Epoxidation of a Cyclic Allyl-Amine by a Bifunctional Peracid: Origins of the Stereocontrol
Origins of Contrasteric π-Facial Selectivity in Epoxidations of Encumbered Tetrahydropyridines by a Bifunctional Peracid: S. Chen, S. Wang, K. N. Houk
Synlett 2019, 30, 459–463
Stereoselective epoxidations of allylic alcohols are well documented and the origin of stereocontrol has been studied in great detail. Much less work has been devoted to nitrogen-directed stereoselective epoxidations of allylic amines, and computational studies aimed at elucidating the origin of stereocontrol in these systems had never been reported before the recent Synlett paper authored by Professors Shuming Chen and Kendall N. Houk from University of California, Los Angeles (USA). Density Functional Theory (DFT) calculations showed that a bifunctional peracid oxidant features a diastereofacial selectivity dictated by a hydrogen bond involving the carboxyl group and the nitrogen atom, which directs the facial approach of the peroxycarbonyl group to the alkene.