Use this URL to cite or link to this record in EThOS:
Title: Synthesis of new chiral N-heterocyclic carbenes and abnormal carbenes
Author: Levy, Jean-Noel
ISNI:       0000 0004 2699 1279
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2011
Availability of Full Text:
Access from EThOS:
Access from Institution:
Chapter 1 Carbenes have fascinated organic chemists ever since the first evidence of their existence. The isolation and first crystallographic analysis of a stable NHC by Arduengo, in 1991, has had a major impact on the application of NHCs in chemistry. NHCs are widely used as ligands for transition metals, but also as catalysts in their own right. The aim of this project is to synthesise novel monodentate chiral NHCs 1 in order to induce a high level of stereocontrol in a selection of asymmetric reactions. The rigid ring structure, C2 symmetry and the presence of bulky groups (R) that project directly toward the reactive centre are important concepts in the design of our molecules. During the first part of my thesis, we developed a one-pot synthesis of allylic chlorides from benzaldehyde. A mechanistic study was carried out, as well as studying the scope of the reaction. We then achieved the synthesis of the desired NHCs precursors in 13 or 14 steps and carried out studies of their coordination and application in asymmetric α-arylation and allylic alkylation. Chapter 2 Recently novel coordination modes have been noted for NHCs. The so-called “abnormal” NHCs, due to their isomeric relationship between C2- and C4-bound imidazolylidene ligands are one type of relatively unexplored ligand. We have therefore developed a strategy to access chiral abnormal NHCs. Two different chiral abnormal NHC precursors: 1,2,3-triazolidinenes 2 and isomeric Hartwig’s NHCs 3 were synthesised via a short synthesis (2 or 3 steps) and metallated with a transition metal.
Supervisor: Fuchter, Matthew Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral