This thesis describes investigations into tandem catalysed synthesis of polycyclic heteroatom containing molecules and the utilisation of high throughput screening (HTS) methodologies to identify active catalysts. Methodology for the high throughput screening of in situ generated metal complexes as catalysts was developed. UV spectroscopy and Capillary Electrophoresis (CE) were developed as effective methods of screening combinatorial arrays of complexes as catalysts. HTS methodologies were applied to the screening of in situ generated complexes as catalysts for the hydroamination of 2-(2-phenylethynyl)aniline. Two complexes were identified to be highly active hydroamination catalysts in acetone; the in situ combinations of [Rh(CO)2Cl]2/mesBIAN 38/NaBF4 and Ir(COD)Cl]2/NaBF4. Also identified in this work was the formation of the unusual N-(2-methylvinyl)-2-phenylindole catalysed by [IrCp*Cl2]2/NaBF4 from 2-(2-phenylethynyl)aniline via the incorporation of one molecule of acetone. Complexes of the type [Cp*MCl(N-N)][X] were synthesised (M = Rh(III) / Ir(III)), N-N= bpm 31, bim 32, dmbpm 61, bik 62, mesBIAN 38 and mesim-mim 63, X= Cl-, BF4-, [Cp*MCl3]-). Where N-N was bpm 31 or bim 32 and there was no alternate counterion present, bimetallic complexes formed containing the counterion X= [Cp*MCl3]-. The three dimensional, solid state, structures of the cationic fragments of the bimetallic complexes [Cp*MCl(N-N)][X] (M= Ir, X= [Cp*IrCl3]-, N-N= bpm 31 and bim 32; M= Rh, X= [Cp*RhCl3]-, N-N= bpm 31; M= Ir, X= BF4 -, N-N= bim 32, mesBIAN 38 and mesim-mim 63) are presented. Abstraction of the chloride, in complexes of the type [Cp*IrCl(N -N)]BF4, by AgBF4 created active catalysts in situ with the best catalyst in the series for the hydroamination of 2-(2-phenylethynyl)aniline [Cp*IrCl(mesBIAN)]BF4/AgBF4. Investigations performed into the synthesis of N-(2-methylvinyl)-2-phenylindole catalysed by [IrCp*Cl2]2/BF4- have shown that the most likely potential mechanism proceeds via the initial catalysed formation of the imine followed by metal promoted cyclisation. The isolation of the complex [IrCl2(2-(2-phenylethynyl)aniline)Cp*] and investigation into its reactivity showed it to be a potential reactive intermediate in the catalytic cycle. Investigation into catalysed C-C bond formation of N-propargylindole identified the in situ generated complex [Rh(CO)2Cl]2/PPh3 as a catalyst for the generation of pyrroloquinoline as a 1:1 mixture of regioisomers.

Thesis (Ph.D.)--Aberdeen University, 2009. / Title from web page (viewed on Mar. 30, 2010). Includes bibliographical references.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

This thesis discusses the synthesis of new organic, heterocyclic materials for potential application as pigments. Chapter 1 comprises an introduction to the field of pigment and dye chemistry, discussing the rudimentary elements of colour theory, before advancing to a review of the pertinent literature regarding high performance organic pigments. In particular, the development of 1,4-diketopyrrolo[3,4-c]pyrrole (DPP) pigments is described and the central objective of synthesising alkenyl-DPPs is outlined. Chapters 2 and 3 describe synthetic efforts towards alkenyl-DPPs, employing retro Diels-Alder methodology. The reactions involving the furan-acrylonitrile adduct as the nitrile component in the standard DPP synthesis led mainly to aromatisation of the bicyclic system and the cyclopentadiene-acrylonitrile adduct failed to react altogether. The explanation for this failure has been investigated. In the course of this these studies, several DPPs incorporating a secondary alkyl substituent were prepared, not least a novel cyclohexenyl-DPP. Chapter 4 describes the use of α β-unsaturated nitriles in the standard DPP synthesis. These behaved as Michael acceptors and in the case of cinnamonitriles led to a new family of coloured materials, namely substituted 4-hydroxy-2/7- cyclopenta[c]pyrrol-1-one-5-carbonitriles. Chapter 5 describes the corresponding reaction of cinnamate esters, but in these cases bicyclic systems were not formed. The reactions are analogous to Claisen acylations and the stereochemistry of the products varied according to the substituents. Chapter 6 contains the detailed experimental work for these investigations and concludes with a portfolio of X-ray structural data.

The original aim of this project was to investigate the possibility of synthesising a novel polymer system combining the best features of cyanate ester resins and epoxy resins. Chapter 1 presents the historical background for both types of resin. The remaining three chapters describe attempts to achieve this aim by a) finding a cyanate ester that cures at a lower temperature than those in current commercial use (Chapter 2); b) using mixed epoxy and cyanate ester resins (Chapter 3); and c) designing chemically completely novel polymers from knowledge of the existing ones (Chapter 4). In Chapter 2 it was revealed that different cyanate esters cure at different temperatures, but that no obvious correlation exists between curing temperature and either steric or electronic effects of the ring substituents. The mixing of two dicyanate esters, one of which cures at a lower temperature than the other, leads to some reduction in the overall curing temperature required, but not sufficient to warrant further study at this stage. In Chapter 3 the usefulness of a previously proposed co-reaction between cyanate esters and epoxides was examined. Previous work in this area is full of inconsistencies that put many of the proposed conclusions in doubt. Further examination of the alleged co-reaction reveals that any such co-reaction is unpredictable, can vary significantly with reaction conditions and is in any case a minor reaction pathway by comparison with the self-reactions of the two individual reactants. It was therefore decided that further pursuit of this strategy was also likely to prove unrewarding in the short term. In Chapter 4 a study was made into the effects of including novel monomers in a standard epoxy resin system. These novel monomers had a cyanurate backbone with epoxide functionality, and can be cured at the lower temperatures of epoxy resins. Tests on the properties (mechanical, dielectric, water absorption, fracture toughness etc.) of these polymers were of a preliminary "scouting" nature, but are sufficiently promising to encourage further study.

The thermal decomposition of 2,3,4,5-tetraphenyldiazocyclopentadiene in the presence of carbene acceptors having Group V and VI elements to give 2,3,4,5-tetraphenylcyclopentadienylides has been extended and the first example of a telluronium ylide has been prepared by this method. The procedure has also been extended to other substituted diazo-cyclopentadienes and various new phosphonium, arsonium and sulphonium ylides have been prepared. The reaction of diazocyclopentadienes with triphenylphosphine to give either phosphazines or phosphonium ylides has been studied and the reasons for the difference in reactivity of these diazo-compounds has been clarified to some extent. It has been shown that for phosphazine formation both lack of steric hindrance and the absence of an electron- donating group on the cyclopentadiene ring are required. The thermal reaction of diazocyclopentadienes is assumed to proceed via a carbene-type intermediate which is then attacked by the reagent present to give an ylide. This reaction can be catalysed by the presence of copper-bronze and, in this case, can be effected either under melt conditions or in solution. The stability of the carbenoid intermediate is demonstrated by its preferential reaction with triphenylarsine rather than with benzene, which is present as the solvent. The reaction of 2,5-diphenyldiazocyclopentadiene with triphenylarsine gives a rearranged 2,4-disubstituted product. The carbene-type intermediate in this case is presumed to rearrange before reaction with the triphenylarsine. Some cyclopentadienylidene triphenylphosphazines have been shown to decompose thermally in the presence of triphenylphosphine to give the related triphenylphosphonium ylides. Diazocyclopentadienes have been found to react with either hydrochloric or hydrobromic acid to give the monochloro or monobromo cyclopentadienes. The parent, unsubstituted triphenylarsonium cyclopentadienylide has been prepared by the reaction of triphenylarsine with dibromocyclopentene and basification of the bis-arsonium salt so formed. Its properties and reactions have been studied and are found to be similar to the analogous triphenylphosphonium ylide. The salt method for the preparation of cyclopentadienylides has also been investigated. Triphenylarsine has been shown to react with 5-bromo-1,2,3-triphenylcyclopentadiene in solution at room temperature to give the hydrobromide salt of the ylide. Various sulphides also reacted with the bromo-compound to give, in most cases, unexpected products. The reactions of the cyclopentadienylides prepared with aldehydes have been investigated and the results are in line with previous findings. The cyclopentadienylides also readily undergo electrophilic substitution on the five-membered ring. The reaction proceeds preferentially at the 2(5)-position.

No description available.

Nitrogen heterocycles are present in nearly 60% of all small-molecule drugs approved by the US Food and Drug Administration. New innovative methods that streamline the synthesis of such heterocycles are therefore highly desirable. The use of new or underdeveloped reactive intermediates provides an excellent opportunity to develop novel heterocyclic syntheses. For example, nitrogen-substituted isocyanates (N-isocyanates) are a class of rare amphoteric isocyanates with high, but severely underdeveloped synthetic potential. The research efforts presented in this thesis have been directed towards the use of such intermediates for the rapid construction of heterocycles using cascade reactions. Using an in situ generation approach from masked (blocked) isocyanate precursors, we were able to control the homo dimerization of these species and design several cascade reactions forming more than 10 different classes of heterocycles using appropriate nitrogen nucleophiles. Given the importance of the N-N-C=O motif in pharmaceuticals and agrochemicals, N-isocyanates provide the opportunity to synthesize highly desirable cores for different industrial applications. To illustrate the potential of this new tool in heterocyclic chemistry, more than 200 heterocycles were synthesized using this methodology. In Chapter 2, heterocycles incorporating only one atom from the N-isocyanate will be presented. More precisely, the first cascade reaction involving N-isocyanates for the rapid synthesis of saturated heterocycles will be presented. The incorporation of 2 atoms within the ring will then be discussed in Chapter 3 with the synthesis of hydantoins, imidazolones, thiazolines, pyrazoles and phthalazinones. Chapter 4 will focus on the incorporation of every atom in the heterocycle to form other bioactive cores such as azauracils, pyridazinones and azadiketopiperazines. Lastly, Chapter 5 will describe our efforts for the synthesis of acyclic molecules such as semicarbazides and aza-peptides.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / toc / Chemistry / Master / Master of Philosophy