Chapter One of this Thesis reports an investigation of the synthesis of diterpenoids (as potential ligands for cyclomanganation reactions) from podocarpic acid, and one from dehydroabietic acid. A number of monocyclic aromatic and chalcone derivatives were synthesised to act as model compounds in the subsequent complexation reactions. The second chapter describes successful complexations of the above ligands containing aldehyde, ketone, ester, or oxime groups as directing functionalities to form the resulting tetracarbonylmanganese sigma adducts in moderate to excellent yield. Attempted complexation of amide-containing ligands proved generally to be unsuccessful. Complexation of ligands containing either two potential sites for manganation or two potential ligating groups were investigated and the structures of the isolated complexes established unequivocally by N.M.R. spectroscopy or by X-ray crystallography. Chapter Three describes the successful coupling reactions of the tetracarbonylmanganese complexes with ethene and with substituted electron-poor olefins to give pentaannulated derivatives of podocarpic acid in very good yields. The stereochemistry of two cyclised alcohols was assigned unambiguously by single-crystal X-ray diffraction experiments. Various methods of activating the tetracarbonyl complexes were investigated, including chemical oxidation, and palladium(II)-mediated or thermally-promoted reactions. Two of the pentaannulated adducts were converted successfully into benzannulated analogues in good yield. Analogous coupling reactions of the activated complexes with ethyne and substituted alkynes are discussed in Chapter Four. Chapter Five reports an investigation of the reactions of the tetracarbonylmanganese complexes with halogen electrophiles such as Br2, ICl, or ICl3. When these reactions were performed in non-protic solvents the corresponding aryl halides were isolated in moderate to excellent yield. However, in protic solvents carbonyl insertion occurred to afford γ-lactones in very good yield. The stereochemistry of one of these lactones was assigned unambiguously by a single-crystal X-ray diffraction experiment. Oxidative cleavage of the C-Mn bond with a number of reagents proved generally to be unsuccessful, the isolation of oxygenated diterpenoids being observed only from reaction with Pb(OAc)4. Chapter Six describes various attempts at functionalising ring C of podocarpic acid derivatives via alternative methods to cyclomanganation. These include an investigation into the formation of η4-dienol ether and η4-diene tricarbonyliron complexes derived from the Birch reduction products of podocarpic acid derivatives; attempted regioselective chlorination and mercuration studies of ring C arenes; functionalisation of chlorinated podocarpic acid derivatives via their tricarbonylchromium complexes; and attempted oxidation of ring C arenes with meta-chloroperbenzoic acid.
| Identifer | oai:union.ndltd.org:ADTP/276014 |
| Date | January 1991 |
| Creators | Metzler, Michael Reinhold |
| Publisher | ResearchSpace@Auckland |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated., http://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm, Copyright: The author |
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