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New Chiral Auxiliaries for the [3+2]-Cycloaddition of Nonstabilised Azomethine Ylides

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New Chiral Auxiliaries For The [3+2]-Cycloaddition Of Nonstabilised Azomethine Ylides Allan Rostrup Forup Jensen A thesis submitted in partial fulfilment of the degree of Doctor of Philosophy Christopher Ingold Laboratories University College London London 20 Gordon Street WC1H OAJ ProQuest Number: 10610918 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 10610918 Published by ProQuest LLC(2017). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 /\cjmowieugemenis First and foremost I wish to thank my supervisor, Professor K. J. Hale, for the constant support, encouragement and guidance he has provided throughout the duration of this project. I also wish to take this opportunity to thank my sponsor, Rhone- Poulenc-Rorer, without whom this project would not have been possible. I also wish to thank past and present members of the Hale group for their friendship and encouragement. In particular, Dr. J. Cai was an invaluable help and inspiration. For their friendship and enormous support through good and bad times, Rukpong Tupprasoot, Neha Jogiya, Andrew Calabrese, Dr. Gurpreet Bhatia, Marc Hummersone, Rafaqat Hussain, also deserve to be mentioned. Thanks also to some of my other friends in the department, in particular James Madden, Darren Greening, and Letitia So for making the whole experience much more enjoyable. I also wish to thank the technical staff at the Christopher Ingold Laboratories for their services including Jill Maxwell (NMR, analytical analysis), Alan Stones (analytical analysis) and Steve Corker (low-resolution mass spectra). Thanks also to the technical staff at ULIRS Mass Spectrometry Service Centre at the London School of Pharmacy, in particular Mike Cocksedge, who performed high-resolution mass spectra. Finally, I owe a great debt of gratitude to my parents and family for their love and support for the duration of the project. 2 /\Dsiraci The [3+2]-cycloaddition reaction of nonstabilised azomethine ylides to alkenes is a valuable synthetic method for the assembly of functionalised pyrrolidines. However, there are only a few examples of such cycloadditions being successfully performed with an unstabilised azomethine ylide that has been tethered to a removable chiral auxiliary. Most of the reactions studied so far have exhibited only modest levels of diastereoselectivity (ca. 60 % d.e.), and in every case, destruction of the chiral auxiliary has proven necessary before the newly fashioned chiral pyrrolidine cycloadduct could be liberated. In the first part of this thesis, the potential utility of optically pure 1,1- dialkylhydrazines as chiral auxiliaries for nonstabilised azomethine ylide cycloadditions to alkenes has been investigated. While the preparation of several chiral 1,1- dialkylhydrazines was carried out successfully, the formation of the N-amino azomethine ylide precursors from these hydrazines failed, occasionally giving interesting unwanted and unexpected by-products. The second part of this thesis focuses on the evaluation of several new chiral auxiliaries as stereochemical control elements for 1,3-dipolar cycloadditions of azomethine ylides to alkenes. This work failed with some auxiliaries and was partially successful with others. The successful [3+2]-cycloaddition reactions were all performed with dimethyl fumarate as the dipolarophile, but afforded little or no stereoselectivity. The cleavage of the newly-created pyrrolidine systems from these auxiliaries under various conditions also proved to be unsuccessful. During this work a new method for the preparation of 1,1-dialkylhydrazines by the reduction of iV-nitroso precursors was discovered. The potential utility of this method has been evaluated, and the results are discussed in Chapter 4. 3 moments Acknowledgements ........................................................................................................ 2 Abstract ........................................................................................................................... 3 Abbreviations ................................................................................................................. 8 Chapter 1 A general survey of azomethine ylide [3+2]-cycloaddition reactions in organic chemistry ................................................................................................... 10 1.0 Introduction ............................................................................................... 10 1.1 Historical aspects of azomethine ylide chemistry ................................... 13 1.2 The generation of azomethine ylides with achiral alkenes and alkynes.................................................................................................. 14 1.2.1 The aziridine route to azomethine ylides ................................ 14 1.2.2 The desilylation route to azomethine ylides ........................... 17 1.2.3 The tautomerisation route to azomethine ylides ..................... 33 1.2.4 The deprotonation route to azomethine ylides ....................... 34 1.2.5 The decarboxylation route to azomethine ylides ................... 40 1.2.6 The iV-oxide route to azomethine ylides ................................. 42 1.2.7 The A-metaUation route to azomethine ylides ........................ 44 1.2.8 General summary of the methods for the generation of azomethine ylides for cycloaddition reactions .......................... 47 1.3 Asymmetric induction in the reactions of azomethine ylides with alkenes ............................................................................................... 48 1.4 Natural products via the [3+2]-cycloaddition reactions of azomethine ylides ....................................................................................... 88 1.5 Closing rem arks ........................................................................................ 94 4 Evaluation of a new chiral auxiliary for nitrogen in the asymmetric [3+2]-cycloaddition of nonstabilised azomethine ylides .................................... 96 2.0 Introduction ............................................................................................. 96 2.1 Initial preparation of cycloaddition precursor 2 .................................. 98 2.2 Alternative preparation towards the cycloaddition precursor 2 .......... 101 2.2.1 Preparation of hydrazine 1 ...................................................... 101 2.2.2 Attempted preparation of the hydrazine cycloaddition precursor 2 ............................................................................... 119 2.3 Remarks................................................................................................... 128 Chapter 3 An attempt at introducing new chiral auxiliaries for the [3+2]-cycloaddition reactions of nonstabilised azomethine ylides ...................................................... 129 3.1 Investigations into the use of a mannose based auxiliary for the [3+2]-cycloadditions of azomethine ylides ........................................... 129 3.2 An attempt at the use of D-glucose as a chiral auxiliary for azomethine ylide [3+2]-cycloadditions .................................................. 135 3.3 Evaluation of a novel camphor-derived auxiliary in the [3+2]-cycloaddition reaction of nonstabilised azomethine ylides 137 3.3.1 [(lR)]-en<7o-(+)-3-Bromocamphor as starting material 137 3.3.2 The utilisation of a camphor amine 7 6 ................................. 138 3.3.3 Attempted removal of the pyrrolidine moiety ...................... 142 3.3.4 Attempted introduction of a phenyl group into the auxiliary 143 3.4 Attempting the preparation of a double [3+2]-cycloaddition precursor based on (1 S,2R)-(-)- 1,2-diamino-1,2-diphenylethane 152 3.4.1 Preparation of (1 S, 2S')-(-)-l,2-diamino- 1,2-diphenylethane 1 1 1 ............................................................................................ 152 3.4.2 Attempted preparation of the cycloaddition precursors 111/120.................................................................................... 155 3.5 Investigation into the [3+2]-cycloaddition precursor using methyl a-D-glucopyranoside as the starting material ...................................... 159 5 3.5.2 Cycloaddition of azomethine ylide precursor 133 ................ 163 3.5.3 Attempted removal of the pyrrolidine section from the cycloadduct 134ab .................................................................. 163 3.5.4 Remarks................................................................................... 166 3.6 Utilising methyl (3-D-fructopyranoside as the chiral auxiliary for azomethine ylide [3+2]-cycloaddition reactions .................................. 167 3.6.1 The preparation of the amine 1 4 8 .......................................... 168 3.6.2 The preparation of the cycloaddition precursor 150 ............. 168 3.6.3 Cycloaddition of 150 ............................................................... 169 3.6.4 The attempted removal of the pyrrolidine system from the sugar moiety ............................................................................
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