Sulfur is a readily available, stable and nontoxic reagent. Sulfur is less reactive than oxygen.
The use of elemental sulfur as traceless oxidizing agent enables a remarkably simple solvent-free and catalyst-free synthesis of benzazoles from alkylamines and o-hydroxy/amino/mercaptan anilines.
T. B. Nguyen, L. Ermolenko, W. A. Dean, A. Al-Mourabit, Org. Lett., 2012, 14, 5948-5951.