Ruthenium-Catalyzed Asymmetric N-Acyl Nitrene Transfer Reaction: Imidation of Sulfide

The asymmetric nitrene transfer reaction is a useful and strong tool for the construction of nitrogen functional groups such as N-sulfonyl amide and carbamic ester in a highly enantioselective manner. On the other hand, there is a substantial limitation in this filed: the transfer of N-acyl amide via the corresponding nitrene intermediates is still difficult because N-acyl nitrenes undergo undesired nitrene dimerization or Curtius rearrangement. Herein, we achieved highly enantioselective imidation of sulfides via catalytic N-acyl nitrene transfer with (OC)ruthenium-salen complex 2b as the catalyst and 3-substituted 1,4,2-dioxazol-5-ones 1 as the nitrene source. Complex 2b can decompose dioxazolones 1 to the desired N-acyl nitrene intermediates without any activation via heating or UV irradiation, or transfer generating nitrene intermediates to the sulfur atom of sulfides with good to excellent enantioselectivities (<= 98% ee) without diazene and isocyanate contamination.