Asymmetric nitrene transfer reactions are a powerful tool for the preparation of enantioenriched amine building blocks. Herein, we report chemo- and enantioselective silver-catalyzed aminations that transform di- and trisubstituted homoallylic carbamates into [4.1.0]-carbamate-tethered aziridines in good yields and ee up to 92%. The effects of the substrate, silver counteranion, ligand, solvent and temperature on both chemoselectivity and ee were explored to complement the scope of traditional metal-catalyzed nitrene transfer reactions. Stereochemical models were proposed to rationalize the observed absolute stereochemistry of the aziridines, which undergo nucleophilic ring-opening to yield enantioenriched amines with no erosion in stereochemical integrity.
reaction mixture was diluted with E2O and washed with H2O. The aqueous layer was extracted with E2O three times. The combined organic layer was washed with H2O (three times) and brine, dried over Na2SO4, filtered, and concentrated under reduced pressure. The crude material was purified by silica gel column chromatography (0→70% EtOAc/hexanes) to afford the desired trifluoromethylated alkyne S5 as a white solid (0.26 g, 44% yield); 1 H NMR (500 MHz, CDCl3) δ
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