Mechanism of Oxidative Amidation of Nitroalkanes with Oxygen and Amine Nucleophiles by Using Electrophilic Iodine

Recently, we developed a direct way to oxidatively convert primary nitroalkanes into amides. This entailed mixing an iodonium source with an amine, a base, and oxygen. Herein, we systematically investigated the mechanism and likely intermediates. We conclude that an amine-iodonium complex first forms through N-halogen bonding. This complex reacts with aci-nitronates to give both alpha-iodo and alpha-,alpha-diiodo nitroalkanes. These iodinated species can act as alternative sources of electrophilic iodine and also generate an extra equimolar amount of “I+” under O2. In particular, evidence supports alpha-,alpha-diiodo nitroalkanes reacting with molecular oxygen to form a peroxy adduct; alternatively, these tetrahedral intermediates rearrange anaerobically into a cleavable nitrite ester. In either case, activated esters are proposed form, which eventually react with nucleophilic amines in a traditional fashion.