Structural Evidence for Aromatic Heterocycle N-O Bond Activation via Oxidative Addition

Abstract

Many methods report the scission of N-O bonds of aromatic heterocycles and their subsequent functionalization. Oxidative addition is one of the presumed pathways through which aromatic N-O bond activation with transition metals is achieved. We report the first well-defined pathway of (benz)isoxazole’s aromatic N-O bond activation through oxidative addition. We also provide control experiments, which show that aromatic N-O bonds may be broken by strong inorganic reductants. These results highlight that N-O bonds are susceptible to both reduction and oxidative addition, which has important implications for catalysis. Exploring the reactivity of one of these complexes toward a series of electrophiles leads to the discovery of a Staudinger-type β-lactam synthesis upon the reaction with a ketene. Finally, we demonstrate that the choice of different metal/ligand combinations allows for selective oxidative addition into either C-I bonds or N-O bonds in the presence of the other.