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Towards the Synthesis of Novel Chelates for Technetium-99M Imaging

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Towards the Synthesis of Novel Chelates for Technetium-99M Imaging Towards the Synthesis of Novel Chelates for Technetium-99m Imaging By Sheena Alexandra Hindocha A Thesis submitted in fulfilment of the requirements for the award of Doctor of Philosophy of Imperial College September 2013 Department of Chemistry, Imperial College London 1 Declaration of Originality The work reported in this thesis was completed between October 2009 and September 2013 at the Department of Chemistry, Imperial College London or GE Healthcare, Amersham. The work reported is entirely my own, unless otherwise stated through cited reference or acknowledgement and has never been previously submitted for a degree at this or any other university. Copyright Declaration The copyright of this thesis rests with the author and is made available under a Creative Commons Attribution Non-commercial No Derivatives licence. Researchers are free to copy, distribute or transmit the thesis on the condition that they attribute it, that they do not use it for commercial purposes and that they do not alter, transform or build upon it. For any reuse or redistribution, researchers must make clear to others the licence terms of this work. 2 Abstract This thesis details the synthesis of tetradentate ligand systems for use with technetium-99m with a focus on sulphur donors. The synthesis of a series of S4 tetradentate ligands is detailed (Chapter 3). The ligands with general formula Me2PS(CH2)2S(CH2)nS(CH2)2PSMe2 where n = 2 – 4 (3.1 – 3.3). The ligands were reacted with technetium-99m, [ReO2(py)4]Cl and [ReOCl3(PPh3)2] unfortunately evidence for complexation was not obtained. In order to gain an understanding of the coordination chemistry of the ligands 3.1 – 3.3 were successfully complexed to Cu(I), Ag(I) and Pd(II) centres, the compounds and structures are discussed in chapter 3. The synthesis of ligands containing 1-methyl-2H-imidazole-2-thione units, which act as S donors is featured in chapter 4. Challenges met during the synthesis of the S4 and N2S2 ligands are discussed. P2S2 (4.12 and 4.16) ligands were synthesised by the reaction of the imidazole unit with 1,3-propanebis(phenyldihydroxymethylphosphine) dichloride. This led to the subsequent synthesis of an analogous P2O2 (4.17) ligand using 1-ethyl-2H-imidazolin-2-one. The P2S2 and P2O2 chelates were reacted with PdCl2 to produce Palladium(II) complexes. Reactions with [ReOCl3(PPh3)2] were also completed and although pure samples were not + isolated, there is evidence that [ReO2L] complexes were synthesised. The synthesis of a tetradentate phosphine oxime (P2N2) ligand system is the focus of chapter 5. The synthetic challenges encountered during the proposed synthesis are detailed along with alternative synthetic routes. The synthesis of analogous P2N2 compounds is also reported. Whilst evidence for the target chelate (5.2) was obtained its synthesis could not be fully confirmed. 3 Table of Contents Declaration………………………………………………………………….. 2 Abstract……………………………………………………………………... 3 Acknowledgements…………………………………………………………. 8 Abbreviations……………………………………………………………….. 9 1.0 Introduction………………………………………………………......... 13 1.1 Technetium……………………………………………………………. 14 1.2 Chemistry of Rhenium and Technetium………………………............. 16 1.2.1 Binary Compounds………………………………………………….. 17 1.2.2 Oxidation States……………………………………………………... 18 1.3 Technetium Complexes……………………………………………….. 20 1.3.1 With Bidentate Ligands……………………………………………… 20 1.3.2 With Tridentate Ligands…………………………………………….. 22 1.3.3 With Tetradentate Ligands………………………………………....... 24 1.3.4 Organometallic Complexes………………………………………...... 29 1.4 Technetium-99m as an Imaging Agent………………………………... 33 1.4.1 Production of Technetium-99m……………………………………... 34 1.4.2 Imaging Technetium-99m………………………………………........ 35 1.4.3 Kit Formulations…………………………………………………….. 36 1.5 The Place of Technetium-99m in Nuclear Imaging………………….... 39 1.6 References……………………………………………………………... 41 2.0 Thesis Justification and Rationale…………………………………..... 45 2.1 Challenges and Opportunities in 99mTc Chemistry…………………..... 46 2.2 Project Aims and Objectives………………………………………….. 46 2.3 Relevant Literature……………………………………………………. 50 2.3.1 Thioether Bridged Systems with Tc(V) and Re(V)…………………. 50 4 2.3.2 Phosphine Bridged Systems with Tc(V) and Re(V)………………… 51 2.4 Thesis Synopsis……………………………………………………….. 53 2.5 References……………………………………………………………. 54 3.0 Synthesis and Characterisation of Tetradentate Ligands Incorporating the Thiophosphoryl Donors…………………………………………... 56 3.1 Chapter Aims and Overview………………………………………...... 57 3.2 Introduction…………………………………………………………… 58 3.3 Ligand Synthesis…………………………………………………….... 61 3.4 Reaction with Technetium-99m and Rhenium………………………... 65 3.4.1 Rhenium Complexes………………………………………….. 66 3.4.2 Technetium-99m Complexes………………………………….. 73 3.5 Metal Complexes…………………………………………………….... 78 3.5.1 Copper(I) Complexes………………………………………….. 78 3.5.2 Silver(I) Complexes………………………………………….... 89 3.5.3 Palladium(II) Complexes…………………………………….... 92 3.5.4 Comparison of X-ray Crystal Structures……………………… 97 3.5.5 Can the Rhenium and Technetium-99m results be explained?... 104 3.6 Conclusion…………………………………………………………….. 109 3.7 Experimental………………………………………………………….. 109 3.7.1 Synthesis of Starting Materials………………………………... 109 3.7.2 General Synthesis of 3.1 – 3.3………………………………… 111 3.7.3 General Reaction Conditions for the Synthesis of Re(V) Complexes................................................................................... 113 3.7.4 General Reaction Conditions for the Synthesis of 99mTc Complexes…………………………………………………….. 113 3.7.5 General Synthesis of 3.6 – 3.8………………………………… 114 3.7.6 General Synthesis of 3.9 – 3.11……………………………….. 115 3.7.7 General Synthesis of 3.12 3.13……………………………..…. 117 3.8 References………………………………………………………….......118 4.0 Towards the Synthesis of Tetradentate Ligands Containing the Mercaptoimidazole Moiety……………………………………………121 4.1 Chapter Aims and Overview…………………………………………. 122 5 4.2 Introduction…………………………………………………………... 124 4.3 Synthesis of Compound 4.Y………………………………………….. 128 4.3.1 Attempted Synthesis of 4.Y…………………………………… 128 4.3.2 Synthesis of 1-hydroxymethyl-2-methylimidazole-2-thione….. 135 4.3.3 Synthesis of 1-chloromethyl-3-methylimidazole-2-thione hydrochloride………………………………………………….. 138 4.4 Reactions Towards the Synthesis of 4.9 and 4.10…………………….. 141 4.4.1 Attempted Synthesis of 4.9……………………………………. 142 4.4.2 Attempted Synthesis of 4.10…………………………………... 145 4.5 Synthesis of 4.12 and Analogous Ligands……………………………..147 4.5.1 Synthesis of 1,3- bis(phenylbishydroxymethylphosphonium)propane dichloride..148 4.5.2 Synthesis of Bisphosphine Bisimidazole Tetradentate Ligand Systems………………………………………………………... 150 4.5.3 Complexation of 4.12, 4.16 and 4.17 with Palladium(II)……... 156 4.5.4 Complexation of 4.12, 4.16 and 4.17 with Rhenium(V)……… 158 4.6 Conclusion……………………………………………………………..161 4.7 Experimental…………………………………………………………...163 4.7.1 Synthesis of Starting Materials………………………………...164 4.7.2 Attempted Synthesis of 4.2 – 4.6……………………………... 165 4.7.3 Synthesis of 4.7 – 4.9…………………………………………. 166 4.7.4 Synthesis of 4.11 – 4.18………………………………………. 169 4.7.5 General Synthesis of 4.19 – 4.21…………………………....... 172 4.7.6 General Synthesis of 4.22 – 4.24……………………………... 173 4.7.7 General Synthesis of 4.25 – 4.27…………………………....... 175 4.8 References……………………………………………………………..176 5.0 Synthesis of a Tetradentate Phosphine Oxime Ligand System……..178 5.1 Chapter Aims and Overview…………………………………………. 179 5.2 Introduction…………………………………………………………... 180 5.3 Investigation of Proposed Ligand System…………………………….. 182 5.3.1 Reactions of 1,3-bis(phenylphosphino)propane with chloro-butane compounds……………………………………………………. 185 6 5.3.2 Reaction of 1,3-bis(phenylphosphino)propane and 2-bromo-2- methylbutane…………………………………………………....187 5.4 Attempted Synthesis of Tetradentate Phosphine Oxime Ligands……...191 5.4.1 Reaction of 1-chloro-2-propanone oxime and 1,3- bis(phenylphosphino)propane………………………………….192 5.4.2 Reaction of 5.8 and 1,3-bis(phenylphosphino)propane……….195 5.5 Towards the Synthesis of 5.2…………………………………………. 198 5.5.1 Proposed Synthesis of 5.2 ……………………………………. 198 5.5.2 Attempted Oxidation of 5.2…………………………………....205 5.6 Conclusion……………………………………………………………. 206 5.7 Experimental………………………………………………………….. 208 5.7.1 General Synthesis of Phosphine Compounds…………………. 208 5.7.2 Synthesis of Nitroso Compounds……………………………... 211 5.8 References…………………………………………………………….. 212 6.0 Conclusions and Future Work………………………………………. 214 6.1 The synthesis of a ligand system containing the thiophosphoryl moiety…………………………………………………………………. 215 6.2 The synthesis of tetradentate ligands containing the mercaptoimidazole unit……………………………………………………………………..218 6.3 Attempted synthesis of a tetradentate phosphine oxime ligand………. 221 6.4 References…………………………………………………………….. 224 7.0 Appendices……………………………………………………………...225 7.1 X-ray Crystal data for 3.2…………………………………………………….226 7.2 X-ray Crystal data for 3.6…………………………………………………….228 7.3 X-ray Crystal data for 3.8…………………………………………………….230 7.4 X-ray Crystal data for 3.12…………………………………………………...232 7.5 X-ray Crystal data for 3.13…………………………………………………...234 7.6 X-ray Crystal data for 4.11…………………………...………………………237 7 Acknowledgments Nick, I don’t know how to thank you for your support and encouragement over the past four years. I didn’t think I’d make it and had it not been for you I wouldn’t have. I know it’s not much of a repayment but if you ever need a babysitter let me know. The ever changing faces of the Long group have been a constant source of friendship and entertainment. From the come dine with me group to the mid-week drinks crew I will not
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