An iron(ii)-based metalloradical system for intramolecular amination of C(sp²)–H and C(sp³)–H bonds: synthetic applications and mechanistic studies

A catalytic system for intramolecular C(sp2)-H and C(sp3)-H amination of substituted tetrazolopyridines has been successfully developed. The amination reactions are developed using an iron-porphyrin based catalytic system. It has been demonstrated that the same iron-porphyrin based catalytic system efficiently activates both the C(sp2)-H and C(sp3)-H bonds of the tetrazole as well as azide-featuring substrates with a high level of regioselectivity. The method exhibited an excellent functional group tolerance. The method affords three different classes of high-value N-heterocyclic scaffolds. A number of important late-stage C-H aminations have been performed to access important classes of molecules. Detailed studies (experimental and computational) showed that both the C(sp2)-H and C(sp3)-H amination reactions involve a metalloradical activation mechanism, which is different from the previously reported electro-cyclization mechanism. Collectively, this study reports the discovery of a new class of metalloradical activation modes using a base metal catalyst that should find wide application in the context of medicinal chemistry, drug discovery and industrial applications.