Asymmetric one-pot sequential organo- and gold catalysis for the enantioselective synthesis of dihydropyrrole derivatives

Chemistry. 2010 Aug 16;16(31):9478-84. doi: 10.1002/chem.201001123.

Abstract

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.