Metal-Free Iodine-Catalyzed Oxidation of Ynamides and Diaryl Acetylenes into 1,2-Diketo Compounds

Metal-free oxidation of ynamides is described, employing pyridine-N-oxides as oxidants under molecular iodine catalysis. In stark contrast to Bronsted acid catalysis, iodophilic activation of ynamides diverts the reaction manifold into a dioxygenation pathway. This oxidation is very rapid at room temperature with only 2.5 mol % I-2. Furthermore, this protocol could be extended to nonactivated alkynes, such as diarylacetylenes, to deliver various benzil derivatives.