A computational study of the copper(II)-catalyzed enantioselective intramolecular aminooxygenation of alkenes.

The origin of the enantioselectivity in the [Cu(R,R)-Ph-box](OTf)2-catalyzed intramolecular aminooxygenation of N-sulfonyl-2-allylanilines and 4-pentenylsulfonamides to afford chiral indolines and pyrrolidines, respectively, was investigated using density functional theory (DFT) calculations. The pyrrolidine-forming transition-state model for the major enantiomer involves a chairlike seven-membered cyclization transition state with a distorted square-planar copper center, while the transition-state model for the minor enantiomer was found to have a boatlike cyclization geometry having a distorted tetrahedral geometry about the copper center. Similar copper-geometry trends were observed in the chiral indoline-forming reactions. These models were found to be qualitatively consistent with experimental results and allow for rationalization of how substitution on the substrate backbone and N-sulfonyl substituent affect the level of enantioselectivity in these and related copper(II)-catalyzed enantioselective reactions.