Synthesis of Diverse Metalloid Scaffolds via Transition Metal Catalysis
Creators: name: Roberts, Dean
Publisher: name: Lancaster University
Year: 2024
Subjects: Platinum
Catalysis
Hydrometallation
Silicon
Tin
Cross-coupling
Heterocycles

description: The work within this thesis describes developments in platinum catalysed
 
 hydrometallation for the synthesis of a range of diverse metalloid
 scaffolds.
 
 
 Chapter 1 contains a discussion of the application of organometalloid
 scaffolds
 
 in modern organic chemistry, as well as the widespread application of
 platinum
 
 complexes in the synthesis of said scaffolds. Notable developments in the
 field
 
 are summarised and the generally accepted mechanisms through which these
 
 reactions proceed are discussed.
 
 
 Chapter 2 examines the limitations of previous platinum complexes in
 catalysing
 
 selective hydrosilylations and the reasons for these limitations, as well
 as
 
 discussing the approaches to, and applications of, allylic amines in
 organic
 
 chemistry. The development of a PtCl2Xantphos catalyst to selectively
 carry out
 
 the hydrosilylation of propargylic amines and their derivatives is
 detailed as well
 
 as an investigation of the substrate scope. The synthetic utility of the
 products is
 
 investigated resulting in the development of a remarkably mild
 aziridination
 
 procedure.
 
 
 Chapter 3 builds on the previous aziridination procedure, demonstrating
 the
 
 applicability of the same sequence to access a range of diverse oxetanes
 by a
 
 hydrosilylation/cyclisation sequence. Previous approaches to oxetanes are
 
 discussed, as well as the utility of the scaffold in modern organic and
 medicinal
 
 chemistry. Attempts to expand the methodology to the synthesis of other
 
 heterocycles is also discussed.
 
 
 Chapter 4 details the study of platinum complexes in the context of
 
 hydrostannylation chemistry. Previous approaches to the scaffold are
 discussed,
 
 as well as the surprising lack of platinum-based catalyst systems. The
 effect of
 
 ligand denticity on stereoselectivity is reported, with a ligand
 controlled
 
 stereodivergency reported. Using a PtCl2(XPhos)2 catalyst system, a range
 of
 
 diverse organotin scaffolds are synthesized, and the benefits and
 limitations of
 
 the system in comparison to previous catalysts is discussed. A telescoped
 hydrometallation/cross-coupling sequence is developed to minimize the need
 to
 
 handle relatively unstable and toxic stannylated intermediates.
 
 
 Chapter 5 explores the application of platinum complexes bearing both NHC
 and
 
 phosphine ligands as hydrosilylation catalysts. The synthesis of a broad
 range of
 
 imidazolium salts is presented, alongside the synthesis of several
 platinum
 
 complexes via an organosilver intermediate. The efficacy of the complexes
 
 towards hydrosilylation is evaluated, and their poor performance
 rationalized in
 
 the context of similar complexes employed in the literature.
 
 
 Chapter 6 provides overall conclusions from the work presented as well as
 a
 
 discussion of further avenues of study.
 
 
 Chapter 7 provides bibliographic data for the thesis. Relevant
 characterisation
 
 data for novel compounds or compounds prepared by novel routes can be
 
 found at the end of the relevant chapter.