Diamine ligand for Cobalt-Catalyzed Aerobic Diamination of 1,1-disubstituted Alkenes with Aniline

The direct synthesis of 1,2-vicinal diamines via alkene diamination remains a significant challenge, particularly when utilizing free amines as nitrogen sources due to their strong coordination ability and propensity for oxidation. Here, we have reported a ligand-accelerated cobalt-catalyzed aerobic diamination of 1,1-disubstituted alkenes with anilines. This transformation employs a widely available CoI2 precursor combined with a simple diamine ligand, offering a practical alternative to the previously required Cp*Co(III) pre-catalysts. For Cp*Co(III) catalysis, DFT calculations revealed that the first C-N bond formation proceeds via a unique spin center shift mechanism involving spin state crossover, followed by a radical substitution for the second C-N bond formation. In the CoI2/diamine catalytic system, computational results suggest that a Co(III) species acts as the active catalyst, where the first C-N bond is also formed via a "spin center shift" mechanism, while the second C-N bond formation undergoes a one-electron reductive elimination. This work provides an efficient method for accessing vicinal diamines and unveils the mechanism of C-N bond-forming in Co(III) catalysis.