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The University of Chicago Advances in Pericyclic THE UNIVERSITY OF CHICAGO ADVANCES IN PERICYCLIC REACTIONS: I. NOVEL HIGHLY REACTIVE AMINODIENES FOR DIELS-ALDER REACTIONS II. DEAROMATIVE INDOLO-CLAISEN REARRANGEMENTS III. SYNTHETIC STUDIES TOWARDS HINCKDENTINE A AND MELONINE A DISSERTATION SUBMITTED TO THE FACULTY OF THE DIVISION OF THE PHYSICAL SCIENCES IN CANDIDACY FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMISTRY BY PAVEL KONSTANTINOVICH ELKIN CHICAGO, ILLINOIS JUNE 2018 To my family TABLE OF CONTENTS LIST OF SCHEMES ................................................................................................................ VII LIST OF FIGURES ..................................................................................................................... X LIST OF TABLES ................................................................................................................... XIX LIST OF ABBREVIATIONS ................................................................................................... XX ACKNOWLEDGEMENTS ................................................................................................. XXIII CHAPTER 1. INTRODUCTION. DOUBLY-ACTIVATED BUTADIENES IN THE DIELS-ALDER REACTION ....................................................................................................... 1 SECTION 1.1. ACTIVATED DIENES FOR THE DIELS-ALDER REACTION. 1,3-DISUBSTITUTED DIENES 1 SECTION 1.2. 1,1-DISUBSTITUTED DIENES AND BRASSARDS’ DIENE ............................................ 7 SECTION 1.3. CONCLUSIVE REMARKS ......................................................................................... 10 CHAPTER 2. DIELS-ALDER REACTIONS OF 1-AMINO-1-OXO-1,3-BUTADIENES: DIRECT SYNTHESIS OF 6-SUBSTITUTED AND 6,6’-DISUBSTITUTED 2- CYCLOHEXENONES ............................................................................................................... 11 SECTION 2.1. INTRODUCTION ..................................................................................................... 11 2.1.1. Use of doubly-activated dienes to access substituted cyclohexanones ....................... 11 2.1.2. Previous approaches to 6,6’-disubstituted cyclohexenones ....................................... 14 2.1.3. Previous studies on 1-dialkylamino-1-alkoxy-1,3-butadienes .................................... 19 SECTION 2.2. DEVELOPMENT OF NOVEL N-METHYL OXAZOLIDINE BUTADIENES..................... 23 2.2.1 Preparation of N - methyl oxazolidine butadiene ........................................................ 23 2.2.2 Reaction of oxazolidinebutadienes with common dienophiles ..................................... 25 iii 2.2.3. Synthesis and reactivity of substituted oxazolidinebutadienes ................................... 31 2.2.4. Synthesis and reactivity of chiral oxazolidine butadienes; attempts to access enantioenriched cyclohexenones .......................................................................................... 34 2.2.5. Hetero Diels-Alder reaction of oxazolidine butadiene ............................................... 37 2.2.6 Kinetic studies of the Diels-Alder reactions of diene 111a .......................................... 40 SECTION 2.3. CONCLUDING REMARKS ....................................................................................... 41 CHAPTER 3. MEERWEIN-ESCHENMOSER-CLAISEN REARRANGEMENT AS A ROUTE TO ASYMMETRIC 2,2 – DISUBSTITUTED INDOLES ....................................... 43 SECTION 3.1. INTRODUCTION ..................................................................................................... 43 3.1.1. 2,2 – Disubstituted Indolines In Nature ...................................................................... 43 3.1.2. Previous Synthetic Approaches To The 2,2 – Disubstituted Indoline Core Structure 46 3.1.3. Claisen rearrangement in indoles ............................................................................... 49 SECTION 3.2. DEVELOPMENT OF A GENERAL ROUTE TO ACCESS 2,2 – DISUBSTITUTED INDOLINES THROUGH CLAISEN REARRANGEMENT .................................................................... 54 3.2.1 Initial screening of different variants of the Claisen reaction ..................................... 54 3.2.2 Substrate scope of the Eschenmoser-Claisen rearrangement of indole alcohols ........ 59 3.2.3 Chirality transfer in the Eschenmoser-Claisen rearrangement as a route to access enantioenriched 2,2 – disubstituted indolines ...................................................................... 62 SECTION 3.2. CONCLUDING REMARKS ....................................................................................... 63 CHAPTER 4. TOTAL SYNTHESIS OF HINCKDENTINE A ............................................. 65 SECTION 4.1. INTRODUCTION. PREVIOUS APPROACHES TOWARDS TOTAL SYNTHESIS OF HINCKDENTINE A ...................................................................................................................... 65 SECTION 4.2. SYNTHETIC STUDIES TOWARDS HINCKDENTINE A ................................................ 72 iv 4.2.1 Proposed retrosynthesis and preliminary studies ........................................................ 72 4.2.2 Primary synthetic efforts towards total synthesis of Hinckdentine A .......................... 73 4.2.3. Alternative strategy towards Hinckdentine A – late stage amination......................... 76 4.2.3. Alternative strategies towards Hinckdentine A – late stage Pd-coupling .................. 78 4.2.4. Alternative strategies – early construction of quinazoline core. A promising avenue toward Hinckdentine A ......................................................................................................... 80 SECTION 4.3. CONCLUDING REMARKS ....................................................................................... 82 CHAPTER 5. SYNTHETIC STUDIES TOWARDS MELONINE ....................................... 84 SECTION 5.1. INTRODUCTION. .................................................................................................... 84 SECTION 5.2. SYNTHETIC STUDIES TOWARDS MELONINE. .......................................................... 85 5.2.1 Proposed retrosynthesis and preliminary studies ........................................................ 85 5.2.2 Primary attempts towards synthesis of Melonine ........................................................ 87 5.2.3 Alternative approach towards synthesis of Melonine .................................................. 91 5.2.4 Latest efforts towards the total synthesis of Melonine ................................................. 92 5.3. CONCLUDING REMARKS ...................................................................................................... 94 CHAPTER 6. EXPERIMENTAL SECTION .......................................................................... 95 6.1. General information....................................................................................................... 95 6.2. Experimental procedures and characterization data for chapter 2 ............................... 96 6.3. Experimental procedures and characterization data for chapter 3 ............................. 125 6.4. Experimental procedures and characterization data for chapter 4 ............................. 140 6.5. Experimental procedures and characterization data for chapter 5 ............................. 148 APPENDIX. ............................................................................................................................... 166 v SELECTED 1H AND 13C NMR SPECTRA ..................................................................................... 166 vi List Of Schemes Scheme 1. First heteroatom-substituted dienes for the Diels-Alder reaction ................................. 2 Scheme 2. Initial report of the Diels-Alder reaction of Danishefsky’s diene ................................ 3 Scheme 3. Enantioselective Diels-Alder reactions with Danishefskys’ diene ............................... 4 Scheme 4. 1-dialkylamino-1-siloxy-1,3-butadiene and its application in synthesis ...................... 6 Scheme 5. Other examples of 1,3-diactivated butadienes .............................................................. 6 Scheme 6. Diels-Alder reactions of 1,1-dialkoxy-1,3-butadienes .................................................. 8 Scheme 7. Use of the Brassard’s diene in the total synthesis of Epigriseofulvin .......................... 9 Scheme 8. Use of the Brassard’s diene in HDA reactions ........................................................... 10 Scheme 9. Diels-Alder reaction as a route to access substituted cyclohexanones. 1) Use of activated dienes to access 4,4-disubstituted cyclohexanones; 2) Natural products, containing 3,3 - and 2,2 -disubstituted cyclohexanones ......................................................................................... 12 Scheme 10. Utilizing 1-alkylamino-2-methoxybutadienes for the synthesis of 3,3-disubstituted cyclohexanones ............................................................................................................................. 13 Scheme 11. Identifying a doubly-activated diene to access 6,6-disubstitued cyclohexenones .... 14 Scheme 12. Accessing cyclohexenones by addition-elimination strategy ................................... 16 Scheme 13. Accessing cyclohexenones through aldol condensation ........................................... 17 Scheme 14. Accessing cyclohexenones through IBX oxidation of ketones ................................ 17 Scheme 15. Accessing cyclohexenones through the
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