We report an elemental sulfur/base/water system enabling the synthesis of 2-phosphorylbenzazoles via a Willgerodt-Kindler-type reaction of o-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.
Chursin et al. (Thu,) studied this question.