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FSU ETD Template Florida State University Libraries Electronic Theses, Treatises and Dissertations The Graduate School 2018 Radical Reactions to Form Expanded Polyaromatics: Electronic and Steric Control Audrey Marie Hughes Follow this and additional works at the DigiNole: FSU's Digital Repository. For more information, please contact [email protected] FLORIDA STATE UNIVERSITY COLLEGE OF ARTS AND SCIENCES RADICAL REACTIONS TO FORM EXPANDED POLYAROMATICS: ELECTRONIC AND STERIC CONTROL By AUDREY MARIE HUGHES A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2018 Audrey Marie Hughes defended this dissertation on November 7, 2018. The members of the supervisory committee were: Igor V. Alabugin Professor Directing Dissertation Bruce R. Locke University Representative Kenneth Hanson Committee Member Wei Yang Committee Member The Graduate School has verified and approved the above-named committee members and certifies that the dissertation has been approved in accordance with university requirements. ii TABLE OF CONTENTS List of Tables ...................................................................................................................................v List of Figures ................................................................................................................................ vi List of Schemes ............................................................................................................................ viii Abstract .......................................................................................................................................... xi 1. EXO-DIG RADICAL CASCADES OF SKIPPED ENEDIYNES: BUILDING A NAPHTHALENE MOIETY WITHIN A POLYCYCLIC FRAMEWORK ..............................1 1.1 Introduction ..........................................................................................................................1 1.2 Results and Discussion ........................................................................................................2 1.2.1 Substrate Design .......................................................................................................2 1.2.2 Cascade Transformation............................................................................................3 1.3 Conclusion ...........................................................................................................................7 2. TRACELESS DIRECTING GROUPS IN RADICAL CASCADES: FROM OLIGOALKYNES TO FUSED HELICENES WITHOUT TETHERED INITIATORS ..........8 2.1 Introduction ..........................................................................................................................8 2.2 Results and Discussion ......................................................................................................11 2.2.1 Chemoselectivity in Radical Cascades ...................................................................14 2.2.2 Barriers for the Cyclization of Vinyl Radicals ........................................................17 2.2.3 Full Radical Cascade and Return of the Radical at the β-Carbon ...........................18 2.2.4 Functionalization of Stannyl Benzofluorenes .........................................................20 2.2.5 Formation of Larger Polyaromatic Systems ...........................................................21 2.2.6 Selected Photophysical Properties of Benzo[a]fluorene Chromophores ................22 2.3 Conclusion .........................................................................................................................23 3. RADICAL ALKYNE PERI-ANNULATION REACTIONS FOR THE SYNTHESIS OF FUNCTIONALIZED PHENALENES, BENZANTHRENES, AND OLYMPICENE ............24 3.1 Introduction ........................................................................................................................24 3.2 Results and Discussion ......................................................................................................27 3.2.1 Computational Analysis ..........................................................................................29 3.3 Conclusion .........................................................................................................................33 4. ELECTRONIC AND STERIC CONTROL OF RADICAL PERI-CYCLIZATIONS ON ROUTE TO EXPANDED POLYAROMATICS ......................................................................34 4.1 Introduction ........................................................................................................................34 4.2 Results and Discussion ......................................................................................................36 4.2.1 Substituent Effects: Direct Substitution at the Alkyne ..........................................37 iii 4.2.2 Indirect Substituent Effects: Presence and Orientation of a Methoxy Group at the Propargylic Carbon .................................................................................................38 4.2.3 Effect of the Aromatic Target .................................................................................40 4.2.4 The Role of Aromaticity .........................................................................................44 4.2.5 Stereoelectronic Effects in Peri-cyclizations ..........................................................46 4.2.6 Analysis of the 5-membered Cycle Formation .......................................................48 4.2.7 Comparison of Alkyne and Peri-cyclizations .........................................................49 4.3 Conclusion .........................................................................................................................50 APPENDICES ...............................................................................................................................52 A. CHAPTER ONE SUPPORTING INFORMATION .................................................................52 B. CHAPTER TWO SUPPORTING INFORMATION ................................................................73 C. CHAPTER THREE SUPPORTING INFORMATION ..........................................................102 D. CHAPTER FOUR SUPPORTING INFORMATION ............................................................141 References ....................................................................................................................................179 Biographical Sketch .....................................................................................................................189 iv LIST OF TABLES Table 1. Scope of substrates for radical cascades. ..........................................................................4 Table 2. 1-(2-Alkynylphenyl)propargyl methyl ethers. ................................................................12 Table 3. Radical cascade of propargyl methyl ethers. ...................................................................13 Table 4. Natural Bond Orbital (NBO) analysis of 28b, 28b-t, 48b, and 48b-t and their corresponding starting materials. Second order perturbation energies for the orbital interactions are given in kcal/mol . ....................................................................................................................48 Table 5. Crystal data and structure refinement for 3b...................................................................68 Table 6. Atomic coordinates and equivalent isotropic displacement parameters (Å2) for 3b. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor....................................69 Table 7. Screening against different reagents, initiators, and solvents. ........................................70 Table 8. Full scope of substrates for radical cascades...................................................................71 Table 9. Full scope of 1-(2-alkynylphenyl)propargyl methyl ethers. ...........................................94 Table 10. Optimization of reaction conditions. .............................................................................95 Table 11. Further optimization of SnBu3 addition to alkyne 1a. ..................................................95 Table 12. Full scope of radical cascade of propargyl methyl ethers. ............................................96 Table 13. Photophysical properties of select complexes in CH2Cl2. ..........................................100 Table 14. Optimization of the Sn‐promoted radical cyclization of alkyne 6a.a ..........................140 v LIST OF FIGURES Figure 1. Skipped diynes are readily available. ..............................................................................2 Figure 2. Regioselectivity of radical attack agrees with the radical addition to the terminal aromatic system in the final cyclization step. ..................................................................................6 Figure 3. Geometries and energies of the four diastereomeric fused helicenes 20b (only one of the two enantiomers is shown for each structure, ΔG and energies in kcal/mol at 110°C). ..........22 Figure 4. a. Possible patterns and strategies for cycloaddition annulations at an aromatic system; b. cyclization annulations; c. evolution of polyaromatic ribbon synthesis; d. benzannulative approaches to growth of carbon nanostructures. ............................................................................25 Figure 5. Graphene edge types and sites of reactivity with a peri-radical
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