Construction of trans-ring-fused compounds by radical cyclızation

Abstract

Enolates derived from bicyclic lactones of type (4) are alkylated with prop-2-ynylic (and allylic) bromides to give products (5) in which the unsaturated alkyl group is syn to the remaining ring-fusion hydrogen; prop-2-ynylic aldehydes can be used instead of halides and, in both cases, lactone opening with sodium phenyl selenide, esterification, and treatment with a stannane then leads to trans-ring-fused bicyclic compounds.