Asymmetric Vinylogous Aza-Darzens Approach to Vinyl Aziridines

A new asymmetric approach to assemble <i>cis</i>-vinyl aziridines is reported. A reaction of strategically substituted dienolates, decorated with a γ-leaving group, with chiral sulfinimines afforded chiral vinyl aziridine products in good to excellent yields. This is the first systematic study toward the realization of a useful asymmetric vinylogous aza-Darzens reaction. The reaction is initiated by a <i>syn</i>-selective addition, affording <i>cis</i>-vinyl aziridine products after displacement of bromide. The low <i>syn</i>-diastereoselectivity is attributed to competing retro-Mannich pathways

New Class of Anion-Accelerated Amino-Cope Rearrangements as Gateway to Diverse Chiral Structures

We report useful new lithium-assisted asymmetric anion-accelerated amino-Cope rearrangement cascades. A strategic nitrogen atom chiral auxiliary serves three critical roles, by (1) enabling in situ assembly of the chiral 3-amino-1,5-diene precursor, (2) facilitating the rearrangement via a lithium enolate chelate, and (3) imparting its influence on consecutive inter- or intramolecular C–C or C–X bond-forming events via resulting chiral enamide intermediates or imine products. The mechanism of the amino-Cope rearrangement was explored with density functional theory. A stepwise dissociation–recombination mechanism was found to be favored. The stereochemistry of the chiral auxiliary determines the stereochemistry of the Cope product by influencing the orientation of the lithium dienolate and sulfinylimine fragments in the recombination step. These robust asymmetric anion-accelerated amino-Cope enabled cascades open the door for rapid and predictable assembly of complex chiral acyclic and cyclic nitrogen-containing motifs in one pot