Yingfu Lin1,2, William J Hirschi3, Anuj Kunadia2, Anirudra Paul1,2, Ion Ghiviriga4, Khalil A Abboud5, Rachael W Karugu3, Mathew J Vetticatt3, Jennifer S Hirschi3, Daniel Seidel1,2. 1. Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States. 2. Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States. 3. Department of Chemistry, Binghamton University, Binghamton, New York 13902, United States. 4. Center for NMR Spectroscopy, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States. 5. Center for X-ray Crystallography, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States.
Abstract
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.
β-Amino esters are obtained with high levels of enantioselectivity via the conjugate addition of n class="Chemical">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.
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