Samarium Diiodide Mediated Cascade Radical Cyclisations of Methylenecyclopropane Derivatives

Watson, Faye Charlotte (2001) Samarium Diiodide Mediated Cascade Radical Cyclisations of Methylenecyclopropane Derivatives. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

This thesis is concerned with the synthesis, and radical cyclisations of methylenecyclopropane derivatives. Special interest is given to developing samarium diiodide mediated cascade radical cyclisations to create polycyclic systems.

Chapter 2 describes the synthesis of cyclopentanone (160 and 171) and cyclohexanone cyclisation precursors (184 and 185), and the investigations into their cascade cyclisation to produce bicyclic diols 162 and 186. The cyclisations of these precursors were found to be stereoselective due to chelation control with the samarium(III) ion. Chapter 3 describes the samarium diiodide mediated cascade cyclisation of methylenecyclopropyl cyclohexanone adducts with a pendant alkene or alkyne. The cascade reactions were found to proceed with high yields and diastereoselectivity, which was dependent on the presence of co-solvent HMPA or MeOH. Chapter 4 reports the investigations into the synthesis of natural product dihydrotournefortiolide 154 via a key radical cyclisation step using samarium diiodide. Cyclisations precursors 270 and 271 were synthesised from ethyl acetoacetate and preliminary studies into the cyclisations of such adducts were investigated. Chapter 5 outlines the samarium diiodide mediated radical cyclisations of simple α,β-unsaturated ketones as model studies towards the natural product dihydrotournefortiolide 154.