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Title: The α-alkylation of ketones using hydrogen borrowing catalysis
Author: Akhtar, Wasim
ISNI:       0000 0004 7966 065X
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2018
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Introduction - Hydrogen Borrowing Alkylation Reactions Using Alcohols The introduction reviews the origins of hydrogen borrowing catalysis and how it has been applied to utilise alcohols as alkylating agents. The predominant focus is on highlighting the scope for the use of primary alcohols in the α-alkylation of ketones. Other nucleophiles are discussed with respect to the use of secondary alcohols as alkylating agents. Examples of related methodologies are also briefly discussed. Results and Discussion - Formation of α-Branched Products Using Primary Alcohols This chapter explores the alkylation of several ketone substrates and identifies cyclopropyl ketones as key structural motifs that facilitate the formation of α-branched products using primary alcohols. The development of an iridium-catalysed protocol for this reaction is described, including the optimisation of reaction conditions and investigation of the substrate scope with respect to the ketone and alcohol. The derivatisation of the resulting α-branched cyclopropyl ketones is also explored through utilisation of several ring-opening reactions. Results and Discussion - Formation of β-Branched Products Using Secondary Alcohols This chapter focuses on the development of an Ir-catalysed procedure for the alkylation of methyl ketones using secondary alcohols to form β-branched products. In developing this procedure, ortho-disubstituted aryl ketones were identified as key structural motifs that facilitated the reaction due to the unique properties they possessed. An overview of the optimisation of reaction conditions is provided, followed by exploration of the substrate scope with respect to the methyl ketone and the secondary alcohol. Derivatisation of the resulting β-branched products through bromine-initiated release of the aryl group, followed by trapping with several nucleophiles led to the formation of carboxylic acid derivatives. The final part of the chapter introduces preliminary studies towards the development of an asymmetric route to β-branched products. Results and Discussion - Formation of Cyclic Products Using Diols This chapter explores the development of an unprecedented Ir-catalysed procedure for alkylation of a methyl ketone using diols to form five-, six- and seven-membered carbocyclic rings. The optimisation of the reactions conditions is described followed by a systematic investigation into the diastereoselectivity observed in the formation of the carbocyclic rings. With the formation of cyclohexane rings identified as being most effective under the reaction conditions, these were then explored further in a more general substrate scope. The derivatisation of the cyclic products was also explored through a bromine-mediated release of the aryl group followed by trapping with a variety of nucleophiles. Experimental Section Experimental procedures are provided along with full spectroscopic characterisation of the compounds synthesised.
Supervisor: Donohoe, Timothy Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Organic Chemistry ; Organic compounds--Synthesis