Intramolecular (4+3) cycloaddition of pyrroles with epoxy enolsilanes.

Abstract

While (4+3) cycloadditions commonly proceed with furans and cyclopentadienes, the corresponding reaction with pyrroles is less common, since pyrroles tend to undergo Friedel-Crafts type of reactions, resulting in the restoration of aromaticity instead of cycloadditions. We have been developing the inter- and intramolecular (4+3) cycloadditions of furans and and other dienes using epoxy and aziridinyl enolsilanes as the electrophilic precursor.1 We found that pyrroles engage readily in intramolecular (4+3) cycloadditions with epoxy enolsilanes, resulting in polycyclic structures harboring a tropane nucleus. As a result, we are applying this reaction as the key strategy for the synthesis of the core of the galbulimima alkaloid, himandrine. Our progress in the synthesis will be reported.