Elemental Sulfur/Base/Water: An Efficient System for the Synthesis of 2-Phosphoryl-Substituted Benzazoles via a Willgerodt-Kindler-Type Reaction

We report an elemental sulfur/base/water system enabling the synthesis of 2-phosphorylbenzazoles via a Willgerodt-Kindler-type reaction of <i>o</i>-hydroxy/amino/mercaptoanilines with substituted phosphorylmethanes. The developed protocol is efficient under metal- and catalyst-free conditions and is easily scalable. The scope and limitations of this transformation have been investigated; a rationalization of the mechanism is presented.