Mechanistic duality of indolyl 1,3-heteroatom transposition.

A novel mechanistic duality has been revealed from the indolyl 1,3-heteroatom transposition (IHT) of N-hydroxyindole derivatives. A series of in-depth mechanistic investigations suggests that two separate mechanisms are operating simultaneously. Moreover, the relative contribution of each mechanistic pathway, the energy barrier for each pathway, and the identity of the primary pathway were shown to be the functions of the electronic properties of the substrate system. Based on the mechanistic understanding obtained, a mechanism-driven strategy for the general and efficient introduction of a heteroatom at the 3-position of indole has been developed. The reaction developed exhibits a broad substrate scope to provide the products in various forms of the functionalised indole. Moreover, the method is applicable to the introduction of both oxygen- and nitrogen-based functional groups.