The synthesis of lignans and related structures using quinodimethanes and isobenzofurans: approaches to the podophyllins

Abstract

Novel routes to 1-aryl-5,6-dialkoxy-1,3-dihydrobenzo[c]thiophene 2,2-dioxides (13) and to the corresponding benzo[c]furan (8) have been developed; these species yield quinodimethanes (12)via thermal extrusion of SO₂ and isobenzofurans (5c) in an acid-catalysed process, respectively, which then react with various dienophiles to provide structural analogues of the aryltetralin and arylnaphthalene lignans.