Enantioselective Cp^xRh^III‐Catalyzed Carboaminations of Acrylates

Abstract

Enantioselective carboaminations of olefins constitute an attractive strategy for a rapid increase in molecular complexity from readily available starting materials. Reported here is an intermolecular asymmetric carboamination of acrylates using rhodium(III)-catalyzed alkenyl CÀH activations of N-enoxysuccinimides to generate the nitrogen and carbon portion for the transfer. A rhodium complex equipped with a tailored bulky trisubstituted chiral Cp x ligand ensures carboamination chemoselectivity as well high levels of enantioinduction. The transformation operates under mild reaction conditions at ambient temperatures and provides access to a variety of a-amino esters in good yields and excellent enantiomeric ratios of > 99.5:0.5.

Chiral Cyclopentadienyl Ligands: Design, Syntheses, and Applications in Asymmetric Catalysis

“…[59] Theg enerally accepted mechanism for the reaction is shown in Scheme 18 a. After in situ generation of the active Cp X Rh III catalyst 76,t he hydroxamate functionality coordinates to the metal center (77). Subsequently,acarboxylateassisted concerted metalation-deprotonation (CMD) takes place, [69] lyst.…”

Chiral Cyclopentadienyl Ligands: Design, Syntheses, and Applications in Asymmetric Catalysis

“…Alternatively,t he authors demonstrated later that by changing the catalyst from Mannitol-CpRh15 to BINOL-CpRh16,a nd running the reaction in methanol instead of trifluoroethanol, carboamination acyclic products 110 were generated instead. [77] Ab road range of unnatural a-amino acids (EWG = CO 2 R) were synthesized accordingly in moderate to high yields and with excellent enantioselectivity. Presumably,t he MeOH solvent assists by nucleophilic ringopening of the N-enoxysuccinimide substrate,being incorporated into the methyl ester products 110.…”

“…[59] Theg enerally accepted mechanism for the reaction is shown in Scheme 18 a. After in situ generation of the active Cp X Rh III catalyst 76,t he hydroxamate functionality coordinates to the metal center (77). Subsequently,acarboxylateassisted concerted metalation-deprotonation (CMD) takes place, [69]…”