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Title: Beyond C-H activation : the preparation of novel heterocycles using catalytic dearomatisation
Author: Sankey, Rosalind Fay
ISNI:       0000 0004 2724 4267
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2011
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The continuous drive for efficient bond forming reactions has led to the emergence of C-H activation methodologies. More specifically, direct arylation reactions are commonly employed in the synthesis of a range of heteroaromatic products. The latter make up a considerable proportion of medicinally important compounds and therefore their rapid and efficient synthesis is paramount. The preparation of carbazoles has been extensively developed within the Bedford group. The expansion of this palladium-catalysed intramolecular direct arylation methodology has been explored with the aim of producing interesting heterocycles, namely acridans and acridines. Interestingly, instead of the expected C-H activation reaction, an unprecedented catalytic dearomatisation reaction took place. This was developed into a more general methodology to produce a range of novel heterocycles, including 4a-alkyl-4aH- carbazoles and dihydroindolo[2,3-b]indoles. Due to their instability these heterocycles undergo a range of interesting transformations, including dimerisation, dealkylation and hydro lysis reactions. Furthermore, it was proposed that typical direct arylation reactions could be occurring via a catalytic dearomatisation mechanism rather than one of the more generally accepted C-H activation mechanisms. A detailed kinetic study has been carried out. Although evidence to support a dearomatisation mechanism could not be obtained, the turnover-limiting step for two substrates could be proposed and a number of interesting observations made.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available