Studies on organic electron donors and their applications in chemistry

  • Florimond Cumine

Student thesis: Doctoral Thesis

Abstract

Electron transfer reactions using organic donors have been and are still successfully applied in the Murphy group to perform reductions usually requiring heavy metals. This thesis focuses on several organic electron donors used to: (i) promote the cross-coupling reaction between aryl halides and benzene, which was also studied with computational experiments, (ii) cleave carbon-oxygen bonds and (iii) reduce nitrobenzenes and azobenzenes.In addition, computational analysis of controversial literature proposals for a radical/electron transfer mechanism for ring-forming reactions of alkoxide allenes and amide allenes is reported and supports an anionic rather than a radical process.Chapter Two highlights the ability of diketopiperazines 1-4 to promote the cross-coupling reactions of aryl halides 5-16 with benzene in the presence of potassium tert-butoxide 17 to form biaryls 18-24 via electron transfer [graphic of electron transfer process].It also investigates the different outcomes of the reaction when a diketopiperazine is used or not, providing evidence for formation of a benzyne intermediate which can lead to both the coupling product with benzene (when aryl iodides are used) and to tert-butoxybenzenes.Chapter Three explores electron transfer reactions that lead to alkyl aryl ether deprotection. It highlights that tert-butyllithium 25 performs this deprotection and shows the series of reactions that led to evidence of an anionic addition of phenyllithium 26 to benzene and also of tert-butyllithium 25 to benzene [graphic of base-induced process and additions to Benzene with oxidative termination].Chapter Four focuses on a 4-DMAP-derived organic electron donor 32, commonly referred to as 'DMAP donor', that reduces nitrobenzene 34 and azobenzene 36, amongst others, under UV activation or thermal conditions, via successive single electron transfers. This chapter also discusses the unlikely possibility of an electron transfer from the DMAP donor 32 to the 1,2-diphenylhydrazine dianion 38 leading to the formation of aniline dianion 39. More rational mechanistic considerations involving the reduced diphenylhydrazine and dication 33 will be described to explain the formation of aniline 35 [graphic of DMAP electron donor].Chapter Five is a computational study of the 5-endo-trig cyclisation of alkoxideallenes and amide-allenes, discussing the process involved (electron transfer or direct intramolecular anionic cyclisation) and comparing it with the, non-experimentally observed, 4-exo-dig cyclisation [DMSO graphic].Chapter Six provides the detailed experimental procedures and data for the compounds that were synthesised and reported in this thesis.
Date of Award1 Apr 2017
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorJohn Murphy (Supervisor) & (Supervisor)

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