Elemental Sulfur Disproportionation in the Redox Condensation Reaction between o ‐Halonitrobenzenes and Benzylamines

The disproportionation of elemental sulfur at moderate temperatures is investigated in the redox condensation involving o ‐halonitrobenzenes 1 and benzylamines 2 . As a redox moderator, elemental sulfur plays the dual role of both electron donor and acceptor, generating its lowest and highest oxidation states: S −2 (sulfide equivalent) in benzothiazole 3 and S +6 (sulfate equivalent) in sulfamate 4 , and filling the electron gap of the global redox condensation process. Along with this process, a cascade of reactions of reduction of the nitro group of 1 , oxidation of the aminomethyl group of 2 , metal‐free aromatic halogen substitution, and condensation finally led to 2‐arylbenzothiazoles 3 .