Copper‐Catalyzed Aerobic Oxidations of 3‐N‐Hydoxyaminoprop‐1‐ynes to Form 3‐Substituted 3‐Amino‐2‐en‐1‐ones: Oxidative Mannich Reactions with a Skeletal Rearrangement

Cu‐catalyzed aerobic oxidations of readily available 3‐N‐hydroxyaminopro‐1‐ynes with water, alcohols, or thiols to form diverse 3‐substituted 3‐amino‐2‐en‐1‐ones are described. The utility of this catalysis is manifested by a wide scope of applicable N‐hydroxyl propargylamines and nucleophiles, thus enabling the design of one‐pot cascade or two‐step sequential reactions. Besides synthetic significances, such oxidative Mannich reactions are mechanistically interesting because structurally reorganized products were obtained. Our mechanistic studies reveal that the aerobic oxidations involve initial formation of nitrone intermediates, followed by the attack of nucleophiles. Herein, water and MeOH implement the conversion of nitrone intermediates to reaction products in two distinct pathways.