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45
2.4 Chapter 2: Experimental
General Remarks
Unless otherwise mentioned, all chemicals were purchased from
commercial sources. Gallium trifluoromethanesulfonate was prepared by the
method described below. The 1H, 13C and 19F NMR spectra were recorded on
Varian NMR spectrometers at 400 MHz. The 1H NMR chemical shifts were
determined relative to internal tetramethylsilane at d 0.0 or to the signal of a
residual protonated solvent in CDCl3. (d 7.24), 13C NMR chemical shifts were
determined relative to internal tetramethylsilane at d 0.0 or to the 13C signal of
CDCl3 at d 77.0. 19F NMR chemical shifts were determined relative to internal
CFCl3 at d 0.0. Column chromatography was carried out using Sorbent 60, 65-250
mesh silica gel. TLC was performed on plastic backed silica plates (60F254, 0.2
mm) which were visualized using UV fluorescence and Iodine.
Materials
Ga metal (99.999%) was purchased from Aldrich and
trifluoromethanesulfonic acid (99.5%) was available from 3M. Amines and
fluorinated ketones were available from different commercial sources.
2.4.1 Preparation of Ga(OTf)3
Ga(OTf)3 was prepared following the reported procedure.15 In a 100 mL
round-bottom flask, gallium metal (2.45 g, 35 mmol) was placed.
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 59 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 45 2.4 Chapter 2: Experimental General Remarks Unless otherwise mentioned, all chemicals were purchased from commercial sources. Gallium trifluoromethanesulfonate was prepared by the method described below. The 1H, 13C and 19F NMR spectra were recorded on Varian NMR spectrometers at 400 MHz. The 1H NMR chemical shifts were determined relative to internal tetramethylsilane at d 0.0 or to the signal of a residual protonated solvent in CDCl3. (d 7.24), 13C NMR chemical shifts were determined relative to internal tetramethylsilane at d 0.0 or to the 13C signal of CDCl3 at d 77.0. 19F NMR chemical shifts were determined relative to internal CFCl3 at d 0.0. Column chromatography was carried out using Sorbent 60, 65-250 mesh silica gel. TLC was performed on plastic backed silica plates (60F254, 0.2 mm) which were visualized using UV fluorescence and Iodine. Materials Ga metal (99.999%) was purchased from Aldrich and trifluoromethanesulfonic acid (99.5%) was available from 3M. Amines and fluorinated ketones were available from different commercial sources. 2.4.1 Preparation of Ga(OTf)3 Ga(OTf)3 was prepared following the reported procedure.15 In a 100 mL round-bottom flask, gallium metal (2.45 g, 35 mmol) was placed. |
