A Selenourea-Thiourea Brønsted Acid Catalyst Facilitates Asymmetric Conjugate Additions of Amines to α,β-Unsaturated Esters.
Yingfu LinWilliam J HirschiAnuj KunadiaAnirudra PaulIon GhivirigaKhalil A AbboudRachael W KaruguMathew J VetticattJennifer S HirschiDaniel SeidelPublished in: Journal of the American Chemical Society (2020)
β-Amino esters are obtained with high levels of enantioselectivity via the conjugate addition of cyclic amines to unactivated α,β-unsaturated esters. A related strategy enables the kinetic resolution of racemic cyclic 2-arylamines, using benzyl acrylate as the resolving agent. Reactions are facilitated by an unprecedented selenourea-thiourea organocatalyst. As elucidated by DFT calculations and 13C kinetic isotope effect studies, the rate-limiting and enantiodetermining step of the reaction is the protonation of a zwitterionic intermediate by the catalyst. This represents a rare case in which a thiourea compound functions as an asymmetric Brønsted acid catalyst.
Keyphrases
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