Nitrative Difunctionalization of Alkenes via Cobalt-Mediated Radical Ligand Transfer and Radical-Polar Crossover Photoredox Catalysis

Herein, we report the rational design of a modular dual photoredox and cobalt catalysis paradigm for the difunctionalization of unsaturated hydrocarbons, unlocking the synthesis of a valuable but challenging 1,2-halonitroalkane substrate class. The protocol relies on the use of the redox-active organic nitrating reagent N-nitrosuccinimide as a source of nitryl radicals for the cobalt-mediated radical ligand transfer (RLT) methodology to form a carbon-halogen bond. This synergistic cooperation between a photocatalyst and a high-valence cobalt metal center occurs under mild reaction conditions and is capable of delivering 1,2-chloronitro- and 1,2-bromonitroalkanes in a single chemical operation while exhibiting high functional-group tolerance and exclusive regioselectivity for a variety of olefins. Mechanistic studies based on both experimental and spectroscopic analysis provided valuable insights into the radical nature of this dual catalytic halo-nitration process including evidence for cobalt as a radical halogen transfer catalyst. Furthermore, employing a net-neutral radical/polar crossover (RPC) approach under cobalt-free reaction conditions allowed us to accommodate a variety of external protic nucleophiles, including thiols, alcohols, acids, and, notably, substituted amines. Highly functionalized olefin scaffolds also successfully underwent nitrative difunctionalization, demonstrating the viability of these protocols for the late-stage functionalization of bioactive molecules.