Asymmetric syntheses of various novel chiral ligands with norbornene backbone : the use of chiral catalyst in asymmetric reactions


Thesis Type: Doctorate

Institution Of The Thesis: Middle East Technical University, Faculty of Arts and Sciences, Department of Chemistry, Turkey

Approval Date: 2005

Thesis Language: English

Student: Olcay Elmalı

Supervisor: CİHANGİR TANYELİ

Abstract:

The synthetic strategy of this study mainly depends upon the asymmetric desymmetrization of meso norbornene type an anhydride. Asymmetric desymmetrization was achieved by using chinchona alkaloids under kinetically controlled conditions. The resultant mono ester carboxylic acid was epimerized to trans configuration. Subsequent esterification followed by lithium aluminum hydride reduction afforded the first chiral diol ligand with 98 % ee. Transformation of diol to corresponding trans diamine was achieved via Mitsunobu-Gabriel combination. The resultant diamine was first transformed into salen type ligand with 3,5-di-tert-butyl-2-hydroxybenzaldehyde. Throughout this process, no racemization was observed and all the ligands tested in asymmetric reactions have 98 % ee value. The second part of the thesis involves the asymmetric test reactions of the chiral ligands to check the effectiveness of them. The first testing method was diethylzinc addition to benzaldehyde. The ligands showed moderate effectiveness. The salen type ligand was tested in asymmetric epoxidation and aziridination reactions and it showed good effectiveness. Another applied method was desymmetrization of meso 2-cyclohexene-3,4-diol in which 2-(diphenylphosphino)benzoic acid attached trans-diol and trans-diamine type ligands were tested. Since norbornene type strained bicyclic systems are available in ring opening methathesis polymerization (ROMP) reactions, trans-diamine was subjected to ROMP to get an enlarged macromolecular system