The Discovery-Oriented Approach to Organic Chemistry. 3. Boron-trifluoride Catalyzed Rearrangement of cis- and trans-Stilbene Oxides. An Exercise in 1H NMR Spectroscopy for Sophomore Organic Laboratories (original) (raw)
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Mechanisms of the Intriguing Rearrangements of Activated Organic Species
2003
Abbreviations and symbols ix Word Count xiii Chapter 1: Introduction 1 1.1 Aims of this thesis 2 1.2 A review of the mechanism of the β-acyloxyalkyl radical rearrangement 2 1.3 The β-trifluoroacetoxyalkyl radical rearrangement 14 1.4 Other isomerisations which may share the same mechanism: The rearrangement of N-alkoxy-2(1H)-pyridinethiones 16 1.5 References 19 Chapter 2: Kinetics of the β−trifluoroacetoxyalkyl radical rearrangement 23 2.1 Introduction 24 2.2 A review of β-acyloxyalkyl radical rearrangement kinetics 24 2.3 The search for a suitable system for study 31 2.3.1 2-Trifluoroacetoxy-1-hexyl radical 31 2.3.2 Reaction of β-bromoester 2.50 with Bu 3 SnH 32 2.3.3 A faster rearrangement 34 2.3.4 Reaction of β-bromoester 2.59 with Bu 3 SnH 34 2.4 Determination of the equilibrium constant 34 2.4.1 Theory 35 xv 2.4.2 Preparation of β-bromoester 2.66 36 2.4.3 Reaction of β-bromoester 2.66 with Bu 3 SnH 37 2.5 Kinetics experiments 38 2.5.1 The kinetic scheme and analytical method 38 2.5.2 Conducting the kinetic experiments and product analysis 41 2.5.3 Management of analytical complexities 43 2.5.4 Kinetics results 46 2.6 Discussion of results 53 2.7 Conclusions 57 2.8 Experimental 58 2.9 References 72 Chapter 3: A labelled-oxygen study of the regiochemistry of the β-trifluoroacetoxyalkyl radical rearrangement 74 237 5.3.7 Attempted detection and isolation of intermediates 239 5.3.7.1 Addition of a radical scavenger 239 5.3.7.2 Esr spectroscopy 240 5.3.7.3 Cyclic voltammetry 241 5.3.7.4 Isolation and attempted identification of intermediates 244 5.4 Conclusions 247 5.5 Future work 249 5.6 Experimental 250 5.7 References 277 Chapter 6: General discussion and conclusions 284 6.1 Introduction 285 6.2 The β-trifluoroacetoxyalkyl radical rearrangement 285 6.2.1 What is known about the rearrangement of the 2-methyl-2-trifluoroacetoxy-1-heptyl radical? 285 6.2.2 Migrating group electronic effects 287 6.2.3 Relationship between rearrangement regiochemistry and kinetics 288 6.2.4 Is the regiochemistry controlled by the conformation of the ester group? 289 6.2.5 Predicted dynamics for a radical ion pair intermediate