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Heterogeneous asymmetric aziridination of styrene using Cu 2+-exchanged zeolite Y.

Ryan, Darragh Joseph. 2006. Heterogeneous asymmetric aziridination of styrene using Cu 2+-exchanged zeolite Y. PhD Thesis, Cardiff University.

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Abstract

The synthesis of pure enantiomers using catalytic processes continues to receive considerable research attention. The aziridination of olefins is an important reaction in organic synthesis as the aziridines formed are precursors to pharmaceuticals and agrochemicals. Aziridines can be synthesised by many synthetic routes, the most relevant being the homogeneous catalytic formation of aziridine demonstrated by Evans. A heterogeneous system was further developed, catalysed by copper-exchanged zeolite Y and using bis(oxazoline) as chiral modifier. Ns N0'rN=i-O ' A R O J Me. Me / 88% yield N / 86% ee Plf Sh Scheme A: Aziridination of styrene using PhI=NNs The copper-catalysed aziridination of styrene and styrene derivatives using either Cu(OTf)2 as a homogeneous catalyst or copper exchanged zeolite Y modified as a heterogeneous catalyst with bis(oxazoline) using N-(p-nitrophenylsulfonyl)imino phenyliodinane (PhI=NNs) as nitrene donor was carried out. Detailed time on line profiles (TOL) for the progression of the reaction was monitored revealing high chemical yields and enantioselectivities (Scheme A). In this study, C2-symmetric Cu-bis(oxazoline) complexes were used to catalyse styrene-using N-(p-tosylsulfonyl)imino phenyliodinane (PhI=NTs) as nitrene donor. The course of the reaction was investigated by EPR and UV-Vis spectroscopy and was supported by catalytic studies carried out studies in order to reveal how the chirality of the formed Cu-bis(oxazoline) complex was crucial for the overall enantioselectivity and yield of the aziridination reaction. During the aziridination of styrene using copper bis (oxazoline) complexes the ee increases with conversion due to further reactions of the product. Kinetic resolution experiments were carried out to investigate the mechanism involved, the effect of adding reaction breakdown products and the major product, aziridine to the reaction and also to investigate the shape of the reaction profile and its rate of reaction.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
ISBN: 9781303182334
Date of First Compliant Deposit: 30 March 2016
Last Modified: 10 Jan 2018 05:23
URI: http://orca.cardiff.ac.uk/id/eprint/55704

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