Asymmetric One-Pot Sequential Organo- and Gold Catalysis for the Enantioselective Synthesis of Dihydropyrrole Derivatives

A direct asymmetric one-pot synthesis of optically active 2,3-dihydropyrroles from propargylated malononitrile and N-Boc-protected (Boc = tert-butoxycarbonyl) imines is presented. The approach is based on a bifunctional organocatalytic Mannich-type reaction and a subsequent gold-catalyzed alkyne hydroamination and isomerization. The compatibility of both catalytic systems is presented and the overall transformation results in good yields (up to 70%) with high selectivities (endolexo > 10:1) and enantioselectivities (up to 88% ee). The absolute configuration of the final products is unambiguously established by X-ray analysis. To highlight the synthetic potential of the accessed heterocyclic compounds, their transformation into 1-pyrrolines, which represent direct precursors of pyrrolidines, is presented.