15 Preparation of fluorinated olefins and acetylenes
-
Axel Haupt
Abstract
Unsaturated fluorinated compounds have a certain importance, especially as monomeric building blocks for the preparation of polymeric functional materials. Apart from that, they are important synthetic intermediates, as they are typically susceptible to a variety of further derivatizations [3275]. Finally, they may introduce interesting structural properties to molecules, rendering them suitable for applications. Due to this, a number of efficient synthetic methods has been developed and reviewed over the last decades [2899, 3275-3279]. In addition, a comprehensive summary of preparative strategies toward di-, tri- and tetrasubstituted monofluoroalkenes has been published some years ago [3280]. In general, synthetic approaches toward fluoroolefins and -acetylenes are comparable to standard hydrocarbon chemistry, where the most important preparative methods are certainly based on elimination reactions. Fluorine substituents may also be directly introduced to vinylic positions, when a leaving group is replaced by nucleophilic or electrophilic fluorinating reagents. Furthermore, a few coupling procedures play a role, which are somehow also comparable to the synthesis of nonfluorinated molecules, especially in terms of Wittig- or Horner-Wadsworth-Emmons reactions, but also for Pd-catalyzed cross-coupling of fluorovinyl-fragments. In the same way, C-F-bonds of fluorinated olefins may be selectively activated by transition metal catalysts, and subsequently coupled to a variety of other carbon fragments [3234]. However, the focus in the following section will be on the transfer of fluorine substituents to unsaturated carbon-centers and the formation of unsaturated C-C-bonds with fluorinated alkylidene species. Thus, transition metal mediated coupling-reactions of complete, fluorinated vinyl-units will not be included herein. In contrast to hydrocarbon chemistry, transition-metal catalyzed metathesis techniques only play a minor role in organofluorine chemistry. Nevertheless, a number of substrates with a fluorinated backbone or side-chain may be used in this type of transformation, which has been reviewed some time ago [3281]. The selective transition-metal catalyzed hydrodefluorination of highly fluorinated olefins can also be a valuable tool for the preparation of partly fluorinated molecules and will therefore also be briefly discussed in this chapter.
Abstract
Unsaturated fluorinated compounds have a certain importance, especially as monomeric building blocks for the preparation of polymeric functional materials. Apart from that, they are important synthetic intermediates, as they are typically susceptible to a variety of further derivatizations [3275]. Finally, they may introduce interesting structural properties to molecules, rendering them suitable for applications. Due to this, a number of efficient synthetic methods has been developed and reviewed over the last decades [2899, 3275-3279]. In addition, a comprehensive summary of preparative strategies toward di-, tri- and tetrasubstituted monofluoroalkenes has been published some years ago [3280]. In general, synthetic approaches toward fluoroolefins and -acetylenes are comparable to standard hydrocarbon chemistry, where the most important preparative methods are certainly based on elimination reactions. Fluorine substituents may also be directly introduced to vinylic positions, when a leaving group is replaced by nucleophilic or electrophilic fluorinating reagents. Furthermore, a few coupling procedures play a role, which are somehow also comparable to the synthesis of nonfluorinated molecules, especially in terms of Wittig- or Horner-Wadsworth-Emmons reactions, but also for Pd-catalyzed cross-coupling of fluorovinyl-fragments. In the same way, C-F-bonds of fluorinated olefins may be selectively activated by transition metal catalysts, and subsequently coupled to a variety of other carbon fragments [3234]. However, the focus in the following section will be on the transfer of fluorine substituents to unsaturated carbon-centers and the formation of unsaturated C-C-bonds with fluorinated alkylidene species. Thus, transition metal mediated coupling-reactions of complete, fluorinated vinyl-units will not be included herein. In contrast to hydrocarbon chemistry, transition-metal catalyzed metathesis techniques only play a minor role in organofluorine chemistry. Nevertheless, a number of substrates with a fluorinated backbone or side-chain may be used in this type of transformation, which has been reviewed some time ago [3281]. The selective transition-metal catalyzed hydrodefluorination of highly fluorinated olefins can also be a valuable tool for the preparation of partly fluorinated molecules and will therefore also be briefly discussed in this chapter.
Kapitel in diesem Buch
- Frontmatter I
- Preface V
- Foreword VII
- Contents IX
-
Part A: Introduction to fluorine chemistry
- Introduction to fluorine chemistry 1
- 1 Sources of fluorine in nature 5
- 2 Elemental fluorine 9
- 3 Hydrogen fluoride 15
- 4 Preparation of fluorinated compounds [35] 23
- 5 Common solid-state structures of inorganic fluorides [35] 31
- 6 Properties of fluorinated compounds 35
- 7 Health and environmental aspects of fluorinated compounds 37
- 8 19F-NMR – an important analytical tool for fluorine chemists [53, 54] 43
-
Part B: Inorganic fluorine chemistry
- Inorganic fluorine chemistry 53
- 9 Main group element fluorides 55
- 10 Transition metal fluorides and rare earth metal fluorides 161
-
Part C: Organic fluorine chemistry
- Organic fluorine chemistry 281
- 11 Fluoroorganic compounds – unusual properties and versatile applications 283
- 12 General reaction types and reagents for the introduction of fluorine 301
- 13 Fluorination of aliphatic substrates 319
- 14 Fluorination of (hetero-) aromatic compounds 415
- 15 Preparation of fluorinated olefins and acetylenes 453
- 16 Solutions to study questions 479
- Bibliography 537
- Index 617
Kapitel in diesem Buch
- Frontmatter I
- Preface V
- Foreword VII
- Contents IX
-
Part A: Introduction to fluorine chemistry
- Introduction to fluorine chemistry 1
- 1 Sources of fluorine in nature 5
- 2 Elemental fluorine 9
- 3 Hydrogen fluoride 15
- 4 Preparation of fluorinated compounds [35] 23
- 5 Common solid-state structures of inorganic fluorides [35] 31
- 6 Properties of fluorinated compounds 35
- 7 Health and environmental aspects of fluorinated compounds 37
- 8 19F-NMR – an important analytical tool for fluorine chemists [53, 54] 43
-
Part B: Inorganic fluorine chemistry
- Inorganic fluorine chemistry 53
- 9 Main group element fluorides 55
- 10 Transition metal fluorides and rare earth metal fluorides 161
-
Part C: Organic fluorine chemistry
- Organic fluorine chemistry 281
- 11 Fluoroorganic compounds – unusual properties and versatile applications 283
- 12 General reaction types and reagents for the introduction of fluorine 301
- 13 Fluorination of aliphatic substrates 319
- 14 Fluorination of (hetero-) aromatic compounds 415
- 15 Preparation of fluorinated olefins and acetylenes 453
- 16 Solutions to study questions 479
- Bibliography 537
- Index 617
