An exploration of the scope for radical-mediated transannular Diels-Alder reactions in polycycle synthesis

Abstract

Treatment of the iododienynone 4 with Bu 3SnH-AIBN results in the formation of the tricyclic enone 6 by way of radical-mediated macrocyclisation, to 5, followed by transannular Diels-Alder reaction. By contrast, similar treatment of 8 produced the tetracycle 12 (70%) rather than the Diels-Alder product 9, and the analogous system 13 gave rise to the novel tetracyclic diene-dione 18 presumably by way of the intermediates 14, 16 and 17.