Electrochemical Synthesis of 1,2,3-Thiadiazoles from α‑Phenylhydrazones

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.