Chemistry

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Browsing Chemistry by Author "Fillion, Eric"

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    Methodology Development for the Electrophilic Aromatic Amination of Secondary Amides
    (University of Waterloo, 2022-01-25) Fletcher, Randy; Fillion, Eric
    The intramolecular electrophilic aromatic amination of secondary amides was developed. Secondary N-methoxy and N-p-methoxyphenyl amides were cyclized to oxindoles by triflic anhydride mediated electrophilic activation and subsequent oxidation with a pyridine N-oxide derivative. The electrophilic nitrogen species for the N-methoxy amide was isolated and characterized. Aryl tethered 2-amidopyridine- and 2-amidopyrimidine N-oxides were additionally discovered to be synthetically valuable sources of electrophilic nitrogen under mild conditions following a simple activation protocol of triflic anhydride and tertiary amine base.
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    The Synthesis of 3-Vinylindolines by the Palladium-Catalyzed Intramolecular Allylic Alkylation of Cinnamyl Acetates and the Synthesis of Polyphenolic 4-Aryl-3,4-dihydrocoumarins by Domino Friedel-Crafts Reactions
    (University of Waterloo, 2018-10-24) Rydzik, Jordan; Fillion, Eric
    Historically, the alkylation of allylic acetates with non-stabilized C(sp3) nucleophiles has been challenging. The metal-catalyzed alkylation of allylic acetates and carbonates with organotin and organoboron reagents has significantly increased the scope of nucleophiles available to participate in such reactions; however, the generation of C(sp3)-C(sp3) bonds in this manner remains difficult. We therefore designed a substrate in order to explore the intramolecular transition metal-catalyzed alkylation of an allylic acetate with a C(sp3) organotin nucleophile. From this substrate we were able to successfully synthesize a number of 3-vinylindolines in modest to good yields in as little as seven steps through the palladium-catalyzed intramolecular allylic alkylation of cinnamyl acetates with tethered organotin nucleophiles. To the best of our knowledge this represents the first example of such a transformation, resulting in the formation of novel C(sp3)-C(sp3) bonds. It has been shown that polyphenolic procyandins, members of the flavonoid class of compounds, possess moderate affinity for a synthetic model of a proline rich region of the microtubule associated protein tau. The phosphorylation of this region of tau is thought to be correlated with the development of intraneuronal protein deposits, a hallmark of Alzheimer’s disease physiopathology. In the second part of this thesis, we set out to utilize the domino Friedel-Crafts alkylation/acylation of benzylidene Meldrum’s acids with phenols previously developed in our group for the synthesis of a number of polyphenolic 4-aryl-3,4-dihydrocoumarins, members of the neoflavonoid class of compounds. By synthesizing a library of polyphenolic neoflavonoids in this manner, which possessed variation in the number and position of hydroxyl groups about the aromatic rings, a systematic survey of the structure-activity relationship was to be conducted. This would allow us gain a better understanding of potential therapeutic agents that may be able to attenuate the formation of these intraneuronal protein deposits in the treatment of Alzheimer’s disease.
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    Synthesis, Characterization, and Reactivity of Tricarbastannatranes
    (University of Waterloo, 2016-06-16) Kavoosi, Azadeh; Fillion, Eric
    The synthesis of a series of tricarbastannatrane complexes is described, and the structure of ionic triptych complexes [N(CH2CH2CH2)3Sn](BF4), [N(CH2CH2CH2)3Sn](SbF6), [N(CH2CH2CH2)3Sn]4[(SbF6)3Cl], [(N(CH2CH2CH2)3Sn)2OH][MeB(C6F5)3] [[N(CH2CH2CH2)3Sn]2Cl0.2F0.8][B[3,5-(CF3)2C6H3]4], and [(N(CH2CH2CH2)3Sn][allyl(B(C6F5)3] is established by NMR spectroscopy and X-ray crystallography. After demonstrating the Lewis acidity of tricarbastannatrane complexes toward various Lewis bases by NMR studies, the reactivity of tricarbastannatranes in conjugate addition to electrophilic alkenes was studied. Using alkyl-tricarbastannatranes as nucleophiles, the first B(C6F5)3-promoted conjugate addition to benzylidene Meldrum’s acids was carried out under mild conditions. The mechanism of the addition has been investigated by deuterium labeling experiments. It was shown that unsaturated carbonyl compounds can be efficiently activated by the Lewis acidic tricarbastannatrane. Furthermore, the structure of the reaction intermediates was determined by NMR and mass spectroscopy. The reactivity of tricarbastannatranes was further investigated by the addition of iPr-tricarbastannatrane to activated double bonds. In the presence of catalytic amounts of B(C6F5)3, iPr-tricarbastannatrane acts as a hydride source to generate [HB(C6F5)3]–, and reduces olefins, namely benzylidene 1,3-dimethylbarbituric acids. Detailed mechanistic studies on the reduction reaction were performed by NMR spectroscopy and mass spectrometry. Conjugate additions of isopropyl group to the benzylidene 1,3-dimethylbarbituric acids along with the reduced products were observed. To expand the applications of tricarbastannatranes in carbon–carbon bond formation reactions, allyl-tricarbastannatrane was added to carbon–carbon double bonds that bear strongly electron-withdrawing substituents under mild reaction conditions. The tin enolate species, which is generated by the addition of allyl-tricarbastannatrane to benzylidene 1,3-dimethylbarbituric acid, is characterized by multinuclear NMR spectroscopy.