Metal-mediated intramolecular hydroamination and hydro(acy)alkoxylation reactions

• Main Author: Arbour, Jannine Louise
• Other Authors: Hii, Mimi
• Published: Imperial College London 2012
• Subjects: 547.4
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544267

This PhD thesis describes work undertaken to effect asymmetric catalysis in hydroamination and hydro(acy)alkoxylation reactions of allenes. The introductory Chapter provides an overview of recent advances in asymmetric heterofunctionalisation reactions of allenes. This includes intra- and inter-molecular reactions involving C-N and C-O bond formations. Chapter 2 begins by comparing the preparation of a γ-allenic alcohol by two different synthetic routes and its subsequent use in intramolecular hydroalkoxylation reactions using copper(II) and silver(I) salts. From this study, the ability of silver diphosphine complexes to facilitate enantioselective hydroalkoxylation reactions in a 5-exo-trig fashion was discovered. Extensive reaction optimisation was undertaken, however only moderate ee’s and conversions were observed. In Chapter 3, the use of other metal Lewis acids to catalyse hydroalkoxylation reactions of γ-allenic alcohols is presented. DFT calculations undertaken by a colleague (Prof H. S. Rzepa) were used to rationalise the observed regioselectivities with silver(I), zinc(II), and tin(II) triflates. From DFT calculations, the metal counteranion was found to be intimately involved in the C-O bond formation. In the following two Chapters, the possibility of asymmetric synthesis by using chiral anionic ligands is discussed. In Chapter 4, additional γ-allenic alcohols and β-allenic acids were synthesised for intramolecular hydroalkoxylation or hydroacyalkoxylation reactions respectively. In Chapter 5, the respective γ-allenic amines were prepared for intramolecular hydroamination. In both cases, the outcome, scope and limitations of the reaction are discussed. In Chapter 6, an overall conclusion and future work is discussed. The last Chapter contains experimental procedures and characterisation data of all the compounds synthesised during the course of this project.