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Novel selenium-mediated cyclisations

Shahzad, Sohail Anjum 2010. Novel selenium-mediated cyclisations. PhD Thesis, Cardiff University.

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Abstract

The present work describes the selenium-mediated cyclofunctionalisations of alkenes. Three different areas are reported herein. Chapter 2 reports syntheses of several substrates for carbocyclisation reactions and use of selenium and Lewis acids resulting in various dihydronaphthalenes. These dihydronaphthalenes then acted as substrates for second ring forming reactions. This novel tandem double cyclisation comprises a carboannulation, a Friedel-Crafts reaction and a rearrangement. This cascade sequence has been proven to be a useful tool in the selective synthesis of dihydronaphthalenes and benzofluorenes from easily accessible stilbenes and provides fast access to polycyclic ring systems in a single step. Chapter 3 describes electrophilic selenium-mediated reactions which have been used to cyclise a range of /-keto esters to corresponding biaryl compounds under very mild conditions. The products were formed by a carboannulation via addition/elimination sequence and a subsequent rearrangement of range of alkyl and aryl groups. The key starting materials stilbene /-keto esters were readily prepared by Heck coupling and hydrolysis followed by condensation with potassium ethyl malonate. Chapter 4 describes work on catalytic selenium reagents with stoichiometric amount of hypervalent iodine to convert a range of stilbene carboxylic acids into their corresponding isocoumarins. The work also describes the selective synthesis of dihydroisocoumarins using diphenyl disulfide and dimethyl diselenide.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
ISBN: 9781303195778
Funders: Higher Education Commission of Pakistan, Cardiff University
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 23:29
URI: http://orca-mwe.cf.ac.uk/id/eprint/54389

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