Palladium-catalysed routes to the tricyclic core of the Stemona alkaloids

Heterocyclic product families include a wide and diverse range of natural and synthetic molecules, which exhibit a variety of biological activities. In particular this study will focus on the construction of the Stemona alkaloids, isolated from the roots and rhizomes of the Stemonaceae plant family. They possess the structurally novel and unique azepinoindole skeleton "B,C,D ring system." [Illustration omitted.] Studies towards the development of a novel methodology has been achieved. During our investigation we have developed a palladium(0)-catalysed [3+2]-cycloaddition strategy towards the rapid synthesis of heterocyclic skeletons, assembling polycyclic pyrrolidines and furan heterocycles from fused doubly activated vinylcyclopropanes. [Illustration omitted.] We have briefly investigated our palladium(0)-catalysed [3+2]-cycloaddition methodology towards doubly activated vinylcyclopropanes, preparing a selection of tetrahydrofuran and pyrrolidine precursors which underwent a Heck-mediated cyclisation. As well as further developing this methodology towards a tandem cycloaddition/Heck one-pot strategy. We hoped this initial ground work could be applied towards the construction of the tricyclic core of Stemona alkaloids. [Illustration omitted.]