Hydrative Aminoxylation of Ynamides: One Reaction, Two Mechanisms

Organic synthesis boasts a wide array of reactions involving either radical species or ionic intermediates. The combination of radical and polar species, however, has not been explored to a comparable extent. Herein we present the hydrative aminoxylation of ynamides, a reaction which can proceed by either a polar-radical crossover mechanism or through a rare cationic activation. Common to both processes is the versatility of the persistent radical TEMPO and its oxidised oxoammonium derivative TEMPO⁺ . The unique mechanisms of these processes are elucidated experimentally and by in-depth DFT-calculations.