A cascade radical-mediated macrocyclisation–transannulation approach to oestrogen steroids

Abstract

A new approach to ring A aromatic steroids, based on cascade 13-endo-trig/dig macrocyclisations followed by sequential 5-exo-trig and 6-exo-trig transannulations, exemplified in the syntheses of the cis,anti,trans tetracycle 9 and the trans,syn tetracycle 13 from the ortho-substituted aryl polyen(yne) precursors, 8 and 12 respectively, is described.