Novel calcium complexes applied to intramolecular hydroamination catalysis

This thesis discusses the synthesis, characterisation, and reactivity studies of a range of new chiral calcium complexes supported by various polydentate N-donor ligands and their suitability as catalysts for intramolecular hydroamination. Chapter One outlines the case for developing organocalcium complexes, including a general overview of their current application to a variety of heterofunctionalisation reactions. Chapter Two introduces the chiral ethylene diamines which are extensively used as calcium supporting ligands and later as precursors for the synthesis of bisimidazoline and potential imoxazoline ligands. Chapter Two provides details of the diamine synthesis and includes studies related to racemisation concerns of the chiral centre. Chapter Three discusses novel calcium complexes supported by the chiral ethylene diamine analogues presented in Chapter Two. Complex synthesis, characterisation, and catalytic performance in intramolecular hydroamination is probed and discussed. Chapter Four details a range of new bisimidazoline ligands and their employment as supporting ligands on calcium. The catalytic performance of the resulting complexes in intramolecular hydroamination is subsequently analysed and discussed. Chapter Five investigates the attempted development of a total synthetic pathway to a new class of imoxazoline ligand and related issues. Chapter Six contains all experimental procedures, characterising data pertaining to all new compounds and complexes presented in this Thesis. Appendices A-K contain additional catalytic figures and tables of crystallographic data for all new crystallographically characterised compounds. Summary sheets of every literature and new compound presented mentioned in this Thesis are also included, along with copies of both printed publications resulting from this Thesis at the time of submission

Chiral calcium catalysts for asymmetric hydroamination/cyclisation

Calcium complexes supported by chiral 1,2-diamines have been shown to be efficient catalysts for the asymmetric hydroamination of amino-olefin substrates; the calcium complexes [Ca(NNR){N(SiMe3)2}(THF)] (R = tBu, iPr, Ph, 4-C6H4F) give enantioselectivities of up to 26% which marks a significant increase based upon literature precedence. The structure of [Ca(NNPh){N(SiMe3)2}(py)] has been computed with density functional methods

Modular ligand variation in calcium bisimidazoline complexes: effects on ligand redistribution and hydroamination catalysis

A series of calcium complexes supported by chiral bisimidazoline ligands have been studied in the catalytic intramolecular hydroamination/cyclisation of amino-olefins. The complexes [Ca(R-BIM){N(SiMe3)2}(THF)] (R = 4-C6H4Me, 5a, 4-C6H4F, 5b and tBu, 5c) have given competitive enantioselectivities (up to 12%) when compared to current literature studies involving calcium. Bisimidazolines offer a significant advance over similar bisoxazoline ligands, by allowing a greater structural variance through a modular synthetic pathway

First examples of structurally imposing eight-membered-ring (diazocanylidene) N-heterocyclic carbenes: salts, free carbenes, and metal complexes

A series of three chiral, expanded six-membered NHC–palladium(II) complexes was prepared with successively increased sterical demand, while retaining natural d-(+)-camphor as a chiral motif. The catalysts showed different reaction profiles in the asymmetric, intramolecular α-arylation of amides. The molecular structure of two N-heterocyclic and one nitrogen acyclic carbene palladium isonitrile complex was unequivocally determined by X-ray crystallographic analysis. The results reported herein account for a correlation of catalytic activity and enantiodiscrimination in relation to the degree of chiral substitution and steric congestion at the metal center. The modular and convergent synthetic route of these air- and moisture-stable palladium isonitrile complexes underlines the usefulness of this approach

Transport: challenging disabling environments

This article brings together the concerns of environmental and disability movements through examining the role of transport. Both movements critique current transport policy and practice. The disability movement has analysed how it marginalises the needs of disabled people, while environmentalists argue current transport trends are unsustainable and marginalise alternatives. Although these critiques operate independently and even seem opposed to each other, a common agenda can be developed through extending the social model of disability. The social model can be used to understand how car-dominated transport systems can be understood as disabling populations larger than those conventionally recognised as “disabled�. The car offers the technological fix of enabling abilities, in particular speed and strength, but in practice disables in a number of ways. Urban sprawl and traffic increase barriers to participation and access for many both “able-bodied� and “disabled�, while car dominance damages social interaction and limits sensory perception. Furthermore, the car economy is a major cause of impairment through crashes and physical inactivity. Understanding these together requires integrating the social model of disability with an eco-social model of impairment. This can show how unequal forms of social organisation are embodied in people and environments to produce patterns of impairment, disability and disadvantage. Finally we suggest policies to move towards sustainable societies with increased opportunities for broader social participation. The article argues that the two movements can create and benefit from a shared vision of socially inclusive, low-energy, sustainable transport