementary to the conventional thermal reactions. The key step involves anodic oxidation of phenylhydrazone derivatives at a constant current followed by N,S-heterocyclization. The protocol is remarkable in that it is free of a base and free of an external oxidant and can be converted to a gram scale for postsynthetic drug development with functional thiadiazoles. Most importantly, the electrochemical transformation reflected efficient electro-oxidation with an operationally friendly easy procedure with ample functional molecules. Cyclic voltammograms support the mechanism of this electro-oxidative cyclization process.

With unique chemical reactivity, α‐oxoketene S,S‐ and N,S‐acetals have attracted enormous attention in the past decades, whereas limited reports exist for their synthesis via eco‐compatible protocols. Herein, we developed a one‐pot protocol for symmetrical and unsymmetrical α‐oxoketene S,S‐/N,S‐acetals through chemoselective alkylation of α‐enolic dithioesters using Mitsunobu chemistry at room temperature. The operationally simple and user‐friendly mild protocol tolerates a wide range of alcohols and α‐enolic dithioesters/β‐ketothioamides. Short reaction time, good yields, highly selective C−S functionalization, and E/Z‐stereoselectivity are imperative characteristics of this strategy.