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The Synthesis of Highly Substituted Aromatics and the Reaction of Alkene Pi Systems with Vinyl Cations

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The Synthesis of Highly Substituted Aromatics and the Reaction of Alkene Pi Systems with Vinyl Cations University of Vermont ScholarWorks @ UVM Graduate College Dissertations and Theses Dissertations and Theses 2018 The yS nthesis of Highly Substituted Aromatics and the Reaction of Alkene Pi Systems with Vinyl Cations Nicholas Jarrod Dodge University of Vermont Follow this and additional works at: https://scholarworks.uvm.edu/graddis Part of the Organic Chemistry Commons Recommended Citation Dodge, Nicholas Jarrod, "The yS nthesis of Highly Substituted Aromatics and the Reaction of Alkene Pi Systems with Vinyl Cations" (2018). Graduate College Dissertations and Theses. 936. https://scholarworks.uvm.edu/graddis/936 This Dissertation is brought to you for free and open access by the Dissertations and Theses at ScholarWorks @ UVM. It has been accepted for inclusion in Graduate College Dissertations and Theses by an authorized administrator of ScholarWorks @ UVM. For more information, please contact [email protected]. THE SYNTHESIS OF HIGHLY SUBSTITUTED AROMATICS AND THE REACTION OF ALKENE PI SYSTEMS WITH VINYL CATIONS A Dissertation Presented by Nicholas Dodge to The Faculty of the Graduate College of The University of Vermont In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Specializing in Chemistry October, 2018 Defense Date: July 16, 2018 Dissertation Examination Committee: Matthias Brewer, Ph.D., Advisor Adam C. Whalley, Ph.D., Advisor Victor May, Ph.D., Chairperson José S. Madalengoitia, Ph.D. Willem R. Leenstra, Ph.D. Cynthia J. Forehand, Ph.D., Dean of the Graduate College ABSTRACT This dissertation presents work on three distinct projects that are all related to unique pi systems: Aldol cyclotrimerizations have been used to achieve the rational chemical synthesis of fullerenes, fullerene fragments, and carbon nanotubes in the past. Under certain conditions this reaction produces the corresponding cyclotetramer which has sometimes been regarded as an undesired byproduct. This work details efforts to synthesize and use these cyclotetramers toward a synthesis of a C240 fullerene fragment. One principal focus in this work is tridecacyclene, a cyclic tetramer of acenaphthylene given its name by our group for its thirteen rings. Relatively low yields for the synthesis of tridecacyclene and its derivatives drove us to investigate the mechanism of its formation and attempt to optimize its production. During this process, novel dione products were isolated from the attempted cyclotetramerization of two dimeric species. Characterization of these products by X-ray crystallography gave valuable insight into the reaction pathway, leading us to a new proposed mechanism of formation for the cyclotetramerization products observed in these aldol reactions. β-Hydroxy-α-diazoketones are suitable progenitors to vinyl cation intermediates whose use in chemical synthesis is relatively unexplored. As part of an extensive project to develop the chemistry of vinyl cations for use in carbon-carbon bond forming reactions to build important molecular scaffolds, a range of β-hydroxy-α-diazoketones containing a pendent nucleophilic alkene were synthesized. Treatment of these compounds with a Lewis acid gave either lactone or cyclopentenone products depending on the substrate used. Proposed herein is a mechanism involving a key acylium intermediate which, depending on the position of the pendent alkene, results in different product outcomes. In a collaborative effort to further investigate the known anti-cancer properties of fusarochromanone, a fungal metabolite that is isolated from Fusarium-infected feed from cold climates, a large-scale synthesis of this natural product was explored. An efficient, scalable synthesis of the previously prohibitively expensive amidochromanone starting material has been achieved and its elaboration to fusarochromanone has been demonstrated. ACKNOWLEDGEMENTS I am grateful to many people who helped me along the way during graduate school and other times in my life. First, thanks to my advisors, Dr. Adam Whalley and Dr. Matthias Brewer, for teaching me how to do and think about science… and so much more. Thanks also to the wonderful group mates and friends who worked with me—Rob, Dan, Jonathan, Adam, Sarah, Ramya, Jian, and all the rest—there are too many to list here. The Chemistry Department staff has also been wonderfully accommodating, thanks especially to Andrea, Kevin, Bruce, Monika, and Angie. I am also indebted to Sandy Wurthmann at UVM and Natalie Machamer and Barbara Cole at the University of Maine—you all helped me hone my teaching skills and confidence and ultimately gave me the boost and support that I needed to seek my own independent career. My family also has my eternal gratitude. My siblings, Katie, A.J. and Jake, are truly the greatest gifts my parents ever have given me. I would not trade their love and comradery for anything. To my Dad, words could never do justice to thank you properly for the support you showed me during the formative years of my life. Finally, to the love of my life, Dongmin—many days I felt sorry for putting you through the struggle of dealing with me during the emotional roller coaster ride that I was going through outside of graduate school but crossing the finish line with you smiling at my side made it all worth it. Finally, I would like to thank The Lady, whose memory I pledge to keep alive. ii TABLE OF CONTENTS ACKNOWLEDGEMENTS ............................................................................................. ii LIST OF TABLES ........................................................................................................... vi LIST OF FIGURES AND SCHEMES .......................................................................... vii CHAPTER 1: SYNTHESIS OF CONTORTED AROMATICS: BACKGROUND .. 1 1.1 Introduction to Contorted Aromatics ...................................................................... 1 1.2 The Chemical Synthesis of Buckybowls ................................................................ 6 1.2.1 Corannulene and Introduction to [n]Circulenes ................................................ 7 1.2.2 Hemibuckminsterfullerene and Sumanene ...................................................... 12 1.2.3 Circumtrindene ................................................................................................ 15 1.2.4 Other Buckybowls and Palladium-Catalyzed Arylation .................................. 18 1.3 Tetrabenzo[8]circulene and the Scholl Reaction .................................................. 20 1.4 Cyclotetramers from Aldol Cyclotrimerizations of Aromatic Ketones ................ 24 CHAPTER 2: THE CYCLOTETRAMERIZATION OF ACENAPHTHENONES AND SYNTHETIC EFFORTS TOWARD CONTORTED AROMATICS .............. 29 2.1 Progress toward a C240 Fullerene Fragment .......................................................... 29 2.1.1 Synthesis of Tridecacyclene ............................................................................ 29 2.1.2 Attempted Scholl Reactions of Tridecacyclene ............................................... 31 2.1.3 Synthesis of Chlorinated Tridecacyclene and Initial Arylation Attempts ....... 32 2.2 Exploring the Cyclotetramerization Pathways of Acenaphthenones.................... 36 2.2.1 Background and Motivation ............................................................................ 36 2.2.2 Efforts to Selectively Form Cyclotetramers .................................................... 39 2.2.3 Isolation and Characterization of Novel Diones .............................................. 41 iii 2.2.4 Proposed Mechanism of Dione Formation ...................................................... 43 2.2.5 Final Attempts at Forming the Buckybowl and Conclusions .......................... 49 2.3 Asymmetric Tetrabenzo[8]circulene .................................................................... 53 2.3.1 Synthetic Approach ......................................................................................... 53 2.3.2 Synthesis of “Masked Diyne” Dienophile ....................................................... 55 2.3.3 Synthesis of Thiophene Oxide Dienes ............................................................. 57 2.3.4 Key Diels-Alder Reaction and Photochemical Decarbonylation Attempts ..... 59 2.4 Synthetic Effort Toward Extended TB[8]C Derivatives ...................................... 61 2.5 Conclusions and Future Work .............................................................................. 64 CHAPTER 3: THE REACTION OF VINYL CATIONS WITH PENDENT ALKENES ....................................................................................................................... 66 3.1 Background and Motivation ................................................................................. 66 3.2 Initial Investigations ............................................................................................. 74 3.2.1 Preparation of Requisite β-Hydroxy-α-diazoketone ........................................ 74 3.2.2 Screening and Optimizing Conditions for Vinyl Cation Capture by Alkene .. 76 3.3 Reaction Scope ..................................................................................................... 79 3.4 Proposed Mechanisms and Explanations for Vinyl Cation Capture Outcomes ... 83 3.5 Conclusions and Future Work .............................................................................. 93 CHAPTER 4: SYNTHESIS OF FUSAROCHROMANONE ..................................... 94 4.1 Background and Motivation ................................................................................
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