Oxidative amidation of nitroalkanes with amine nucleophiles using molecular oxygen and iodine

The formation of amides and peptides often necessitates powerful, yet mild reagent systems. The reagents used, however, are often expensive and highly elaborate. New atom economical and practical methods that achieve such goals are highly desirable. Ideally, the methods should start with substrates that are readily available in both chiral and non-chiral forms and utilize cheap reagents that are compatible with a wide variety of functionalities, sterics, and epimerizable stereocenters. Herein, we developed a direct oxidative method to form amide and peptide bonds between amines and primary nitroalkanes simply by using I2 and K2CO3 under O2. Contrary to expectations, a 1:1 halogen-bonded complex forms between the iodonium source and the amine, which reacts with nitronates to form α-iodo nitroalkanes as precursors to the amides. Evidence now suggests the concept of umpolung amide synthesis (UmAS), involving putative N-iodo amines and α-amino nitroalkanes, warrants a mechanistic revisio