Flexible metathesis-based approaches to highly functionalised furans and pyrroles

A range of differentially functionalised furans and pyrroles have been synthesised in short order by the judicious use of a ring-closing metathesis/aromatisation strategy. Two contrasting approaches are described exploiting a palladium-catalysed union of allylic alcohols and sulfonamides in one case, and a titanium mediated methylenation of homoallylic esters in another. A number of groups that are difficult to install via traditional methods were incorporated successfully. (c) 2007 Elsevier Ltd. All rights reserved.