Intramolecular Radical Oxygen-Transfer Reactions Using Nitroarenes

Intramolecular atom and group transfers are common steps in radical cascade reactions that have been utilized in various transformations. These types of radical translocations (group shifts) are reported for, but not limited to, alkenyl, alkynyl, aryl, cyano, chalcogenyl, and boryl groups. However, the intramolecular radical transfer of an oxygen atom is barely known. Herein, we disclose a radical transformation that allows intramolecular oxygen atom transfer to alkenes, utilizing the nitro functionality in nitroarenes as an oxygen donor. Reactions proceed via iron-catalyzed metal hydrogen atom transfer to alkenes with subsequent oxygenation resulting in alkene hydration. As compared to the intermolecular radical oxygenation, which is well investigated, the intramolecular variant offers advantages, particularly considering diastereoselective radical hydration of conformationally flexible alkenes. The aryl moiety connecting the reactive NO2-functionality to the alkene substrate can be cleaved after oxygen transfer, yielding products that derive from a formal diastereoselective intermolecular alkene hydration. On the other hand, the aniline entity resulting after oxygen transfer can be used for construction of nitrogen-containing heterocycles.

Automated summary

In this study, a radical transformation that enables intramolecular oxygen atom transfer to alkenes using the nitro functionality in nitroarenes as an oxygen donor is disclosed. The reaction proceeds via iron-catalyzed metal hydrogen atom transfer to alkenes and subsequent oxygenation, resulting in alkene hydration. Compared to intermolecular radical oxygenation, the intramolecular variant offers advantages, particularly in terms of diastereoselective radical hydration of conformationally flexible alkenes. The aryl moiety connecting the reactive NO2-functionality to the alkene substrate can be cleaved after oxygen transfer, yielding products derived from a formal diastereoselective intermolecular alkene hydration. Additionally, the resulting aniline entity after oxygen transfer can be used for the construction of nitrogen-containing heterocycles.