Nickel -Catalyzed Rearrangement of Aldoximes or Aldehyde into Primary Amides

Abstract

The synthesis of primary amides from aldehydes was developed using the commercially available catalyst [NiCl2(PPh3)2] without the use of any chelating agents, additives, or harsh reagents in a one-pot process. We investigated the effects of catalyst screening, reaction time, solvent, bases, and catalyst loading were studied for this reaction. The methodology demonstrated broad substrate compatibility, proceeding efficiently with a diverse range of aldehydes. These included electron-rich, electron-deficient, halogenated, ring-extended, and aliphatic aldehydes, as well as substrates featuring extended conjugation and hetero-aromatic frameworks. A nickel catalytic system was developed, and the amides were obtained in good to excellent yields through the reaction of aldehydes and hydroxylamine hydrochloride in toluene with NaHCO3. Finally, a plausible mechanism involving Ni(II)/(III) species is proposed and elucidated through DFT calculations at BP86/Def2-TZVP level.