Chemo‐ and Enantioselective Intramolecular Silver‐Catalyzed Aziridinations

Abstract

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.

Intermolecular [3+3] ring expansion of aziridines to dehydropiperi-dines through the intermediacy of aziridinium ylides

“…In the first case, INT2 forms azadiene INT3 through a cheletropic extrusion (via TS2), followed by a concerted aza-Diels-Alder cycloaddition (via TS3) to furnish 4ba. However, subjecting enantioenriched (S,R)-2a 67 to the standard reaction conditions resulted in transfer of the chirality to (R,R,R)-4aa with good fidelity (Fig. 3b).…”

“…The synthetic utility of the sequential nitrene/ carbene transfer reaction could be amplified by running it in tandem with asymmetric alkene aziridination to form enantioenriched piperidines over two steps. In 2017, we disclosed an asymmetric aziridination protocol using silver bisoxazoline complexes to enact intramolecular aziridination of homoallylic carbamate esters to achieve high enantioselectivities with a costeffective catalyst 67 . Application of our asymmetric aziridination to the carbamate of (3Z)-3-penten-5-phenyl-1-ol gave enantioenriched (S,R)-2a 67 in 95:5 er (Figs.…”

Synthesis of Fluorine‐Containing Molecular Entities Through Fluoride Ring Opening of Oxiranes and Aziridines

“…In 2017, Schomaker and co‐workers disclosed the stereo‐ and regio‐selective transformation of compound 295 into fluorinated amine 296 with Et 3 N/3HF. The starting material was prepared by silver‐catalyzed chemo‐ and enantioselective intramolecular aziridination . Then, Alanine et al reported the regioselective ring opening of aziridine 297 in 2018.…”

Enantioselective Synthesis of Aminodiols by Sequential Rhodium‐Catalysed Oxyamination/Kinetic Resolution: Expanding the Substrate Scope of Amidine‐Based Catalysis

“…However, to the best of our knowledge, the asymmetric synthesis of vicinal amino alcohols through an enantioselective catalytic oxyamination of dienyl carbamates or through kinetic resolution (KR) of the intermediate racemic oxazolidinones is still unexplored (Scheme c) . Herein, we report a tandem regio‐ and stereocontrolled rhodium‐catalysed intramolecular aziridination/ring opening of 2,4‐dien‐1‐yl carbamates with oxygen nucleophiles, followed by an organocatalysed KR of the resulting oxazolidinones, to obtain enantioenriched 4‐ene‐2‐amino‐1,3‐diol derivatives (Scheme ).…”