This thesis describes the use of organoborate rearrangement reactions to generate quaternary carbon centres, with the ultimate goal of exploring new procedures for the asymmetric synthesis of chiral quaternary carbon centres. Chapter One: this chapter contains a historical review of the use of organoboranes in organic synthesis, focusing mainly on the use of boronic esters in asymmetric organic synthesis. Chapter Two: this chapter focuses on attempts at developing a catalytic method for the generation of quaternary stereocentres using migration reactions of boronic esters with n-butyllithium in the presence of chiral catalysts. This study showed that the reaction is stoichiometric in the absence of the Lewis acid. However, there were strong indications of catalytic turn over in some experiments. Chapters Three and Four: these chapters focus on attempts at designing a chiral version of the DCME reaction using sulfur compounds. Chapter Three focuses on attempts at evaluating a heterocyclic system, specifically a dithiane, as a stereocontrol agent in its reaction with trialkylboranes. The study showed that using 2-methoxy-1,3-dithiane-oxide achieved formation of the double and triple migration product but in poor yield. Chapter Four contains a detailed investigation into the synthesis and evaluation of non-cyclic sulfur compounds such as sulfoxides, sulfoximines, sulfilimines and sulfones for generation of chiral tertiary alcohols. The study of the reaction of dichloromethyl phenyl sulfoxide with trialkylboranes showed a new type of aldol-like reaction. This reaction was utilised to synthesise a series of new compounds. Also, the study of the reaction of dichloromethyl-p-tolyl sulfone with trialkylboranes showed a new type of reaction by replacing the hydrogen with the alkyl group from the trialkylborane. Finally, the study of the reaction of N-methyl-S-(dichloromethyl)-S-phenylsulfoximine with trialkylboranes showed production of the desired triple migration product in moderate to very good yield.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:665874 |
| Date | January 2015 |
| Creators | Alabdullah, Basil |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/75961/ |
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