Bismuth(iii) triflate-catalysed tandem cyclisations towards complex polycyclic ethers

Abstract

Herein is described a double cyclisation of α-hydroxy enol ethers with a tethered olefinic double bond, readily obtained from simple ketone precursors. Interesting bridged polycyclic compounds with an additional oxaspirocycle are formed under mild conditions using a low loading of recyclable bismuth(III) triflate as the catalyst. Some experimental evidence accounts for concerted (or pseudo-concerted) polycyclisation.