In pursuit of functional analogues to the oxyferryl in cytochrome P450, we pursued coordination complexes of weak-field dipyrrin ligands. Oxidative group transfer to a ferrous dipyrrinato complex yielded a ferric iminyl radical competent for nitrene delivery to the C-H bonds in olefinic and aliphatic substrates. The unique electronic structure of the reactive intermediate facilitates nitrene delivery via attenuation of the strength of the metal ligand multiple bond, as well as preservation of a quintet spin manifold throughout the catalytic cycle. This strategy facilitates the direct amination of aliphatic C�H bonds to furnish cyclic amine products under mild conditions. Using organic azides as the oxidizing agent, allylic, benzylic, tertiary, secondary, and primary C�H bonds have been catalytically functionalized to furnish azetidine (4-membered), pyrrolidine (5-membered), and piperidine (6-membered) N�heterocyclic products. The oxidative amination of C�H bonds preferentially to more electron-rich substrates (olefins and aromatics) is made possible by the unique electronic structure of the putative iron-stabilized iminyl radical intermediate. Progress towards the development of a stereoselective version of this cyclization reaction will be discussed.

High-spin metal-ligand multiple bonds for catalyzing C-H bond functionalization

248th National Meeting (2014)

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