Murphy, John J. (2012) Studies in Synthesis and Organocatalysis: (i) The Design and Synthesis of Novel Electron Deficient Dienes and their Application in the First Enamine Activated Organocatalytic 1,6-Conjugate Addition. (ii) The Development of a New Organocatalytic Methodology through the Combination of DNA-Based Catalysis and Organocatalysis. PhD thesis, National University of Ireland Maynooth.
Preview
Thesis.pdf
Download (10MB) | Preview
Abstract
A novel approach to substrate design led to the development of charge de-localized extended
Michael acceptors. Using this methodology a family of both alkyl and aryl bis-phenylsulfonyl
butadienes were synthesised and characterised. The first enamine activated organocatalytic 1,6-
conjugate addition was performed on the sulfonyl acceptors, using aldehydic enamines, giving
excellent yields and selectivities (up to 98% yield, uniformly 99% ee). The mechanism of this reaction
was explored in detail. The products of these additions were fully characterised and were
subsequently used as substrates for the conjugate addition of methyllithium (52% yield, 12 : 1 d.r.)
and an organocatalysed inverse electron demand Diels-Alder reaction (DAINV) (76% yield, 3.1 : 1 : 1.5
d.r.). Combining the 1,6-addition and DAINV methodology let to the development of an
enamine/iminium ion organocatalytic cascade reaction which delivered a product with 5 contiguous
stereocenters (75% yield, 3.1 : 1 : 1.5 d.r.). We attempted to apply our 1,6-conjuagate addition
methodology to the synthesis of Sildenafil analogues. Several steps of this challenging synthesis
were completed. The step involving the oxidation of a homo-allylic alcohol remains to be solved.
Interestingly a DMSO-based oxidation generated a sulfur ylide in high yield (90%), a possible
explanation is provided.
A second class of butadienes, bis-cyano butadienes, that are suitable substrates for 1,6-conjugate
additions, were prepared and characterised. Addition of aldehydic enamines to these acceptors also
yielded a regioselective 1,6-adduct in high yield and selectivity (up to 75% yield, up to 99% ee). An
experimental investigation was performed into the synthesis of suitable trienes for 1,8-conugate
additions. A 1,3-bis-phenylsulfonyl hexatriene was synthesised and characterised which did not
undergo a selective 1,8-conjugate addition with aldehydic enamines. Upon heating, this triene was
found to undergo an electrocyclisation reaction to give a biphenyl with a near zero twist angle.
Synthesis of α,γ,ε-tris activated triene led to the isolation of a bis-phenylsulfonyl-cyano-arene and
not the desired triene.
A final experimental study was undertaken exploring the use of DNA and a suitable intercalating
organocatalyst in asymmetric transformations. The design, synthesis and characterization of a novel
achiral DNA-intercalating imidazolidinone was realized in high yield (40% yield over 4 steps). Several
synthetic routes to the intercalating imidazolidinone were explored. The catalyst was found to still
retain the ability to generate a reactive iminium ion and participate in a Diels-Alder reaction without
DNA, albeit in reduced potency (24% yield). Future work will entail the application of the
intercalating catalyst with salmon testes DNA.
Item Type: | Thesis (PhD) |
---|---|
Keywords: | Synthesis; Organocatalysis; Novel Electron Deficient Dienes; First Enamine Activated Organocatalytic 1,6-Conjugate Addition; Organocatalytic Methodology; DNA-Based Catalysis; |
Academic Unit: | Faculty of Science and Engineering > Chemistry |
Item ID: | 4771 |
Depositing User: | IR eTheses |
Date Deposited: | 18 Feb 2014 11:06 |
URI: | https://mu.eprints-hosting.org/id/eprint/4771 |
Use Licence: | This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here |
Repository Staff Only (login required)
Downloads
Downloads per month over past year