Catalyzed Cyclizations Leading to Enrichment of Functionality and Chirality. A General Approach to Dibenzocyclooctadiene Lignans from α,ω-Diynes

The [B−Sn]-mediated cyclization of α,ω-diynes results in not only an increase in the functionalizable groups (incorporated as highly versatile vinyl−B and vinyl−Sn groups) but also an increase in new serviceable stereochemical elements. The alkylidene functionalities at C7 and C8 offer unprecedented opportunities for the synthesis of highly functionalized dibenzocyclooctadienes. Examples of interiotherins and gomisins are provided.