Ligand-centered redox-driven Zn(ii)-catalyzed anti-Markovnikov hydroamination of activated alkenes with primary aromatic amines via aminium radical cations

Abstract

A ligand-centered redox-driven strategy for anti-Markovnikov hydroamination of electron-deficient alkenes, including acrylates, acrylonitrile, and acrylamides, enabled by a well-defined Zn(II) catalyst bearing a redox-active arylazo–phenanthroline ligand, is reported. The azo-functionalized ligand serves as the key redox mediator, enabling single-electron transfer (SET) from primary aromatic amines to the low-lying π*-acceptor orbital of the ligand scaffold, generating aminium radical cation intermediates that engage in regioselective radical hydroamination under thermal conditions (100 °C), circumventing the need for precious metals, external oxidants, or photochemical activation. The protocol demonstrates broad substrate scope and functional group tolerance, efficiently transforming a variety of amines, including heteroaryl, electron-rich, and complex amines derived from natural products, into valuable hydroaminated products. Mechanistic studies support a radical pathway initiated by SET to the azo-functionalized catalyst, with the redox-active ligand mediating all key electron-transfer events, while the Zn(II) center acts as a coordination scaffold. This work highlights the potential of redox-active ligand systems to enable sustainable radical pathways for C–N bond formation, introducing a new catalytic paradigm for the selective hydroamination of electron-deficient alkenes to access linear alkylamine frameworks.