Wilmshurst, Martin Philip; (1998) Fluoroalkyl radical cyclisation reactions. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis is divided into four chapters. Chapter one contains three different introductory sections of relevance to the research carried out and opens with a short account of the applications of fluorinated organic molecules and materials. As the complexity of the molecules increases, some of the typical reagents and methods for fluorination are introduced. The effects which fluorination can have are explained by reference to the modes of action of appropriate biologically active molecules. The second part of the introduction contains material relating to the concept of "philicity" of radicals which is required for a full understanding of chapter two. Finally, a literature survey of 5-exo-trig cyclisation reactions of -heteroatom substituted radicals is presented together with the objectives of our own research. Chapter two consists of research in the area of fluoroalkyl radical cyclisation chemistry. An account of the novel use of dibromofluoromethane as an alkylating agent to prepare fluoroalkyl radical precursors is followed by a description of their 5-exo-trig- cyclisation reactions. Results from the use of tri(n-butyl)tin hydride / AIBN conditions are discussed with regard to the efficiency of cyclisation and the stereochemistry of the resultant cyclopentanoids produced as a function of the character of the radical. Samarium diiodide and cobalt mediated cyclisations are also demonstrated. The synthesis of a chiral building block intended as an intermediate to allow our methodology to provide nucleoside analogues appears towards the end of chapter two, as does an account of preliminary attempts to perform atom transfer cyclisation reactions involving difluoroalkyl radicals. Chapter three provides a formal description of the experimental results and the procedures used to obtain them.

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