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Exploration of the Nazarov Cyclization Reaction by Mariam Zaky

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Exploration of the Nazarov Cyclization Reaction by Mariam Zaky Exploration of the Nazarov Cyclization Reaction by Mariam Zaky Submitted in partial fulfillment of the requirements for the degree of Master of Science Dalhousie University Halifax, NS March 2016 ! Copyright by Mariam Zaky, 2016 ! ! ! ! Table of Contents List of Tables ................................................................................................................ iv List of Figures ................................................................................................................ v List of Schemes ............................................................................................................. vi Abstract ......................................................................................................................... ix List of Abbreviations and Symbols Used ...................................................................... x Acknowledgements .................................................................................................... xiii Chapter 1 - Introduction ................................................................................................. 1 1.1 The Classical Nazarov Reaction .................................................................... 1 1.1.2 Conformational Preference Influenced by "-Substituents ..................... 2 1.1.3 Polarized Nazarov reaction .................................................................... 2 1.2 The Interrupted Nazarov Reaction ................................................................. 3 1.2.1 Nazarov Reactions of Allenyl Vinyl Ketones ............................................... 5 1.2.2 Interrupted Nazarov Reactions of Allenyl Vinyl Ketones ............................. 7 1.3 Nazarov Reaction of Aromatic Substrates ................................................... 12 1.4 Thesis Chapters ............................................................................................ 14 Chapter 2 - Synthesis and Nazarov Cyclization of Allenyl Aryl Ketones ................... 16 2.1 Introduction .................................................................................................. 16 2.2 Results and Discussion ................................................................................ 17 2.2.1 Synthesis .............................................................................................. 17 2.2.2 Nazarov Reactions ...................................................................................... 18 2.2.3 Interrupted Nazarov reaction ...................................................................... 25 2.2.4 Computational Work ................................................................................ 27 2.3 Conclusions and Future Work ..................................................................... 29 ! ""! 2.4 Experimental Section ................................................................................... 30 2.4.1 General Information ................................................................................. 30 2.4.2 Synthesis and Characterization ................................................................ 31 Chapter 3 - Attempted Synthesis of a Tethered Allenyl Vinyl Ketone ....................... 59 3.1 Introduction .................................................................................................. 59 3.2 Results and Discussion ................................................................................ 60 3.2.1 Synthesis .................................................................................................. 60 3.3 Conclusions .................................................................................................. 65 3.4 Experimental Section ................................................................................... 66 3.4.1 Synthesis and Characterization ................................................................ 66 Chapter 4 - Trapping of Allenyl Vinyl Ketone by Allyltrimethylsilane ...................... 76 4.1 Introduction .................................................................................................. 76 4.2 Results and Discussion ................................................................................ 77 4.2.1 Synthesis .................................................................................................. 77 4.3 Conclusions ........................................................................................................ 79 4.4.1 Synthesis and Characterization ................................................................ 80 Chapter 5 – Conclusion ................................................................................................ 83 References .................................................................................................................... 85 Appendix A – NMR spectra for Chapter 2 .................................................................. 88 Appendix B – NMR spectra for Chapter 3 ................................................................ 135 Appendix C – NMR spectra for Chapter 4 ................................................................ 149 ! ! ! """! List of Tables ! Table 1. Nazarov reactions of allenyl aryl ketones ...................................................... 20! Table 2. Nazarov reaction of AAKs catalyzed by In(OTf)3 ........................................ 24! ! "#! List of Figures ! Figure 1.1 Three conformers of "-substituted divinyl ketone ....................................... 2! Figure 1.2 The s-trans/s-trans conformation of an AVK and a divinyl ketone ............. 7! Figure 2.1 Five substrates from the computational study ............................................ 27! Figure 2.2 Computed (#B97X-D/6-31G) transition state geometries for the BF3- mediated cyclizations of A, B, C, D, and E ......................................................... 29! Figure 4.1 Steric interactions in the s-trans/s-trans conformation of divinyl ketone with $-substituents ............................................................................................... 76! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! #! List of Schemes ! Scheme 1.1 Acid-catalyzed Nazarov reaction of a divinyl ketone ................................ 1! Scheme 1.2 Conrotatory and disrotatory ring closure ................................................... 2! Scheme 1.3 Polarized Nazarov cyclization .................................................................... 3! Scheme 1.4 The interrupted Nazarov reaction ............................................................... 3! Scheme 1.5 Intramolecular trapping of the oxyallyl cation generated from a trienone substrate ................................................................................................................. 4! Scheme 1.6 Oxyallyl cation interception using allyltrimethylsilane ............................. 5! Scheme 1.7 Electrocyclization and tandem (4 + 3) cycloaddition of divinyl ketone .... 5! Scheme 1.8 Synthesis of a cross-conjugated cyclopentenone from the Nazarov reaction of allene ether ........................................................................................... 6! Scheme 1.9 Nazarov cyclization of an AVK on silica gel ............................................. 7! Scheme 1.10 Resonance contributors of the oxyallyl cation formed from an allenyl vinyl ketone ............................................................................................................ 8! Scheme 1.11 Synthesis of a 5-hydroxycyclopent-2-enone by an interrupted Nazarov reaction ................................................................................................................... 9! Scheme 1.12 Halogenated cyclopentenones synthesized by interrupted Nazarov reactions ................................................................................................................. 9! Scheme 1.13 Nazarov cyclization and tandem (4 + 3) cycloaddition .......................... 10! Scheme 1.14 Nazarov cyclization and tandem (3 + 2) cycloaddition .......................... 10! Scheme 1.15 Nazarov cyclization and tandem (4 + 3) cycloaddition using an oxygen- substituted diene ................................................................................................... 11! Scheme 1.16 Trapping at positions a and c using a bulky carbon nucleophile ........... 11! Scheme 1.17 Trapping of an oxyallyl cation using tosyl-substituted pyrrole .............. 12! Scheme 1.18 Nazarov reaction of aryl vinyl ketone .................................................... 13! ! #"! Scheme 1.19 Nazarov reaction of aryl vinyl ketone to give an indanone .................... 13! Scheme 1.20 Nazarov reaction of oxazolidinone-substituted aryl vinyl ketone .......... 14! Scheme 1.21 Polarized Nazarov reaction of aromatic vinyl ketone ............................ 14! Scheme 2.1 5-endo-dig Cyclizations of allenyl aryl ketone reported by Nagao ......... 17! Scheme 2.2 Preparation of allenyl aryl ketones ........................................................... 18! Scheme 2.3 Grignard reaction with 4-methoxybenzaldehyde ..................................... 18! Scheme 2.4 Isomerization of Nazarov products .......................................................... 19! Scheme 2.5 Stabilizing effect of electron-donating group on oxyallyl cation of AAK .............................................................................................................................. 21! Scheme 2.6 Two regioisomers obtained from the Nazarov
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