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Title: Synthesis of oxygen containing functionalities : use of the acyloin and metathesis reaction in organic chemistry
Author: Jahanshahi Esfahani, Ali
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2012
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Abstract:
1. In the first part of this thesis, the concept of a tether based intramolecular crossed -acyloin reaction mediated by heterogeneous lithium/ 4,4' -di-teti-butylbiphenyl (Li/DBB) reducing conditions was examined. The objective of the project was to accomplish an intramolecular crossed-acyloin reaction, by employing non-symmetric di-esters, linked with a suitable tether (diol) between the two acyl functionalities. Chapter 1: Introduction - Acyloin Condensation. The concept of carbon-carbon coupling reactions between two carbonyl functionalities to synthesise a-hydroxyketone (acyloin) moieties is described. Generally, there are two methods, either by bimolecular reductive coupli ng of esters, known as acyloin condensation or the umpo/ung dimerisation of aldehydes, known as benzoin condensation. The background and recent developments in these reaction categori es are discussed in this section. In addition, this section outlines the project's aims and describes the previous work conducted in the group. Chapter 2: Results & Discussion - An Alternative Route to Crossed-ocyloin In this section, the tether based intramolecular crossed-acyloin reaction mediated by Li/DBB reducing conditions is introduced. This work is based on the hypothesis that a suitable tether, could promote an intramolecular crossed-acyloin reaction. The objective was successfully achieved through a series of competition experiments, which demonstrated that the application of exo-exo norbornenediol as a tether exclusively formed crossed-acyloin products. This discovery was accompanied by an investigation into regi oselective crossed-acyloin reaction. 2. In the second part of this thesis, the Sharpless Asymmetric Epoxidation (SAE) desymmetrisation reaction of O'-symmetric diene 1,3-diols was exami ned. It was suggested that formation of the epoxide would trigger a stereoselective 5-exo-tet ring closure to deliver predominately trans-THF adducts. Chapter 3: Introduction - Metal Mediated Synthetic Routes to trans-2,5-Disubstituted THFs This section introduces the transition metal mediated cyciisation of bishomoallylic alcohol, to the corresponding trans- THF moieties. In particular, the development and application of three methods were highlighted; rhenium mediated (3+2) oxidative cyclisation, cobalt catalysed oxidative cyclisation and an rc-allylpalladium complex catalysed reaction. In addition, the concept of the Sharpless Asymmetric Epoxidation (SAE) is introduced and the project objectives are outlined. Chapter 4: Results & Discussion - A NOJel Route Towards trans- THFs The primary effort was to design a robust route to form the test substrate, (3R,55}hepta-1,6-diene- 3,5-diol, which was accomplished in good yield by Ring Opening/Crossed metathesis (ROM) of silyl ether protected (1 R, 35 }cyclopent-4-ene-1,3-diol. The expe rimental results have demonstrated that SAE of the diene 1,3 diol formed trans-THF. Chapter 5: Experimental Full experimental procedures and characterisation of the synthesised molecules are reported.
Supervisor: Donohoe, Timothy J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.559765  DOI: Not available
Keywords: Acyloin reaction ; Metathesis (Chemistry)
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