Extending the scope of chromium-manganese redox-coupled reactions: A one-pot synthesis of benzoxazoles

A critically important strategy for synthetic chemistry is the development of "domino" processes: those capable of concatenating multiple transformations into a single step. Such transformations not only provide an increase in synthetic efficiency, but also imply the development of a significant degree of mechanistic understanding. We report herein a new domino reaction, in which a chromium-manganese redox couple is employed both to catalytically reduce an o-hydroxy nitroarene and to oxidatively cyclize a subsequently formed imine. We find that the reaction is most effective for starting o-hydroxy nitroarenes with a strongly electron-withdrawing group at the para position.