Chemoselective reactions of organoboron compounds

  • John James Molloy

Student thesis: Doctoral Thesis

Abstract

The Suzuki-Miyaura reaction is a landmark discovery which has revolutionised the field of palladium catalysis. Since its inception, reaction development has not only progressed the range of electrophiles which can be adopted in this transformation but has significantly enhanced the scope of organoboron reagents which can be used, cementing the reaction as the most favoured method for C-C bond formation. Despite these advances, investigation around this key transformation is continuous. A key highlight of this reaction, which is desirable to the synthetic community, is the chemoselectivity shown between, competing electrophiles, through selective oxidative addition based on electronics and bond dissociation energies, and competing nucleophiles, through selective transmetalation using boron protecting groups. The use of boron protecting groups typically adds several steps to a synthetic sequence and, as such, is an aspect which this investigation looks to address by establishing chemoselectivity between ostensibly equivalent organoboron species. In order to probe this chemoselectivity a workhorse reaction was chosen: The Brown oxidation. This work describes the development of a chemoselective oxidation of competing organoboron species with a thorough investigation into the origin of this observed chemoselectivity. This study serves as a platform for chemoselectivity in other organoboron reactions without the necessity of protecting groups. A key mechanistic event in the SM reaction which has recently been disclosed in several mechanistic investigations, is the anion metathesis step.Although this critical step has been suitably highlighted in these studies, we believe control of this event would provide a powerful, yet untapped, control vector in PdII catalysis. The following study highlights how an ion metathesis can be regulated to facilitate discrimination between competing Mizoroki-Heck and Suzuki-Miyaura pathways. To interrogate this vinyl BPin, a competent nucleophile in both cross-couplings, is employed as a bifunctional chemical probe. Ultimately, this thesis will discuss unexplored chemoselectivity of organoboron compounds and how this selectivity can be leveraged for the improvement of synthetic chemistry.
Date of Award1 Apr 2018
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council)
SupervisorWilliam Kerr (Supervisor) & (Supervisor)

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