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5-endo-dig approaches to pyrroles

Singkhonrat, Jirada 2004. 5-endo-dig approaches to pyrroles. PhD Thesis, Cardiff University.

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This project required developing new practical routes towards pyrroles and could help the project of total synthesis of (-)-rhazinilam. In chapter one, the most widely used methods for constructing the pyrrole ring system are reviewed. The origins of this project were to investigate further uses for the iodocyclization reactions developed previously. In chapter 2, a new approach to such highly substituted pyrroles in which the key step is a 5-endo-dig halocyclisation of substituted homopropargylic sulfonamides was successfully achieved. Key to the success of this novel method is the rapid preparation of suitable starting materials, from 1-alkynes by sequential formylation and condensation with a tin(II) enolate of vV-tosyl glycinate. Also, in chapter 2, a transition metal-catalyzed cyclisation using silica-supported silver nitrate was investigated and found to be effective. The reaction is clean and proceeds in quantitative yields. Obviously this fundamental research project is of a great interest because (-)-rhazinilam acts as an antimitotic agent like taxol, which are powerful anticancer agents. Different strategies of this approach are reviewed in chapter 3. In chapter 4 and 5, various aspects of separate approaches to the anti-tumor compound rhazinilam are described. In the former, both the synthesis of suitable 3-arylpyrrole cores and strategies for extending this methodology by the incorporation of a suitable substituent based on a cleavable cyclohexene are outlined. In the second section, chapter 5, similar issues are addressed but, in contrast, the Ag(I) methodology is used to construct a suitable arylpyrrole, the synthesis of which also features construction of the key precusor by aziridine ring hydrolysis. An efficient route to an enantiopure precusor of the necessary side chain is also described. This thesis is completed by a full experimental section and reference list.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
ISBN: 9781303200496
Funders: EPRSC, Royal Thai Government
Date of First Compliant Deposit: 30 March 2016
Last Modified: 10 Oct 2017 15:29

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