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20
As will be discussed in this chapter, gallium (III) triflate has been
extensively used for various condensation-cyclization reactions to afford the
corresponding heterocycles such as benzimidazolines, benzothiazolines,
benzoxazolines, dihydrobenzoxazinones, quinoxalines and 1, 5 benzodiazepines. It
has also proved to be a superior catalyst for the Strecker reaction. It provides a
general route for the synthesis of mono, di and trifluoromethylated amino acids via
the formation of the corresponding aminonitrile intermediates.
2.2 Chapter 2: Results and Discussion
2.2.1 Efficient One-Pot Synthesis of Fluorinated Benzimidazolines,
Benzothiazolines, Benzoxazolines, and Dihydrobenzoxazinones.
Benzimidazolines, benzothiazolines, benzoxazolines and
dihydrobenzoxazinones are important classes of heteroaromatics.
Benzimidazolines, often called as organic hydrides, can act as good reducing agents
and good hydrogen storage materials in many organic reactions.16,17,18,19
Benzothiazolines and benzoxazolines are used as plant growth regulants,
herbicides, anticonvulsants, in photochromic dyes and for the treatment of ADD
(Attention Defficiency Disorder).20,21 Dihydrobenzoxazinones are used in
analgesics and also as useful building blocks for drugs and pharmaceuticals, which
possess antiviral, antifungal, antibacterial and antiparasitic properties.22,23
Benzimidazolines 3 are generally synthesized from the reaction of 1,2-
phenylenediamines 1a and benzaldehyde (Scheme 2.1).24,25,26,27
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 34 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 20 As will be discussed in this chapter, gallium (III) triflate has been extensively used for various condensation-cyclization reactions to afford the corresponding heterocycles such as benzimidazolines, benzothiazolines, benzoxazolines, dihydrobenzoxazinones, quinoxalines and 1, 5 benzodiazepines. It has also proved to be a superior catalyst for the Strecker reaction. It provides a general route for the synthesis of mono, di and trifluoromethylated amino acids via the formation of the corresponding aminonitrile intermediates. 2.2 Chapter 2: Results and Discussion 2.2.1 Efficient One-Pot Synthesis of Fluorinated Benzimidazolines, Benzothiazolines, Benzoxazolines, and Dihydrobenzoxazinones. Benzimidazolines, benzothiazolines, benzoxazolines and dihydrobenzoxazinones are important classes of heteroaromatics. Benzimidazolines, often called as organic hydrides, can act as good reducing agents and good hydrogen storage materials in many organic reactions.16,17,18,19 Benzothiazolines and benzoxazolines are used as plant growth regulants, herbicides, anticonvulsants, in photochromic dyes and for the treatment of ADD (Attention Defficiency Disorder).20,21 Dihydrobenzoxazinones are used in analgesics and also as useful building blocks for drugs and pharmaceuticals, which possess antiviral, antifungal, antibacterial and antiparasitic properties.22,23 Benzimidazolines 3 are generally synthesized from the reaction of 1,2- phenylenediamines 1a and benzaldehyde (Scheme 2.1).24,25,26,27 |
