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Synthetic and Mechanistic Studies on the Cross-Coupling Reactions Catalyzed by Ruthenium Complexes" (2011)

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Synthetic and Mechanistic Studies on the Cross-Coupling Reactions Catalyzed by Ruthenium Complexes Marquette University e-Publications@Marquette Dissertations (2009 -) Dissertations, Theses, and Professional Projects Synthetic and Mechanistic Studies on the Cross- Coupling Reactions Catalyzed by Ruthenium Complexes Ruili Gao Marquette University Recommended Citation Gao, Ruili, "Synthetic and Mechanistic Studies on the Cross-Coupling Reactions Catalyzed by Ruthenium Complexes" (2011). Dissertations (2009 -). Paper 105. http://epublications.marquette.edu/dissertations_mu/105 SYNTHETIC AND MECHANISTIC STUDIES ON THE CROSS-COUPLING REACTIONS CATALYZED BY RUTHENIUM COMPLEXES by Ruili Gao, B.S. A Dissertation submitted to the Faculty of the Graduate School, Marquette University, in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Milwaukee, Wisconsin May, 2011 ABSTACT SYNTHETIC AND MECHANISTIC STUDIES ON THE CROSS-COUPLING REACTIONS CATALYZED BY RUTHENIUM COMPLEXES Ruili Gao, B.A. Marquette University, 2011 Transition metal catalyzed C-H bond activation reaction is a powerful synthetic method for forming functionalized products directly from unreactive hydrocarbons, and has enormous synthetic potentials for developing chemical processes ranging from petroleum products to pharmaceutical agents. In an attempt to mimic the high stereo selectivity and region selectivity of catalytic reactions by transition metal catalysts, recent research has focused on design and synthesis of transition metal complex and the application on the coupling reactions involving C-H bond activation. Herein, we wish to report the highly effective coupling reactions involving C-H bond activation by using well-defined ruthenium catalysts. Ruthenium hydride complex was to found to have high activity and selectivity for hydrosilylation, silyl enol ethers formation and enol esters formation reactions. Throughout the course of the mechanistic investigation of the reactions, we found compelling evidence for mechanism of reactions by spectroscopic, structural techniques and computational (DFT) analysis. i ACKNOWLEDGMENTS Ruili Gao, B.A. Herein, I would like to thank the people who have contributed to this thesis. I would like to first thank my advisor, Dr. Yi for his guidance. Through these four years in the lab, you have taught me how to think and act like a chemist and to demand more from myself. I would like to thank my committee members, Dr. Donaldson, and Dr. Steinmetz, for their time, patience and suggestions. I would like to thank Dr. Timerghazin for the helps on the computational studies. I would like to thank Dr.Cai, who was always willing to share his expertise in NMR with me. Thank you for the help with the advanced NMR experiments. I would like to thank Dr. Sergey for the X-ray crystal structures of the organometallic complexes. Moreover, I would thank Chemistry Department of Marquette University for financial support. I would like to thank the Graduate School and all of the Marquette University administration. I would like to thank my friends and family for understanding and help me. I would like to dedicate this thesis to my husband. Thank you for standing behind me and fully understanding me all the time. Without you, I would not have gotten this far. ii Table of Contents ACKNOWLEDGMENTS ................................................................................................. i List of Figure .................................................................................................................... ix List of Table .................................................................................................................... xiv Chapter 1. Introduction ................................................................................................... 1 1.1 ARENE C-H BOND ACTIVATION REACTIONS ...................................................... 2 1.1.1 Photo-initiated C-H Bond Activation Reactions................................ 2 1.1.2 Non-Chelation-Assisted Arene C-H Bond Activation ....................... 4 1.1.3 Chelation-Assisted Arene C-H Bond Activation ............................... 5 1.2 C-H BOND ACTIVATION OF NITROGEN -CONTAINING COMPOUNDS ................... 8 1.2.1 C-H Bond Activation of Pyrroles ...................................................... 8 1.2.2 C-H Bond Activation of pyridine and other Nitrogen Containing Compounds ............................................................................................... 23 1.3 THE FORMATION OF SILYL ENOL ETHER INVOLVING C-H BOND ACTIVATION 30 1.4 ALKYNE C-H BOND ACTIVATION .................................................................... 34 1.4.1 The Formation of Enol Esters from the Coupling Reactions of Alkynes and Carboxylic Acids ................................................................. 34 1.4.2 The Hydrosilylation of Alkynes....................................................... 44 iii Chapter 2. Regioselective Formation of α-Vinylpyrroles from the Ruthenium-Catalyzed Cross Coupling Reaction of Pyrroles and Terminal Alkynes Involving C-H Bond Activation ..................................................................................... 57 2.1 RESULTS AND DISCUSSION ............................................................................... 57 2.2 SCOPE OF THE COUPLING REACTIONS OF PYRROLES WITH TERMINAL ALKYNES ............................................................................................................................... 59 2.2.1 Catalyst Survey ................................................................................ 59 2.2.2 Solvent Effects ................................................................................. 62 2.2.3 Reaction Scope................................................................................. 63 2.3 MECHANISM STUDIES ...................................................................................... 65 2.3.1 Hammett Study ................................................................................ 65 2.3.2 Isotope Effect Study ......................................................................... 69 2.3.3 Deuterium Labeling Studies ............................................................ 72 2.3.4 Carbon Isotope Effect Study ............................................................ 75 2.3.5 Proposed Mechanism of the Coupling Reactions of Pyrroles and Alkynes ..................................................................................................... 78 2.4 CONCLUSIONS .................................................................................................. 80 Chapter 3. Scope and Mechanistic Investigations on the Solvent-Controlled Regio- and Stereoselective Formation of Enol Esters from the Ruthenium-Catalyzed Coupling Reaction of Terminal Alkynes and Carboxylic Acids ................................. 81 iv 3.1 RESULTS AND DISCUSSION ............................................................................... 82 3.2 OPTIMIZATION STUDIES FOR THE COUPLING OF CARBOXYLIC ACID WITH TERMINAL ALKYNES ............................................................................................. 83 3.2.1 Catalyst Activity Survey .................................................................. 83 3.2.2 Solvent Effects ................................................................................. 85 3.3 REACTION SCOPE ............................................................................................. 87 3.4 MECHANISTIC STUDY ....................................................................................... 93 3.4.1 Phosphine Inhibition Study .............................................................. 93 3.4.2 Deuterium Labeling Study ............................................................... 95 3.4.3 Hammett Study ................................................................................ 97 3.4.4 Synthesis of Catalytically Relevant Ruthenium-Carboxylate........ 101 3.4.5 Synthesis of Catalytically Relevant Ruthenium–Vinylidene-Carboxylate Complexes ................................... 102 3.4.6 Kinetic Experiments on the Conversion of Complex 64 to Complex 62 and Complex 63 ................................................................................. 104 3.4.7 Derivation of the Kinetic Equation of the Conversion of 64 to 63 106 3.4.8 Proposed Mechanism ..................................................................... 109 3.5 CONCLUSIONS ................................................................................................ 112 v Chapter 4. Catalytic Formation of Silyl Enol Ethers from the Reaction of Ketones with Vinylsilanes and Their Use in Aldol-Type Condensation and Fluorination Reactions ........................................................................................................................ 113 4.1 RESULTS AND DISCUSSION ............................................................................. 114 4.2 OPTIMIZATION STUDIES FOR THE COUPLING OF KETONES WITH VINYLSILANE ............................................................................................................................. 115 4.2.1 Catalyst Activity Survey ................................................................ 115 4.3 THE SCOPE FOR THE REACTIONS OF KETONES WITH VINYLSILANE AND THE REACTION OF ENOL ETHER WITH ALDEHYDE UNDER THE TITANIUM (IV) CHLORIDE ............................................................................................................................. 117 4.3.1 The Use of Enol Silyl Ether in Fluorination Reactions and Diketone Reactions ................................................................................................
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