Copper-Catalyzed Asymmetric Propargylation of Cyclic Aldimines

The copper-catalyzed asymmetric propargylation of cyclic aldimines is reported. The influence of the imine trimer to inhibit the reaction was identified, and equilibrium constants between the monomer and trimer were determined for general classes of imines. Asymmetric propargylation of a diverse series of N-alkyl and N-aryl aldimines was achieved with good to high asymmetric induction. The utility was demonstrated by a titanium catalyzed hydroamination and reduction to generate the chiral indolizidines (-)-crispine A and (-)-harmicine.