Fe/S-Catalyzed Redox Condensation of <i>o</i>-Nitrophenols with Isothiocyanates to 2-Aminobenzoxazoles

Abstract

As frequently encountered byproducts of isocyanate chemistry, hydrogen sulfide and related sulfur containing compounds should be treated in a safe way to lower their adverse health and environmental effects, especially in large scale syntheses. As a proof of concept, we report herein an example of in situ recycling of sulfur byproduct to reductant in the synthesis of bioactive 2-aminobenzoxazoles <b>3</b>. Using an Fe/S catalytic system, this heterocyclic scaffold could be obtained from <i>o-</i>nitrophenols <b>1</b> with isothiocyates <b>2</b> via direct redox condensation consisting of reduction of the nitro group of <b>1</b> by the sulfur moiety of <b>2</b>.