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 (endo/exo > 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.
Monge
David
D
Center for Catalysis, Department of Chemistry, Aarhus University, 8000 Aarhus C, Denmark.
Jensen
Kim L
KL
Franke
Patrick T
PT
Lykke
Lennart
L
Jørgensen
Karl Anker
KA