Merging Photoexcited Nitroarenes with Lewis Acid Catalysis for the Anti-Markovnikov Oxidation of Alkenes

A protocol for the oxidation of alkenes to carbonyls and acetonides via the interplay of photoexcited nitroarenes and Lewis acid catalysis is described. Terminal 1,1-disubstitued alkenes were oxidized selectively to the aldehyde products, while tri- and tetrasubstituted alkenes generated ketone products with anti-Markovnikov selectivity. Terminal mono-substituted alkenes were oxidized to acetonides when acetone was employed as a co-solvent. The mild conditions of the reaction allow for a wide range of alkenes to be oxidized. Mechanistic studies support that Lewis acid coordination to the 1,3,2-dioxazolidine intermediate formed by irradiation of the nitroarene and alkene results in a Meinwald-like rearrangement to generate carbonyl derivatives. In the presence of acetone, acetonides are formed from the same intermediate through a nucleophilic substitution pathway.