Chiral counteranion controlled chemoselectivity in gold catalysed hydroamination/enantioselective formal 1,3-allylic alcohol isomerisation of β-amino-1,4-enynols

Abstract

A synthetic method for the preparation of 1,8-dihydroindeno[2,1-b]pyrroles and pyrrol-2-yl methanols in an enantioselective manner that relies on the chiral gold(I)-catalysed reactions of β-amino-1,4-enynols is described. A divergence in product selectivity was achieved by exploiting the electrostatic interactions between the chiral counteranion of the metal catalyst and the substrate. With a gold(I) complex containing a chiral N-triflyl phosphoramide-based counteranion, tandem dehydrative Nazarov-type electrocyclisation/hydroamination of the substrate was found to selectively occur to afford the indeno-fused pyrrole adduct. In contrast, changing to a chiral phosphate-based counteranion was observed to result in a hydroamination/enantioselective formal 1,3-allylic alcohol isomerisation cascade pathway to give the 1H-pyrrole derivative.

Keywords

• Asymmetric catalysis
• Gold
• Cycloisomerisation
• N-Heterocyclic synthesis
• Synthetic methods