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135
Table 5.1 Screening of Solvents for the Cyanosilylation Reaction of 9-
anthraldehyde using K2CO3 and TMSCN.
O H
H CN
OTMS
1 mol% catalyst, 1.2 eqv TMSCN
Solvent, rt
Solvents Reaction
Time
Conversion
(%)
Yield
(%)
DMF 5 min 100 95
THF 48 h 60 -
THF+DMF
(4:1)
6 h 100 90
DCM
DCM+DMF
(4:1)
48h 47 -
48 h 10 -
Although Izumi et al.23 reported the use of some carbonates and phosphates
(but not potassium carbonate or organic phosphates) in the solid base catalyzed
cyanosilylation, our present study indicates that cyanosilylation of carbonyl
compounds in DMF is efficiently catalyzed by potassium carbonate or easily
synthesized organic phosphates such as (Bu)4N+(MeO)2P(O)O-. Ketones are
generally less reactive in cyanosilylation. Indeed we found that these reactions are
rather slow without a suitable catalyst. However, cyanosilylation of aldehydes
occurs efficiently without any catalyst, when DMF is the solvent (because DMF
itself acts as a nucleophilic activator). However, ketones also undergo reaction in
DMF without the catalyst but require longer reaction times, which can be reduced
considerably by the presence of catalysts. Use of a readily prepared metal-free
organic phosphate catalyst allows avoiding metal based initiators in reactions
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 149 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 135 Table 5.1 Screening of Solvents for the Cyanosilylation Reaction of 9- anthraldehyde using K2CO3 and TMSCN. O H H CN OTMS 1 mol% catalyst, 1.2 eqv TMSCN Solvent, rt Solvents Reaction Time Conversion (%) Yield (%) DMF 5 min 100 95 THF 48 h 60 - THF+DMF (4:1) 6 h 100 90 DCM DCM+DMF (4:1) 48h 47 - 48 h 10 - Although Izumi et al.23 reported the use of some carbonates and phosphates (but not potassium carbonate or organic phosphates) in the solid base catalyzed cyanosilylation, our present study indicates that cyanosilylation of carbonyl compounds in DMF is efficiently catalyzed by potassium carbonate or easily synthesized organic phosphates such as (Bu)4N+(MeO)2P(O)O-. Ketones are generally less reactive in cyanosilylation. Indeed we found that these reactions are rather slow without a suitable catalyst. However, cyanosilylation of aldehydes occurs efficiently without any catalyst, when DMF is the solvent (because DMF itself acts as a nucleophilic activator). However, ketones also undergo reaction in DMF without the catalyst but require longer reaction times, which can be reduced considerably by the presence of catalysts. Use of a readily prepared metal-free organic phosphate catalyst allows avoiding metal based initiators in reactions |
