RESUMO
We describe a Cu-catalyzed cross-electrophilic coupling reaction for synthesizing α-amino acid derivatives from α-diazoesters with O-benzoyl hydroxylamines with Cu(OAc)2 as the catalyst and polymethylhydrosilane (PMHS) as the hydride reagent. Excellent functional group compatibilities were demonstrated. With ethyl 2-diazo-3-oxobutanoate as the precursor, a Cu-acetoacetate complex has been characterized by ESI-MS analysis. Results from the radical trap experiments are consistent with the intermediacy of nitrogen-centered radicals. This strategy offers a simple and inexpensive synthesis of α-amino acid derivatives.
RESUMO
We report the Ru-catalyzed enantioselective annulation of 1,4,2-dioxazol-5-ones to furnish γ-lactams in up to 97% yield and 98% ee via intramolecular carbonylnitrene C-H insertion. By employing chiral diphenylethylene diamine (dpen) as ligands bearing electron-withdrawing arylsulfonyl substituents, the reactions occur with remarkable chemo- and enantioselectivities; the competing Curtius-type rearrangement was largely suppressed. Enantioselective nitrene insertion to allylic/propargylic C-H bonds was also achieved with remarkable tolerance to the CâC and C≡C bonds.