A new system for catalytic asymmetric epoxidation
thesisposted on 28.06.2018, 09:12 by Adel Ardakani
This thesis discusses the field of asymmetric synthesis of oxiranes. An introduction highlighting the most successful methods for the synthesis of chiral epoxides including the latest advances in these areas, with particular attention paid to the organocatalytic techniques is presented in chapter one. The second chapter begins by summarizing the group's previous efforts in the initial stage of this project and sets the motif for this work. These include: the synthesis of enantiopure dihyroisoquinolinium salts with a chiral residue attached to the exocyclic carbon-nitrogen bond as catalysts for asymmetric epoxidation; utilizing systems such as camphor and natural amino acids as starting points for these syntheses; developing other catalyst families in order to delve into the possibility of eliminating the structural weaknesses leading to loss of enantioselectivity in the oxygen transfer process; attempts to probe the reactive intermediates responsible for the asymmetric induction by analytical techniques; checking for catalyst applicability with different alkene and sulphide substrates; the development of anhydrous reaction conditions and their testing with the successful catalysts prepared. Enantiomeric excesses of up to 70% have been obtained. An attempt at exploring the synthesis of chiral reagents for the asymmetric epoxidation via a Payne/peroxyacid route is also described. This chapter concludes with a comparison of the catalyst families generated, and presents a few suggestions for future research in this area. The third chapter is dedicated to, the experimental section and includes the methods of synthesis and characterization of the compounds in the results and discussion chapter. There are three appendices at the. end of the thesis; Appendix A contains a summary the X-ray reports regarding the crystallographic data of the compound structures presented in chapter two. Appendix B contains samples of the analytical spectra of the enantiomeric excess determination for epoxides. Appendix C includes a copy of both publications I was involved in during my research in this topic.
Loughborough University. [EPSRC and] AstraZeneca plc (CASE Award Studentship).