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89
NafionÒ was developed by DuPont chemists in the 1960s7 via
copolymerization of tetrafluoroethylene (Teflon monomer) with perfluorinated
vinyl ethers terminated with sulfonated groups. NafionÒ resins belong to a class of
polymers with ionic properties referred to as “ionomers”. NafionÒ resins have
certain desirable properties such as inertness to chemical attack and permselectivity
which allows preferentially cation diffusion to occur faster than anion diffusion
across a membrane. These properties make NafionÒ resins extensively useful for
various commercial applications such as membranes in chlor-alkali cells for
chlorine production, in fuel cells, batteries, ion-exchange resins and so on. The use
of the acidic form of NafionÒ (Figure 3.1) was serendipitous and once discovered
was extensively used in a wide variety of organic transformations.8
(CF2
n
CF2)m CF CF2
CF2
CF3 CF
z
OCF2CF2 SO3H
Figure 3.1 NafionÒ-H (Polymeric Perfluorinated Resinsulfonic Acid)
Olah et al. have extensively used NafionÒ-H extensively as suitable solid
acid catalyst for a variety of organic reactions such as Friedel-Crafts alkylation9 and
acylation10 reactions, nitration,11 reductive cleavage of acetals and ketals,12 as well
as a variety of rearrangements such as pinacol-pinacolone rearrangement,13 Fries
rearrangement,14 and improved Rupe rearrangement.15 Recently, they have shown
Object Description
| Title | Synthesis of organofluorine compounds via Lewis/Bronsted acid and base catalysed reactions and related chemistry |
| Author | Vaghoo, Habiba Ebrahim |
| Author email | vaghoo@usc.edu; vaghoo@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program |
Chemistry vinyl fluorides |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2008-06-24 |
| Date submitted | 2008 |
| Restricted until | Unrestricted |
| Date published | 2008-10-31 |
| Advisor (committee member) |
Olah, George A. Shing, Katherine S. |
| Abstract | This dissertation describes the development of new and practical methodologies for the synthesis of a broad variety of fluorinated heterocycles and vinyl fluorides via acid and base catalysis, respectively. It also describes efficient cyanosilylation of carbonyl compounds using a variety of nucleophilic catalysts.; Chapter 1 explores the rich history of fluorine and its compounds. Important milestones that have made a significant contribution to the field of chemistry are highlighted with emphasis on fluorine's role in medicinal chemistry. Methods to introduce fluorine are also included in this chapter.; Chapter 2 deals with the use of gallium (III) triflate as a versatile Lewis acid for the synthesis of different fluorinated heterocycles and α-aminonitriles. The condensation-cyclization reactions of various aromatic amino derivatives with fluorinated ketones to afford the corresponding fluorinated benzimidazolines, benzothiazolines, benzoxazolines, and dihydrobenzoxazinones, as well as fluorinated 1, 5 benzodiazepines and quinoxaline derivatives is described. Also included in this chapter are the syntheses of α-aminonitriles and their fluorinated analogs via the multicomponent Strecker reaction using gallium (III) triflate. Monofluoro-, difluoro-, or trifluoromethyl groups have been incorporated into both heterocycles and the α-aminonitrile products by varying the nature of the fluorinated ketones.; In Chapter 3, Nafion^®-H, a perfluoroalkanesulfonic acid resin, is shown to be a suitable solid acid catalyst with high selectivity and catalytic activity for the one-pot synthesis of fluorinated heterocycles. The Nafion-H mediated reactions are easily achieved under mild conditions in high yields and purity. Monofluoro, difluoro and trifluoromethylated derivatives can be prepared and its advantage as a solid superacid is highlighted by the recyclability studies.; Chapter 4 describes a new approach for the stereoselective synthesis of vinyl fluorides using α-substituted fluoro(phenylsulfonyl)methane derivatives under mildly basic reaction conditions. A variety of fluorovinyl sulfones as well as α-fluoro-α,β-unsaturated carbonyls can be synthesized to afford the E-isomer.; Finally, in Chapter 5, cyanosilylation of aldehydes and ketones using various nucleophilic catalysts under mild conditions is portrayed. Use of dimethylformamide (DMF) as solvent, afforded the trimethylsilylated cyanohydrins in good to excellent yields. K2CO3 and (MeO)2P(O)(O^-)(N^+Bu4)3 have been employed as the nucleophilic catalysts for the cyanosilylation using trimethylsilyl cyanide (TMSCN). |
| Keyword | fluorine chemistry; fluorinated heterocycles; fluorinated aminonitriles; cyanosilylation |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m1729 |
| Contributing entity | University of Southern California |
| Rights | Vaghoo, Habiba Ebrahim |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-Vaghoo-2053 |
| Archival file | uscthesesreloadpub_Volume44/etd-Vaghoo-2053.pdf |
Description
| Title | Page 103 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 89 NafionÒ was developed by DuPont chemists in the 1960s7 via copolymerization of tetrafluoroethylene (Teflon monomer) with perfluorinated vinyl ethers terminated with sulfonated groups. NafionÒ resins belong to a class of polymers with ionic properties referred to as “ionomers”. NafionÒ resins have certain desirable properties such as inertness to chemical attack and permselectivity which allows preferentially cation diffusion to occur faster than anion diffusion across a membrane. These properties make NafionÒ resins extensively useful for various commercial applications such as membranes in chlor-alkali cells for chlorine production, in fuel cells, batteries, ion-exchange resins and so on. The use of the acidic form of NafionÒ (Figure 3.1) was serendipitous and once discovered was extensively used in a wide variety of organic transformations.8 (CF2 n CF2)m CF CF2 CF2 CF3 CF z OCF2CF2 SO3H Figure 3.1 NafionÒ-H (Polymeric Perfluorinated Resinsulfonic Acid) Olah et al. have extensively used NafionÒ-H extensively as suitable solid acid catalyst for a variety of organic reactions such as Friedel-Crafts alkylation9 and acylation10 reactions, nitration,11 reductive cleavage of acetals and ketals,12 as well as a variety of rearrangements such as pinacol-pinacolone rearrangement,13 Fries rearrangement,14 and improved Rupe rearrangement.15 Recently, they have shown |
