Synthesis and Analysis of Substituted Fluxional Carbon Cages

Abstract

Fluxional carbon cages,[1] specifically those of the bullvalene and barbaralane homologues, are of fundamental interest within the organic and materials chemistry, due to their unique ‘shapeshifting’ properties, a term devised by Bode and co-workers.[2] These ‘shapeshifting’ properties, which occur due to strain-assisted Cope rearrangements within the molecular framework, allow for a dynamic series of species within their accessible population at ambient temperatures, particularly in the case of bullvalene.[3] In recent years, the efficient access to bullvalene derivatives has increased in diversity, owing to innovative synthetic methods.[4] As such, their use has been investigated in the context of more applications, namely as chemical sensors, polymers and antibiotics.[2b,5] Fluxional carbon cage derivatives with a specific structure-property relationship, particularly those with biological applicability, are infrequent in the literature. Thus, the study of shapeshifting compounds (especially in a biological context) is of fundamental interest.
This thesis examines the synthetic access to both bullvalene and barbaralane, from both a classical and modern perspective, whilst also detailing their applications to date. The 3D shape diversity of bullvalene is then explored, demonstrating how its inherent stereodynamics draw comparisons with commonly used ring systems in medicinal chemistry. Then, fluxional carbon cages are investigated in the biological milieu, exploring how these species behave in biomolecules, such as proteins. The functionalisation of the bullvalene scaffold with redox controllable moieties (i.e. viologens) is then examined, to further probe how bullvalene’s shapeshifting properties may have an effect on the physical properties of appended redox active substituents.
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