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Ligand Transfer Reactions of Hypervalent Iodine Reagents with Phosphorus Compounds

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Ligand Transfer Reactions of Hypervalent Iodine Reagents with Phosphorus Compounds Ligand Transfer Reactions of Hypervalent Iodine Reagents with Phosphorus Compounds by JASMIN ELJO A thesis presented to the University of Waterloo in fulfillment of the thesis requirements for the degree of Master of Science in Chemistry Waterloo, Ontario, Canada, 2018 © Jasmin Eljo 2018 Author’s Declaration I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii Abstract Many hypervalent iodine compounds are used as versatile reagents in synthetic organic chemistry. Hypervalent iodine reagents are capable of oxidizing trivalent phosphorus compounds into pentavalent, by transferring their heteroatom ligands onto phosphorus. These pentavalent phosphorus compounds can have a different reactivity profile than either the hypervalent iodine(III) reagents or the parent phosphorus(III) compounds. As such, in addition to their applications in organic reactions, they are utilized in fields such as medicinal chemistry, biochemistry, and chemical biology. The goal of this project is to synthesize pentavalent phosphorus species from trivalent phosphorus compounds using relatively cheap, environmentally benign, hypervalent iodine reagents. Chapter 1 describes the attempted synthesis of dihalo- and diacyloxytriphenyl- phosphoranes. In this study we successfully synthesized and isolated Ph3PF2 through the reaction 31 of TolIF2 and Ph3P. This reaction was monitored using P NMR spectroscopy which revealed clean conversion of Ph3P to Ph3PF2, which was relatively fast in chloroform. In the similar way, we treated Ph3P with hypervalent iodine reagents (diacetoxyiodo)benzene, bis(trifluoroacetoxyiodo)benzene and a chlorinated cyclic iodane. Even though the expected phosphoranes have not been observed, we found that the Ph3P/hypervalent iodine reagent system can be utilized for functionalization of alcohols. When a set of primary, secondary and tertiary alcohols were treated with Ph3P/hypervalent iodine reagent system, the conversion of primary alcohols to the corresponding fluoride, acetate, trifluoroacetate or chloride, respectively, were feasible. The reactivity of secondary and tertiary alcohols varied depending on the Ph3P/hypervalent iodine reagent system. iii Chapter 2 describes the halogenation of secondary phosphine oxides and subsequent reaction with various nucleophiles. We found that the presence of electron donating substituents on the aromatic ring gave better results on fluorination compared with the parent diphenylphosphine oxide. Chlorination of secondary phosphine oxides in the presence of a nucleophile like ethanol led to the formation of phosphinates with excellent yields. iv Acknowledgements I would like to thank my supervisor Dr. Graham Murphy for giving me an opportunity to pursue my master’s degree under his guidance. It is with immense gratitude that I acknowledge all the support, guidance, and the patience, he offered me for the past two years. I would like to thank my advisory committee, Dr. Michael Chong and Dr. Eric Fillion for all their support. I would like to extend my gratitude to Dr. Rick Marta, Dr. Laura Ingram and Julie Goll whom with I had the opportunity to work as a teaching assistant. It was a great learning experience. I would like to thank Jan Venne for all her support with NMR. There are no words to express my gratitude to my fellow colleagues in the Murphy lab. I always considered myself lucky to be part of such a wonderful group. I owe my deepest gratitude to Richard Tran for everything he has done for me from day one itself. Even after his graduation, he spent time to edit my thesis. I am indebted to Jason Tao not only for answering my questions, but, also finding time to edit my thesis even though he was busy with his thesis submission. I take this opportunity to thank Dr. Zhensheng Zhao for sharing the fumehood and for all the fun time we had together. I also take this opportunity to thank Myriam St. Onge Carle for her help with NMR studies and Dr. Leanne Racicot for her help with GCMS. I am thankful to Tristan Chidley for paying attention to all my doubts. I would like to express my gratitude to Liam Britt and also to former members Dr. Kaivalya Kulkarni and Abhinandan Shyamsundar. I would like to thank my cousin Athulya for all her help with auto formatting word. Last, but not the least I would like to thank my husband Eljo and our kids Adish and Eva for their love, encouragement, and support for the entire period. v To Eljo, Adish and Eva vi Table of Contents Author’s Declaration ..................................................................................................................................... ii Abstract ........................................................................................................................................................ iii Acknowledgements ....................................................................................................................................... v Dedication .................................................................................................................................................... vi List of Figures ............................................................................................................................................... ix List of Schemes.............................................................................................................................................. x List of Tables ............................................................................................................................................... xii List of Abbreviations ...................................................................................................................................xiii Chapter 1: Hypervalent Iodine Reagents and Triphenylphosphine .............................................................. 1 1.1 Introduction to Hypervalent Iodine Compounds ................................................................................ 1 1.1.1 Structure and Bonding ................................................................................................................. 1 1.1.2 Examples of HVI Reagents............................................................................................................ 3 1.1.3 Reactivity of λ3-Iodanes ............................................................................................................... 4 1.2 Introduction to Organophosphorus Compounds ............................................................................... 9 1.2.1 Phosphorus(III) Compounds ....................................................................................................... 12 1.2.1.1 Triphenylphosphine (Ph3P) ................................................................................................. 12 1.2.2 Dihalotriphenylphosphoranes (Ph3PX2) ..................................................................................... 14 1.2.2.1 Diiodotriphenylphosphorane (Ph3PI2) ................................................................................. 16 1.2.2.2 Dibromotriphenylphosphorane (Ph3PBr2) .......................................................................... 17 1.2.2.3 Dichlorotriphenylphosphorane (Ph3PCl2)............................................................................ 17 1.2.2.4 Difluorotriphenylphosphorane (Ph3PF2) ............................................................................. 19 1.3 Reactions of Ph3P and Hypervalent Iodine Reagents........................................................................ 21 1.4 Functionalization of Alcohols ............................................................................................................ 25 1.5 Proposal ............................................................................................................................................ 26 1.6 Synthesis of Difluorotriphenylphosphorane and Alkyl Fluorides ..................................................... 27 1.7 Synthesis of Trifluoroacetates .......................................................................................................... 38 1.8 Synthesis of Acetates ........................................................................................................................ 40 1.9 Functionalization of Alcohols Using Cyclic Chloro(benzoyloxy)iodane ............................................. 43 1.10 General Mechanism for the Functionalization of Alcohols via Phosphoranes. .............................. 45 1.11 Conclusion ....................................................................................................................................... 47 1.12 Experimental Procedures for Chapter 1 ......................................................................................... 47 vii 1.12.1 General Experimental Details .................................................................................................. 47 1.12.2 Synthesis of p-(Difluoroiodo)toluene (8) ................................................................................. 48 1.12.3 Synthesis of (Dichloroiodo)benzene (15) ................................................................................. 49 1.12.4 Synthesis of Difluorotriphenylphosphorane ............................................................................ 49 1.12.5 General
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