A novel cyclization in the construction of fused rings

Banjoko, Oluwakemi Oluwabunmi (2011) A novel cyclization in the construction of fused rings. Doctoral thesis (DPhil), University of Sussex.

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The discovery of the novel thermal cyclization of enediyne molecules within the
Parsons group during studies directed towards the total synthesis of lactonamycin has
stimulated an intense research into the cyclization of the enediynes.
In this research different functionalised enediynes were synthesised to investigate:-
(i) the scope and limitations of the thermal cyclization reactions,
(ii) the proposed biradical mechanism for the cyclization reactions,
(iii) the intermolecular trappings of the proposed biradical, and
(iv) the effect of sterically demanding groups on the rate of cyclization.
In the process of testing these objectives, we have been able to synthesize highly
functionalised heterocyclic rings by simple thermal cyclization reactions without using
any metal catalyst. We have discovered that the cyclizations may have involved free
radical mechanism or an ene reaction, followed by a Diels – Alder cycloaddition
reactions. Interestingly the cyclised compound 2.1 shows two stereogenic centres at C2
and C4 with an absolute configuration of R and S respectively. An in-depth exploration
of the stereochemistry of these reactions may increase their application in controlling
the stereochemistry of ring systems through simple metal free thermal cyclization
reactions. Confirmation of the specific mechanism constitutes an ongoing research
within the Parsons group. Conclusively cyclization of highly functionalised enediynes
had been proved to be a versatile route to the synthesis of diverse heterocyclic
compounds. The ease of cyclizations of a majority of the enediynes in this study has
shown that functionalisation and diversification of the core enediyne systems could be
utilized in the synthesis of pharmaceutically important antitumour drugs.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Life Sciences > Chemistry
Subjects: Q Science > QD Chemistry
Q Science > QD Chemistry > QD0241 Organic chemistry
Depositing User: Library Cataloguing
Date Deposited: 17 Jun 2011 09:40
Last Modified: 14 Aug 2015 12:47
URI: http://sro.sussex.ac.uk/id/eprint/6894

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