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DEVELOPMENT of NOVEL METHODOLOGIES UTILIZING QUATERNARY AMMONIUM SALTS AS CATALYSTS by LINDSEY RAE CULLEN DISSERTATION Submitted

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DEVELOPMENT OF NOVEL METHODOLOGIES UTILIZING QUATERNARY AMMONIUM SALTS AS CATALYSTS BY LINDSEY RAE CULLEN DISSERTATION Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry in the Graduate College of the University of Illinois at Urbana-Champaign, 2015 Urbana, Illinois Doctoral Committee: Professor Scott E. Denmark, Chair Professor Martin D. Burke Professor Scott K. Silverman Professor Steven C. Zimmerman ii Abstract The first half of this thesis (Chapter 2) described the development of a fluoride-promoted conjugate addition of sulfur-stabilized carbanion nucleophiles to α,β-unsaturated ketones and esters. This reaction was achieved using a substoichiometric amount of TBAF, resulting in high yields on the desired 1,4-addition product. The addition of 1,3-dithianes was given particular focus as a novel method for the preparation of differentially protect 1,4-dicarbonyl compounds. Observation by 13C NMR spectroscopy provided evidence that the reaction proceeds through an ion pair, and attempts to extend this reaction to asymmetric additions using a chiral counterion are presented in detail. The second half of this thesis (Chapter 3) details development of a phase transfer catalyzed [2,3]-sigmatropic rearrangement of allyloxy carbonyl compounds. Initial investigation focused on identifying viable substrate classes that would undergo selective [2,3]-rearrangement under phase transfer conditions. Under certain conditions, the [2,3]-sigmatropic rearrangement of allyloxy carbonyl compounds takes place in the presence of a phase transfer agent, providing a rare example of a phase transfer catalyzed unimolecular reaction. In the course of this investigation it was found that catalysis is dependent on several variables including base concentration, catalyst structure, and substrate lipophilicity. Preliminary testing of chiral, non-racemic phase transfer catalysts has shown promising levels of enantioselectivity for future development. iii Dedicated to my husband Matt iv Acknowledgements The work presented in the following pages would never have been possible without my friends, family, and mentors. Anyone who knows me, knows how much I have struggled to be happy during my time in graduate school and I truly believe it was the people who were there for me that made it possible to finish. First I would like to express by gratitude to my advisor, Scott Denmark, for his continued support and all of the doors he has opened for me in my career. I came to the group as a completely inexperienced undergraduate summer student and I am forever grateful that he gave me the opportunity to prove myself that summer. I learned more in that 10 weeks than I had up until that point, and the experience of working in such a demanding research environment solidified my choice to pursue graduate school. Of course, I also have to thank Scott for allowing me to return as a graduate student. It wasn’t easy, but now that I am near the end I can appreciate how far I have come. I am leaving Illinois as a scientist, one that not only has the “hands” to do organic chemistry, but also the critical eye to question results and design experiments. This transformation was a direct result of having such an excellent scientist as my advisor. I also have to thank Scott for his ongoing patience in being my mentor, I haven’t always made it easy. I will be forever thankful for him giving me the space I needed to succeed, the flexibility to maintain my relationship (and my sanity), and for respecting my choice in pursuing a career in polymer synthesis and avoid doing a postdoc. I could have never learned how to actually carry out experiments without the teachers I have had along the way. First, I need to thank my undergraduate advisor Matt Mio for introducing me to research, setting up an environment for me to fall in love with organic chemistry, and for helping me get to an excellent graduate program. I will never regret joining your research group and then quickly changing my major away from biology. Second, I would like to thank my first labmate, Nicola Bisek, for training me as a first year. I am sure I was a trying student at times, and it must have been difficult to share a lab with a first year at the start of your postdoc. However, you were an excellent mentor and how to do things “the right way” I learned from you. I was lucky to have a labmate I could learn so much from. I would also like to thank other senior graduate students who have helped me learn along the way. Bill Collins, thank you for volunteering to take me on as a summer student when I didn’t know anything starting out. Tyler Wilson, thank you for being my labmate for that summer and providing advice in my early years. Thank you Timothy v Chang, Nate Duncan Gould, Larry Wolf, and Dipa Kalyani for answering my questions and being excellent role models for me when I was just starting out. David Kornfilt, I will be forever thankful to have had someone else who was my same year and understood what I was going through. You were a great support and I think we learned a lot from each other. Equally (if not more) important are my friends that have always kept it interesting. Without my friends in the Denmark group I would have likely gone crazy. It is easier to work long hours if you like the people around you. I have to thank Nick Anderson for being one of my closest friends in the beginning of graduate school despite how much I was struggling. He introduced me to my husband and I will have a lifelong friend from our time overlapping in graduate school. Similarly, I have to thank Jeremy Henle for being my closest friend in the later part of my graduate school career. I am not sure I will ever have as much fun working with someone as I have with you. You have most definitely seen me at my worst and continued to be my friend anyways. Coffee time will always be a fond memory, not only for keeping me for quitting but also providing some of the best brainstorming for the PTC subgroup. I will be forever thankful that you joined PTC and weathered through the tough times when we didn’t have funding. You are an excellent chemist and an even better friend. I have to acknowledge my lunch crew/Wednesday night dinner friends, Mr. Kevin Robb, Mr. Craig Seymour, Scott “Bro” Barraza, Jeremy Henle, Olivia Lee, David Kornfilt, Carrie Levinn, and Becca Leising. Our sporadic social activities always gave me something to look forward to and I will miss how much fun I had with all of you. Lastly, I would like to thank all of the SED group past and present for their comradery and helping the time go by. Finally, I need to thank my family. My parents have made a ton of sacrifices to see that I was able to go to college and have always instilled in me a strong work ethic. I was taught to believe that anything is possible if I put my mind to it, and I think it was that attitude that was most helpful for me to succeed in graduate school. Lastly, I have to thank my husband Matt for his continued love and support through what was likely some of the most difficult times I’ve had. My ambition and enthusiasm for chemistry came at a cost to our relationship, and I am thankful that you stuck by me. I can’t believe we survived being so far apart for three years, that we planned a wedding while I was writing this thesis, and that we were able to get two jobs in the same place. You are the best thing that came out of graduate school and I can’t wait to see what is in store for us in the next 50 years. I love you. vi Table of Contents Chapter 1: Introduction to Enantioselective Quaternary Ammonium Ion Pair Catalysis ........... 1 1.1 Introduction to Enantioselective Organocatalysis .......................................................... 1 1.2 Mechanistic Principles of Ion Pair Catalysis ................................................................. 4 1.3 Enantioselective Ion Pair Catalysis ............................................................................... 8 1.4 Current Challenges in Ion Pair Catalysis ..................................................................... 12 Chapter 2: Application of Quaternary Ammonium Fluoride Salts in the Reaction of Weakly Acidic Carbon Nucleophiles ................................................................................................... 14 2.1 Introduction ................................................................................................................ 14 2.2 Background ................................................................................................................ 15 2.3 Research Objectives ................................................................................................... 22 2.4 Results ........................................................................................................................ 22 2.5 Discussion .................................................................................................................. 49 2.6 Conclusion ................................................................................................................. 57 Chapter 3: Development of a Phase Transfer Catalyzed [2,3]-Wittig Rearrangement ............ 59 3.1 Introduction ................................................................................................................ 59 3.2 Research Objectives ................................................................................................... 71 3.3 Results .......................................................................................................................
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