Substrate-Directed Enantioselective Aziridination of Alkenyl Alcohols Controlled by a Chiral Cation

Abstract

Alkene aziridination is a highly versatile transformation for the construction of chiral nitrogen-containing com-pounds. Inspired by the success of analogous substrate-directed epoxidations, we report an enantioselective aziridination of alkenyl alcohols which enables asymmetric nitrene transfer to alkenes with varied substitution patterns, including those not covered by the current protocols. We believe that our method is effective because it is substrate-directed, exploiting a net-work of attractive non-covalent interactions between the substrate, an achiral dianionic rhodium(II,II) tetracarboxylate di-mer and its two associated cinchona alkaloid-derived cations. It is these cations that provide a defined chiral pocket in which the aziridination can occur. In addition to a thorough evaluation of compatible alkene classes, we advance a practical mne-monic to predict reaction outcome and disclose a range of post-functionalization protocols which highlight the unique syn-thetic potential of the enantioenriched aziridine-alcohol products.