A Computational Study of the Copper(II) Catalyzed Enantioselective Intramolecular Aminooxygenation of Alkenes

摘要

The origin of 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 chair-like 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 boat-like 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 allowed for rationalization of how substitution of the substrate backbone and N sulfonyl substituent affected the level of enantioselectivity in these and related copper(II)-catalyzed enantioselective reactions.