Formal Single-Carbon Atom Insertion into Imines as a Versatile Entry to Ketenimines and Diverse Amidine Derivatives

The insertion of single-carbon atoms into imines to generate versatile ketenimine intermediates has been achieved for the first time. These intermediates exhibit a broad reaction scope with various nucleophiles, making them suitable for the flexible synthesis of acyclic and cyclic amidines. We employed nitromethane as a single-carbon reagent to react with N-sulfonyl imines and oxidatively cyclize to α-nitroaziridines. Mechanistic experiments and in-depth computational studies strongly support α-nitroaziridines undergoing ring-opening rearrangement in the presence of mild base to form cumulative ketenimine intermediates.