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by Wai Him Kwok. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.

M.Sc. / The aim of this project was the synthesis of viridamine analogues, to be used for selective metal complexation. This, therefore, required the synthesis of diketopiperazines, containing an imidazole-type side chain. The imidazole functionality was introduced into the synthesis via peptide acid coupling reaction between histidine and another amino acid. Before any coupling reactions were possible it was necessary to protect the carboxylic acid functionality of one of the two amino acids being used and the amine functionality of the other. This was to prevent mixed products forming. Owing to the continued difficulty at achieving selective N-protection of histidine, it was decided to make use of the corresponding methyl ester instead. After some initial attempts, it was found that the methyl ester of histidine, which was bought as the dihydrochloride salt, could be readily coupled to a variety of Boc protected amino acids. The Boc protected amino acids could be prepared under various conditions using di-tertbutyl dicarbonate. A range of conditions was investigated for the coupling of the two amino acids, i.e. the histidine methyl ester dihydrochloride and a Boc protected amino acid. Successful coupling was finally achieved using tetrahydrofuran as solvent, N-hydroxy benzotriazole as reaction promoter, N-methyl morpholine as a base and dicyclohexylcarbodiimide as the coupling agent. After varying the reaction conditions the optimised reaction conditions gave yields in the region of 76%. Once coupling had been achieved, it remained to cyclise the dipeptide. Cyclisation was preceded by the removal of the Boc protecting group either in situ or in a two step process. In the absence of the imidazole functionality, removal of the Boc group was readily achieved using trifluoroacetic acid. However, attempted deprotection of dipeptides containing the imidazole functionality led to decomposition of the dipeptide under identical conditions. It was therefore necessary to find an alternative form of deprotection. This was found in the form of formic acid, which proved to be successful in removing the Boc group and in effecting cyclisation to the analogous diketopiperazine. This particular form of in situ cyclisation proved to be very low yielding. This problem was circumvented by following the formic acid treatment by a period of reflux in a toluene I 2-butanol mixture. Cyclisation was effected with pure products being obtained in high yield, after column chromatography. Complexation reactions were initiated with the synthesised diketopiperazines but unfortunately no X-Ray diffraction studies could be carried out, due to the formation of amorphous solids instead of crystalline materials.

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

The synthesis and characterization of pyridinyl &alpha / -diimine Pd(II) complexes having a functionalized hydrocarbon attached to the imino nitrogen was performed. The catalytic activity of these complexes were then evaluated in the polymerization of ethylene and in the Heck coupling reaction of methyl acrylate with iodobenzene.<br /> <br /> Unconjugated &beta / -diimine complexes of palladium were also synthesized and their activities towards ethylene polymerization and the Heck coupling of methyl acrylate and iodobenzene also evaluated and compared to that of the &alpha / -diimine complexes. Three of the &alpha / -diimine complexes synthesized showed activity towards ethylene polymerization, these being the complexes bearing the allyl, styrene and phenol functionalities. &omega / -Carboxylato complexes which were also synthesized showed no activity towards ethylene polymerization.<br /> <br /> The polymer produced was found to be high density linear polyethylene with an average PDI of 2.54 with Mn values ranging between 3.42 and 6.90 x 10-5 and Mw values ranging between 6.05 and 17.6 x 10-5.<br /> <br /> The complexes bearing the allyl, styrene and phenol functionalities, as well as the &omega / -carboxylato complexes active in the Heck coupling reactions of methyl acrylate with iodobenzene. None of the unconjugated &beta / -diimine complexes prepared showed any activity towards ethylene polymerization even at high Al/Pd ratios. The activity of these complexes towards the Heck arylation reaction was comparable to that of the &alpha / -diimine complexes showing similar activities.

by Chi-Hang Lee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 71-80). / Abstracts in English and Chinese. / ABSTRACT --- p.i / ACKNOWLEDGMENT --- p.iv / TABLE OF CONTENTS --- p.v / LIST OF SCHEMES --- p.vii / LIST OF FIGURES --- p.viii / LIST OF TABLES --- p.x / ABBREVIATIONS --- p.xi / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Discovery of Phthalocyanines --- p.1 / Chapter 1.2 --- Synthesis of Phthalocyanines --- p.4 / Chapter 1.2.1 --- Metal-Free Phthalocyanines --- p.4 / Chapter 1.2.2 --- Metallophthalocyanines (MPcs) --- p.5 / Chapter 1.2.3 --- Sandwich Complexes (MPc2) --- p.7 / Chapter 1.2.4 --- Tetra-Substituted Phthalocyanines --- p.8 / Chapter 1.2.5 --- "2,3,9,10,16,17,23,24-Octa-substituted Phthalocyanines" --- p.11 / Chapter 1.2.6 --- "1,4,8,11,15,18,22,25-Octa-substituted Phthalocyanines" --- p.12 / Chapter 1.3 --- Mechanism for Phthalocyanine Formation --- p.14 / Chapter 1.4 --- Purification of Phthalocyanines --- p.16 / Chapter 1.5 --- Characteristics of Phthalocyanines --- p.17 / Chapter 1.5.1 --- Electronic Structure --- p.17 / Chapter 1.5.2 --- Absorption Spectra --- p.17 / Chapter 1.5.3 --- X-Ray Diffraction Studies --- p.19 / Chapter 1.6 --- Applications of Phthalocyanines --- p.20 / Chapter 1.6.1 --- Colorants --- p.20 / Chapter 1.6.2 --- Photodynamic Therapy --- p.21 / Chapter 1.6.3 --- Catalysis --- p.22 / Chapter 2 --- Results and Discussion --- p.23 / Chapter 2.1 --- "Preparation, Spectroscopic Properties, and Structure of Phthalocyanines Substituted with Four 2,4-Dimethyl-3- pentyloxy Moieties" --- p.23 / Chapter 2.1.1 --- Synthetic Studies --- p.24 / Chapter 2.1.2 --- UV-Vis Spectra --- p.28 / Chapter 2.1.2.1 --- Effects of Metal Center --- p.28 / Chapter 2.1.2.2 --- Effects of Substituents --- p.30 / Chapter 2.1.2.3 --- Effects of Concentration --- p.30 / Chapter 2.1.2.4 --- Absorption Spectra of MnClPc(OC7H15)4 (10) --- p.34 / Chapter 2.1.3 --- 1H NMR Spectra --- p.35 / Chapter 2.1.4 --- Structural Studies --- p.38 / Chapter 2.1.4.1 --- Molecular Structures of ZnPc(OC7H15)4 (3) and CoPC(OC7H15)4 (5) --- p.39 / Chapter 2.1.4.2 --- Molecular Structure of MnClPc(OC7H15)4 (10) --- p.41 / Chapter 2.2 --- Formation and Crystal Structures of Novel Inclusion Complexes of Phthalocyanines and Oxalic Acid --- p.43 / Chapter 2.2.1 --- 1:1Complex with Metal-free Phthalocyanine (8) --- p.43 / Chapter 2.2.2 --- 1:1Complexes with Palladium Phthalocyanine (4) --- p.49 / Chapter 2.2.3 --- Conclusion --- p.51 / Chapter 2.3 --- Cerium Promoted Formation of Metal-Free Phthalocyanines --- p.52 / Chapter 2.3.1 --- Introduction --- p.52 / Chapter 2.3.2 --- Preparation of Metal-free Phthalocyanines --- p.52 / Chapter 2.3.3 --- Conclusion --- p.58 / Chapter 3 --- Experimental --- p.59 / Chapter 3.1 --- General --- p.59 / Chapter 3.2 --- "Synthesis of 3-(2,4-dimethyl-3-pentyloxy)phthalonitrile (2)" --- p.60 / Chapter 3.3 --- "Synthesis of ZnPc(OC7H,5)4 (3 and 6)" --- p.61 / Chapter 3.4 --- Synthesis of PdPc(OC7H15)4 (4 and 7) --- p.62 / Chapter 3.5 --- Synthesis of CoPc(OC7H15)4 (5) --- p.64 / Chapter 3.6 --- Synthesis of H2Pc(OC7H15)4 (8) --- p.64 / Chapter 3.7 --- Synthesis of MnClPc(OC7H15)4 (10) --- p.66 / Chapter 3.8 --- General Procedure for the Cerium-Promoted Cyclization of Phthalonitriles --- p.67 / Chapter 3.9 --- X-ray Crystallographic Analyses --- p.69 / Chapter 4 --- REFERENCES --- p.71 / APPENDIX A lH and13 C̐ưث1H} NMR spectra / APPENDIX B X-ray Crystallographic Data

The synthesis and characterization of pyridinyl &alpha / -diimine Pd(II) complexes having a functionalized hydrocarbon attached to the imino nitrogen was performed. The catalytic activity of these complexes were then evaluated in the polymerization of ethylene and in the Heck coupling reaction of methyl acrylate with iodobenzene.<br /> <br /> Unconjugated &beta / -diimine complexes of palladium were also synthesized and their activities towards ethylene polymerization and the Heck coupling of methyl acrylate and iodobenzene also evaluated and compared to that of the &alpha / -diimine complexes. Three of the &alpha / -diimine complexes synthesized showed activity towards ethylene polymerization, these being the complexes bearing the allyl, styrene and phenol functionalities. &omega / -Carboxylato complexes which were also synthesized showed no activity towards ethylene polymerization.<br /> <br /> The polymer produced was found to be high density linear polyethylene with an average PDI of 2.54 with Mn values ranging between 3.42 and 6.90 x 10-5 and Mw values ranging between 6.05 and 17.6 x 10-5.<br /> <br /> The complexes bearing the allyl, styrene and phenol functionalities, as well as the &omega / -carboxylato complexes active in the Heck coupling reactions of methyl acrylate with iodobenzene. None of the unconjugated &beta / -diimine complexes prepared showed any activity towards ethylene polymerization even at high Al/Pd ratios. The activity of these complexes towards the Heck arylation reaction was comparable to that of the &alpha / -diimine complexes showing similar activities.

In this study polar ligands that would be suitable for use in homogenous catalysis in aqueous-organic and/or ionic liquid systems were designed and synthesised. Initially an attempt was made to design a synthetic route that would incorporate an imidazolium into a phosphorus compound which would then allow the variation of the alkyl group on the imidazole or of the anion, thereby producing a series of ionic ligands with wide range of anticipated chemical and physical properties. This approach was partially successful: phosphines containing imidazolium moieties were synthesised by incorporating N-methyl imidazolium into bi- and tri-aryl phosphine compounds. As these ligands contain imidazolium residues, the retention of the catalyst in the ionic liquid to be used in the catalytic transformation would be enhanced. Water-soluble ligands that are suitable to aqueous-organic systems were also synthesised. The ligands were synthesised by first performing a Michael type reaction with diphenyl phosphine and a Michael acceptor, in this case, malonate esters. These were reduced and subsequently reacted with 1,4-butanesultone. The addition of butane sultone to these phosphorus compounds made them sufficiently water-soluble and therefore ideal for catalysis in aqueous biphasic or ionic solutions. Several water-soluble/ionic ligands were synthesised by incorporating dimethylphosphoryl chloride into di- and tri-aryl phosphine ligands in high yields followed by subsequent hydrolysis of the phosphonate groups. All the ligands produce were tested in transition metal-catalysed reactions, namely the Heck reaction, the Suzuki cross coupling and the Hydroformylation reaction. Test reactions were carried out under conditions selected to show the effectiveness of the ligands in the reaction, and they were performed in organic and aqueous-organic systems, as well as in ionic liquids for the Heck reaction. The results of these reactions were compared to the benchmark triphenylphosphine and it was found that the new ligands produced results that were similar to the triphenylphosphine but there were numerous instances where the new ligands produced better results. This study, therefore allowed for the synthesis for a range of polar phosphine ligands that would be suitable for homogenous catalysis using aqueous and/or ionic liquid systems, and these ligands were shown to influence transition metal-catalysed reactions. / Prof. D.B.G. Williams

The large number of new heteronuclear bidentate ligands recently reported in the literature has unveiled a new area of research, namely that the use of different heteroatoms in bidentate ligands has led to new avenues towards more selective processes especially in asymmetric transformations. Instead of employing the traditionally used bidentate bisphosphine ligands, the dual objective of this study was therefore to design and synthesise P-N based bidentate ligands, and to apply these in catalytic transformations. A general route towards the synthesis of different series of P-N based ligands was followed. This path involved, as initial step, the condensation of o-diphenylphosphinobenzaldehyde with a series of primary amines to afford a series of iminophosphine ligands. Upon subsequent reduction of the iminophosphine ligands, a series of secondary aminophosphine analogues was obtained, and upon alkylation of the latter in the presence of a base, their tertiary aminophosphine derivatives were isolated. In these three series of ligands, the oxidation state of the nitrogen atom, as well as the degree of alkylation on this atom, was varied. These ligands were further elaborated by the incorporation of a second phosphorus atom to the already bidentate P-N ligands. This was achieved by reacting the secondary aminophosphine ligands with a base and chloro-diphenylphosphine. In order to vary the electronic nature of the newly introduced second phosphorus atom, a method for the incorporation of a dicyclohexyl phosphine moiety was developed. By introducing this group into the P-N backbone of these ligands, it was thus possible to electronically distinguish between two different phosphorus atoms in one ligand. Apart from the nature of the nitrogen and phosphorus atoms in these ligands, the use of different R-groups derived from the primary amines, enabled further variance in the inherent characteristics of these ligands: the variation in R-groups included aliphatic moieties, aromatic groups, and groups that contained additional heteroatoms. In these cases, the variation in R-groups thus also influenced the denticity of these ligands, which could render them more versatile in catalytic applications. In addition, a series of S-N based ligands, as well as some chiral P-N based ligands, was synthesised by using the previously-developed protocol. The oxygen sensitive nature of phosphines sometimes requires protection of these phosphines during different synthetic steps, and borane is often used for this purpose. However, deprotection of these phosphine ligands is required before they can be used in metal-catalysed reactions. As an adjunct to the present synthetic strategy, the concept of deprotecting phosphine-borane complexes such that new, extractable borane complexes are formed, was investigated, and formed a small part of this overall study. The deprotection of phosphine-boranes was performed using various “new” deprotecting reagents, and the borane species were separated from the free phosphines by using water / organic phase separations. The various extraction coefficients of the amine-borane complexes were determined. All the newly prepared heteronuclear ligands were used in a variety of catalytic transformations, including reactions catalysed by palladium, chromium and rhodium. The results obtained from these catalytic transformations indicated that most of these ligands afforded highly active catalysts in the different applications, and results were, in many cases, better than those obtained with commercially available ligands such as triphenylphosphine and dppp. To end off this study, an investigation towards the ó-donating properties of a selection of phosphine ligands was performed by converting the phosphines into their corresponding phosphine selenides, and calculating the 1J(77Se-31P) coupling constants. From this study, it was found that the electronic nature of different phosphine atoms in the same ligand could be characterised, and such information, in turn, can be used for the design of new ligands for specific catalytic systems. / Prof. D.B.G. Williams

The main objective of the research described in this dissertation was the preparation of a range of bulky and electron-rich phosphine ligands using the DoM methodology developed in our labs for this purpose. These ligands would be employed in the Suzuki cross-coupling reaction of deactivated aryl bromides and aryl chlorides. Initially, a range of phosphinic amides was synthesised and tested for DoM reactivity. TMSCl, MeI and O2 were successfully used as electrophiles, incorporating TMS, Me and OH groups in the ortho-position of these phosphinic amide systems. This development was encouraging and provided a route to incorporate a phosphine on the ortho-position of these phosphinic amide systems by using Ph2PCl and Cy2PCl as electrophiles to incorporate Ph2P and Cy2P, respectively. The route was versatile and a range of electrophiles was used to prepare phosphine ligands with varying electronic and steric properties. These electrophiles (of the R2PCl variety) were often specifically prepared from PCl3 and the corresponding Grignard reagent. Phosphine ligands synthesised in this research project using our DoM (directed ortho metallation) methodology were tested in Suzuki cross-coupling reactions of deactivated aryl bromides and some aryl chlorides and showed excellent reactivity, with the advantage that the ligands of this study are oxidatively and hydrolytically stable. Efforts were also made to modifying the phosphinic amide-functionalised phosphine ligands to generate their water-soluble derivatives. One way of achieving this was by the hydrolysis of the phosphinic amide moiety to the phosphinic acid analogue. Salts of these phosphinic acid derivatives have promising activities as water-soluble substrates. This route was successful only iii with less electron-rich systems providing an opening for more research in this regard. In an alternative synthetic route to polar water-soluble phosphines it was envisioned that phosphonate-derivatised phosphines would offer access to water-soluble phosphine ligands by using milder hydrolysis conditions. These phosphonate systems were also tested for DoM reactivity and showed promising reactivity. Phosphonates have not previously being employed as DoM groups, and this alone expands the application and potential scope of P-based DoM groups. / Prof. D.B.G. Williams