Studies towards the taxane ring system via a cascade macrocyclisation–transannulation strategy

Abstract

Treatment of the ω-iodoacetylene 6 with Bu₃SnH–AIBN produces the taxane ring system 9 (45–60%) by way of transannular cyclisation from the macrocyclic vinyl radical intermediate 8, whereas the analogous iodoacetylenes 5a, 11 and 13a, together with the iodopolyenones 12a, 14a and 17, failed to give corresponding taxane systems, i.e. 7, 16 and 19 on similar treatment; instead only products resulting from direct reduction of the carbon–iodine bonds in these substrates were obtained.