Elemental Sulfur Mediated Sulfurization and Base mediated Cyclodesulfurization Strategy toward the Synthesis of 2-Aryl/Alkyl Azoles: Photophysical Studies

An efficient, metal free and solvent free strategy has been established for the synthesis of 2 aryl/alkyl azoles by employing a sulfur mediated sulfurization followed by a base driven cyclodesulfurization pathway. The transformation utilizes 2 aminophenol and 2 aminothiophenol in combination with aryl and alkyl nitriles, which are activated by sulfur to generate thioamide intermediates. These intermediates subsequently undergo desulfurization and intramolecular cyclization under basic conditions, affording 2 aryl and alkyl benzoxazole and benzothiazole derivatives in excellent yields (72-93%). Comprehensive mechanistic investigations, including control experiments under both protonic (n butylamine) and non protogenic (TMEDA) bases, isolation and characterization of key intermediates, as well as confirmatory detection of in situ generated ammonia and H2S gas, provided deep insights into the reaction pathways. In addition, photophysical properties of the synthesized compounds were explored through UV Vis absorption and fluorescence spectroscopy, highlighting their potential for advanced functional applications.