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Non-metal catalyzed cyclization of α-alkynyl hydrazines to form azaproline derivatives: a mechanism study
Title
Non-metal catalyzed cyclization of α-alkynyl hydrazines to form azaproline derivatives: a mechanism study.
Creator
Nagy, Edith, Maity, Pradip, Lepore, Salvatore D.
Date Issued
2012-04-06
PURL
http://purl.flvc.org/fcla/dt/3349037
Subject Headings
Synthetic organic chemistry, Alkynes, Non-metal catalyzed cyclization, Derivatization --proline, Pyrazolines -- Derivatives, Biochemical models, Hydrazines
Format
Document (PDF)
Exploring cation-π interactions in a sophomore Organic Chemistry Laboratory experiment
Title
Exploring cation-π interactions in a sophomore Organic Chemistry Laboratory experiment.
Creator
Horowitz, Andrew, Rucco, Dominic, St. Germain, Elijah, Lepore, Salvatore D., Rezler, Evonne
Abstract/Description
An Organic Chemistry Lab experiment is being developed and adapted from work recently published by Maity and Lepore [1] investigating the cyclization of substituted β-alkynyl hydrazines to yield azaproline derivatives. The mechanism of this reaction is putatively driven by cation-π interaction of alkynyl hydrazine with a tetrabutylammonium ion. This experiment will present students with a cutting-edge research concept to explore the role of tetrabutylammonium in the cyclization of substituted...
Show moreAn Organic Chemistry Lab experiment is being developed and adapted from work recently published by Maity and Lepore [1] investigating the cyclization of substituted β-alkynyl hydrazines to yield azaproline derivatives. The mechanism of this reaction is putatively driven by cation-π interaction of alkynyl hydrazine with a tetrabutylammonium ion. This experiment will present students with a cutting-edge research concept to explore the role of tetrabutylammonium in the cyclization of substituted β-alkynyl hydrazines. Reaction kinetics will be probed by thin-layer chromatography and azaproline derivative product(s) will be characterized by IR spectroscopy. Ultimately, our goal is to implement a modern research-based, cost-effective, and safe bioorganic experiment into Florida Atlantic University’s undergraduate Organic Chemistry Laboratory curriculum.
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Date Issued
2014
PURL
http://purl.flvc.org/fau/fd/FA0005024
Subject Headings
College students --Research --United States.
Format
Document (PDF)
Scalable Synthesis of 18-Crown-6 Based Lariat Ethers and Their Evaluation as Catalysts in Ester Hydolyosis
Title
Scalable Synthesis of 18-Crown-6 Based Lariat Ethers and Their Evaluation as Catalysts in Ester Hydolyosis.
Creator
Suresh, Vallabh, Jana, Susovan, Lepore, Salvatore D., Charles E. Schmidt College of Science
Abstract/Description
The syntheses of various Lariat crown ethers including several not previously reported and their efficient purification are presented. The synthesis route brings together reactions from a variety of previous works leading to a robust and generalized approach to these C-pivot lariats. The main steps are condensation of functionalized diols with penta-ethylene glycol ditosylate in the presence of potassium as a templating cation. Purification of the final products was achieved without...
Show moreThe syntheses of various Lariat crown ethers including several not previously reported and their efficient purification are presented. The synthesis route brings together reactions from a variety of previous works leading to a robust and generalized approach to these C-pivot lariats. The main steps are condensation of functionalized diols with penta-ethylene glycol ditosylate in the presence of potassium as a templating cation. Purification of the final products was achieved without chromatography by forming crown ether complexes with potassium nitrate followed by their precipitation. The catalytic activity of these lariat ethers in the hydrolysis of carboxylic esters was explored.
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Date Issued
2015
PURL
http://purl.flvc.org/fau/fd/FA00005213
Subject Headings
College students --Research --United States.
Format
Document (PDF)
synthesis and reactivity of nucleophile assisting leaving groups
Title
The synthesis and reactivity of nucleophile assisting leaving groups.
Creator
Cohn, Pamela., Florida Atlantic University, Lepore, Salvatore D.
Abstract/Description
The synthesis and reactivity of Nucleophile Assisting Leaving Groups was studied in order to assess the rate enhancement of nucleophilic substitution reactions. Various Nucleophile Assisting leaving groups were synthesized, all of them containing a coordinating arm positioned ortho to an electrophilic center on a benzene ring. The various coordinating arms had novel geometries and binding properties. Their reactivity was studied with a variety of metal salts and the kinetics of the reactions...
Show moreThe synthesis and reactivity of Nucleophile Assisting Leaving Groups was studied in order to assess the rate enhancement of nucleophilic substitution reactions. Various Nucleophile Assisting leaving groups were synthesized, all of them containing a coordinating arm positioned ortho to an electrophilic center on a benzene ring. The various coordinating arms had novel geometries and binding properties. Their reactivity was studied with a variety of metal salts and the kinetics of the reactions was studied with 1H-NMR spectroscopy. This method provided a quantitative measurement of the rate enhancement observed in the substitution reactions from the rate constants obtained. In the case of certain crown ether-containing substrates, NMR experiments suggest that the mechanism of substitution proceeds in two steps, the first being a pre-coordination of the metal salt with the coordinating arm, followed by a conversion of the complex to products.
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Date Issued
2006
PURL
http://purl.flvc.org/fcla/dt/13375
Subject Headings
Chemical reaction, Conditions and laws of, Organic reaction mechanisms, Intermediates (Chemistry), Organotransition metal compounds
Format
Document (PDF)
Synthesis of allenyl carbonyls and their use as heterodienes in a novel inverse electron demand hetero-Diels-Alder reaction
Title
Synthesis of allenyl carbonyls and their use as heterodienes in a novel inverse electron demand hetero-Diels-Alder reaction.
Creator
Bromfield, Deborah Christina Deirdre., Florida Atlantic University, Lepore, Salvatore D.
Abstract/Description
We report the development of a novel hetero-Diels-Alder reaction involving the use of allenyl carbonyls as heterodienes. We have described the synthesis of a variety of allenyl carbonyls via a base promoted and manganese mediated isomerization of alkynyl carbonyls for use in methodology studies. In our model studies, a variety of enamines were utilized effectively as dienophiles to form "hydrolyzed" Diels-Alder adducts while investigating optimal reaction conditions. Initial studies towards...
Show moreWe report the development of a novel hetero-Diels-Alder reaction involving the use of allenyl carbonyls as heterodienes. We have described the synthesis of a variety of allenyl carbonyls via a base promoted and manganese mediated isomerization of alkynyl carbonyls for use in methodology studies. In our model studies, a variety of enamines were utilized effectively as dienophiles to form "hydrolyzed" Diels-Alder adducts while investigating optimal reaction conditions. Initial studies towards the synthesis of an allenyl ester tethered to an aldehyde for an eventual application in an intramolecular Diels-Alder reaction were performed. Possible mechanisms were proposed while computational studies were performed in attempt to rationalize product selectivity.
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Date Issued
2005
PURL
http://purl.flvc.org/fcla/dt/13222
Subject Headings
Diels-Alder reaction, Ring formation (Chemistry), Heterocyclic compounds, Organic compounds--Synthesis, Carbonyl compounds--Synthesis, Alkenes, Organic nitro chemistry
Format
Document (PDF)
Cell-surface glycan-lectin interactions for biomedical applications
Title
Cell-surface glycan-lectin interactions for biomedical applications.
Creator
Rodriguez Benavente, Maria Carolina, Lepore, Salvatore D., Cudic, Predrag, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
Carbohydrate recognition is one of the most sophisticated recognition processes in biological systems, mediating many important aspects of cell-cell recognition, such as inflammation, cell differentiation, and metastasis. Consequently, lectin-glycan interactions have been intensively studied in order to mimic their actions for potential bioanalytical and biomedical applications. Galectins, a class of ß-galactoside-specific animal lectins, have been strongly implicated in inflammation and...
Show moreCarbohydrate recognition is one of the most sophisticated recognition processes in biological systems, mediating many important aspects of cell-cell recognition, such as inflammation, cell differentiation, and metastasis. Consequently, lectin-glycan interactions have been intensively studied in order to mimic their actions for potential bioanalytical and biomedical applications. Galectins, a class of ß-galactoside-specific animal lectins, have been strongly implicated in inflammation and cancer. Galectin-3 is involved in carbohydrate-mediated metastatic cell heterotypic and homotypic adhesion via interaction with Thomsen-Friedenreich (TF) antigen on cancer-associated MUC1. However, the precise mechanism by which galectin-3 recognizes TF antigen is poorly understood. Our thermodynamic studies have shown that the presentation of the carbohydrate ligand by MUC1-based peptide scaffolds can have a major impact on recognition, and may facilitate the design of more potent and specific galectin-3 inhibitors that can be used as novel chemical tools in dissecting the precise role of galectin-3 in cancer and inflammatory diseases. Another lectin, odorranalectin (OL), has been recently identified from Odorrana grahami skin secretions as the smallest cyclic peptide lectin, has a particular selectivity for L-fucose and very low toxicity and immunogenicity, rendering OL an excellent candidate for drug delivery to targeted sites, such as: (1) tumor-associated fucosylated antigens implicated in the pathogenesis of several cancers, for overcoming the nonspecificity of most anticancer agents; (2) the olfactory epithelium of nasal mucosa for enhanced delivery of peptide-based drugs to the brain.
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Date Issued
2015
PURL
http://purl.flvc.org/fau/fd/FA00004405
Subject Headings
Biopharmaceutics, Carbohydrates -- Therapeutic use, Cell differentiation, Drug delivery systems, Glycoproteins, Glycoslation, Mice as laboratory animals, Peptides -- Derivatives, Pharmaceutical biotechnology
Format
Document (PDF)
Catalytic Asymmetric Isomerizations of Alkynes To Allenes And Their Diastereoselective Functionalization Facilitated By An Organomanganese Auxiliary
Title
Catalytic Asymmetric Isomerizations of Alkynes To Allenes And Their Diastereoselective Functionalization Facilitated By An Organomanganese Auxiliary.
Creator
Roy, Animesh, Lepore, Salvatore D., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
The present dissertation research is largely focused on the methods to synthesize highly substituted allene derivatives from alkynes in conjugation with carbonyl-containing functional groups. A key aspect of this research involves methylcyclopentadienylmanganese dicarbonyl (MMD), an inexpensive and air-stable organometallic auxiliary linked to alkynyl carbonyls via an η2-bond. This auxiliary influences bond formation to achieve enhanced stereoselectivity without itself undergoing any chemical...
Show moreThe present dissertation research is largely focused on the methods to synthesize highly substituted allene derivatives from alkynes in conjugation with carbonyl-containing functional groups. A key aspect of this research involves methylcyclopentadienylmanganese dicarbonyl (MMD), an inexpensive and air-stable organometallic auxiliary linked to alkynyl carbonyls via an η2-bond. This auxiliary influences bond formation to achieve enhanced stereoselectivity without itself undergoing any chemical transformation. Chapter 1 accounts various examples of such transition metal auxiliaries including MMD. Typically conjugated alkynyl carbonyls do not isomerize to thermodynamically less favored allenes. However, with the MMD auxiliary in place, alkynyl carbonyl compounds undergo facile 1,3-proton shifts in the presence of a mild base to produce allene isomers. Although allenyl aldehydes are important building blocks, we note that direct methods to prepare them nonracemically are not known. Chapter 2 describes the development of a new cinchonine-based phase transfer catalyst to access non-racemic allenyl aldehydes from MMD-complexed alkynyl aldehydes. With the manganese auxiliary in place, nonracemic allenyl aldehydes were obtained in a weakly basic biphasic reaction system via enantioselective protonation conditions. Chapter 3 describes the second use of the MMD auxiliary to direct nucleophilic addition reactions to allenyl aldehydes for the preparation of 2,3-allenols diastereoselectively. In the absence of the MMD auxiliary, nucleophilic reactions to the carbonyl group of axially chiral allenyl aldehydes is poorly diastereoselective, which is a long-standing problem. We observed that, in addition to leading to non-racemic allenyl aldehydes, the MMD auxiliary could also be used to improve diastereoselectivity in carbonyl additions due to its proximal position on the 2,3-bond of the allenyl aldehyde. Chapter 4 describes the use of allenyl esters as metathesis quenching agents. It was observed that the addition of an allenyl ester after a metathesis reaction was complete; facilitate the removal of most ruthenium metal impurities using simple silica chromatographic purification.
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Date Issued
2017
PURL
http://purl.flvc.org/fau/fd/FA00004918
Subject Headings
Transition metal catalysts., Stereochemistry., Chemistry, Organic., Chemistry, Physical and theoretical., Asymmetric synthesis.
Format
Document (PDF)
Development of Crown Ether Nucleophilic Catalysts (CENCs) and their Application in Rapid Fluorination of Silicon for PET Imaging & Diversification Reactions of γ-Silyl Allenyl Esters to All-carbon Quaternary Stereogenic Centers
Title
Development of Crown Ether Nucleophilic Catalysts (CENCs) and their Application in Rapid Fluorination of Silicon for PET Imaging & Diversification Reactions of γ-Silyl Allenyl Esters to All-carbon Quaternary Stereogenic Centers.
Creator
Jana, Susovan, Lepore, Salvatore D., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
In this dissertation, we discuss the development of new phase transfer agents, which are capable of rapid fluorination of silicon. These are 18-C-6 derivatives containing a hydroxyl group in the side arm (podand), also known as C-pivot lariats. The syntheses of these lariats including several that have not been previously reported and their efficient purification are described. The synthesis route leads to a robust and generalized approach to obtain these lariats on the gram scale. These...
Show moreIn this dissertation, we discuss the development of new phase transfer agents, which are capable of rapid fluorination of silicon. These are 18-C-6 derivatives containing a hydroxyl group in the side arm (podand), also known as C-pivot lariats. The syntheses of these lariats including several that have not been previously reported and their efficient purification are described. The synthesis route leads to a robust and generalized approach to obtain these lariats on the gram scale. These agents were initially designed for applications in positron emission tomography (PET). In this medical imaging modality, tracer agents containing silicon have found promising utility as fluoride receptors for more rapid radiolabeling. Phase transfer agents are generally required for 18F-labeling due to the low solubility in organic reaction media and reactivity of cyclotron-generated [18F]potassium fluoride. We envisioned that 18-C-6 derivatives may serve as both phase transfer agents as well as nucleophilic catalysts (CENCs). In this conception, CENCs were rapidly pre-complexed with KF followed by silicon fluorination, which takes advantage of a previously established silicon dianion mechanism. In collaboration with researchers at the NIH, we studied the effect of various linkers connecting the metal chelating unit to the nucleophilic hydroxyl group on the radiofluorination of silicon under mild condition. A hydrolysis resistant aryl silicon fragment has also been developed that contains various functional groups for convenient attachment to the potential PET radiotracer agents. In a second project, we demonstrate the unique reactivity of γ-silyl allenyl esters. Taking advantage of the silyl group as a fluoride acceptor, these allenoates readily underwent addition to a variety of carbon electrophiles, including aryl fluorides, to afford all-carbon quaternary centers bearing an ethynyl group. Surprisingly, in the presence of aldehydes, exclusive bis-substitution occurs at the γ-position to afford the dicarbinol. Details relating to reaction optimization and substrate scope for both the reactions are presented. Dicarbinol allenes were subsequently converted to highly substituted δ-lactones, a novel 6-hydro-2-pyrone as single diastereomers.
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Date Issued
2018
PURL
http://purl.flvc.org/fau/fd/FA00013073
Subject Headings
Phase-transfer catalysis., Silicon., Positron-Emission Tomography., Crown ethers., Radioactive tracers., Fluorination.
Format
Document (PDF)
New stereoselective reactions to form amido alkyl c-n and vinyl triflate c-o bonds via carbocation intermediates & ultrafast silicon fluorination methodologies for applications in pet imaging
Title
New stereoselective reactions to form amido alkyl c-n and vinyl triflate c-o bonds via carbocation intermediates & ultrafast silicon fluorination methodologies for applications in pet imaging.
Creator
Alhuniti, Mohammed, Lepore, Salvatore D., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
We report here the development of a Lewis acid catalyzed method for the dehydrative coupling of cyclic alcohols and nitriles to form amides with retention of configuration. By contrast, the formation of amides by nitrile trapping of carbocations (Ritter reaction) usually affords racemic product. The present reaction was accomplished by first converting alcohol starting materials to their corresponding chlorosulfites in situ. Even after an extensive search, only copper (II) salts were able to...
Show moreWe report here the development of a Lewis acid catalyzed method for the dehydrative coupling of cyclic alcohols and nitriles to form amides with retention of configuration. By contrast, the formation of amides by nitrile trapping of carbocations (Ritter reaction) usually affords racemic product. The present reaction was accomplished by first converting alcohol starting materials to their corresponding chlorosulfites in situ. Even after an extensive search, only copper (II) salts were able to produce the desired conversion of these chlorosulfites to amides though with low catalytic turnover. Improving the turnover without deteriorating the stereochemical outcome was eventually accomplished by a careful selection of the reagent addition sequence and through the removal of gaseous byproducts. This Ritter-like coupling reaction proceeds in good yields with secondary cyclic alcohols under mild conditions. The stereochemical outcome likely due to fast nucleophilic capture of a non-planar carbocations (hyperconjomers) stabilized by ring hyperconjugation.
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Date Issued
2014
PURL
http://purl.flvc.org/fau/fd/FA00004262
Subject Headings
Intermediates (Chemistry), Nuclear medicine, Organometallic chemistry, Physical organic chemistry, Reaction mechanisms (Chemistry), Tomography, Emission
Format
Document (PDF)
Synthesis and Bioactivity Investigation of Bridged Bicyclic Compounds and a Mechanistic Investigation of a Propargyl Hydrazine Cycloaddition Catalyzed by an Ammonium Salt
Title
Synthesis and Bioactivity Investigation of Bridged Bicyclic Compounds and a Mechanistic Investigation of a Propargyl Hydrazine Cycloaddition Catalyzed by an Ammonium Salt.
Creator
St.Germain, Elijah, Lepore, Salvatore D., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
We report the development of a general route to the synthesis of [4.3.1], [3.3.1], an especially [3.2.1] bicyclic compounds structurally related to vitisinol D, a natural product. This allows for diastereoselective synthesis of bicyclic compounds with five adjacent chiral centers. This route was employed in a preliminary SAR investigation into the neuroprotectant effect of small molecules in an in vivo experiment measuring the degree of restorative effect of synaptic transmission in the...
Show moreWe report the development of a general route to the synthesis of [4.3.1], [3.3.1], an especially [3.2.1] bicyclic compounds structurally related to vitisinol D, a natural product. This allows for diastereoselective synthesis of bicyclic compounds with five adjacent chiral centers. This route was employed in a preliminary SAR investigation into the neuroprotectant effect of small molecules in an in vivo experiment measuring the degree of restorative effect of synaptic transmission in the neuromuscular junction of Drosophila melanogaster larvae under acute oxidative stress. One of the compounds exhibited intriguing potential as a neuroprotectant and outperformed resveratrol in restoring synaptic function under oxidative stress. The hypothesis that bridged bicyclic compounds may hold promise as drug scaffolds due to their conformational rigidity and ability to orient functional appendages in unique orientations is developed. The second focus is a mechanistic investigation into a tetrabutylammoniumcatalyzed cycloaddition as evidence of a novel ammonium-alkyne interaction. A carbamate nitrogen adds to a non-conjugated carbon–carbon triple bond under the action of an ammonium catalyst leading to a cyclic product. Studies in homogeneous systems suggest that the ammonium agent facilitates cyclitive nitrogen–carbon bond formation through a cation–π interaction with the alkyne unit. Using Raman spectroscopy, this cation–π interaction is directly observed for the first time. DFT modeling elucidated the mechanistic factors in this cycloaddition. A teaching experiment was developed based on this mechanistic investigation. Control experiments were employed to demonstrate the testing of two alternative mechanistic hypotheses. Cyclization reactions were performed with a soluble base (sodium phenoxide) with and without tetrabutylammonium bromide under homogeneous conditions. Students observed that ammonium salt accelerates the reaction. They were encouraged to develop a testable hypothesis for the role of the ammonium salt in the cyclization mechanism: typical phase transfer or other. IR spectroscopy was used to directly observe a dose dependent shift of the alkyne stretching mode due to a cation−π interaction. Undergraduates were able to employ the scientific method on a contemporary system and see how data are generated and interpreted to adjudicate between rival hypotheses in a way that emulates authentic and current research in a lab setting.
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Date Issued
2018
PURL
http://purl.flvc.org/fau/fd/FA00013100
Subject Headings
Bicyclic compounds., Ammonium salts., Cycloaddition Reaction.
Format
Document (PDF)
Studies of Alkyne Cycloaddition Reactions Leading to Isoxazolines and Pyrazolines and Synthesis of Urofuranoic Acids to Assess their Effect on Insulin Secretion
Title
Studies of Alkyne Cycloaddition Reactions Leading to Isoxazolines and Pyrazolines and Synthesis of Urofuranoic Acids to Assess their Effect on Insulin Secretion.
Creator
Nagy, Edith, Lepore, Salvatore D., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
The present thesis will be largely focused on identifying and understanding the scope and mechanistic details associated with the tetrabutylammonium fluoride (TBAF) mediated cyclization of alkynyl hydrazines and (O)-hydroxylamines. Also, the synthesis of 2-(2-carboxyethyl)-4-methyl-5-propylfuran-3-carboxylic acid (CMPF) and its analogs will be discussed along with an analysis of their effects on insulin secretion. Chapter 1 will present the importance of developing isoxazoline and pyrazoline...
Show moreThe present thesis will be largely focused on identifying and understanding the scope and mechanistic details associated with the tetrabutylammonium fluoride (TBAF) mediated cyclization of alkynyl hydrazines and (O)-hydroxylamines. Also, the synthesis of 2-(2-carboxyethyl)-4-methyl-5-propylfuran-3-carboxylic acid (CMPF) and its analogs will be discussed along with an analysis of their effects on insulin secretion. Chapter 1 will present the importance of developing isoxazoline and pyrazoline type heterocycles given that they are continually demonstrated to possess a variety of biological activities. Further, the scope of the reaction in terms of functional group tolerability, scalability and mild conditions will be shown. To expand the importance of this work, a route to access non-racemic heterocycles is also noted. With the heterocycles in hand, new methods were developed to generate more complex frameworks in the form of a novel one pot deprotection/functionalization reaction. Chapter 2 will focus on mechanistic investigations of the cyclization. From the initial discovery of the reaction, its actual mechanism was unknown and a main point of interest. What appeared unusual is that a nucleophilic attack occurs on an unactivated triple bond. Given the identity of the products, a reasonable proposal was a 5-endo-dig type cyclization. However, such a pathway would result in the generation of a vinyl anion intermediate which is well known to be of very high energy and it would seem unlikely to occur under mild conditions. Various trapping experiments were used to demonstrate that the vinyl anion forms and a 5-endo-dig-cyclization is the operative mechanism. Chapter 3 analyzes the importance of the tetrabutylammonium fluoride reagent. During optimization studies, it became clear that this base is the ideal reagent to facilitate the cyclization although other bases can also enable the transformation at much slower rates. Addition of non-basic ammonium salt additives to bases such as KF and CsF had a dramatic effect on the rate of the reaction. To determine whether the observed rate differences were merely a phase transfer effect or something more, both empirical and Raman spectroscopy data were collected. Based on this, the first evidence for an ammonium-alkyne cation-pi type interaction was shown. Chapter 4 will summarize the work on the synthesis of 2-(2-carboxyethyl)-4-methyl-5-propylfuran-3-carboxylic acid (CMPF) and its analogs in order to be used in various biological assays. The main goals were to determine a possible structure activity relationship between the substrates and insulin secretion in beta cells and also determine the fate of CMPF in vivo. Several 13C labeled analogs of CMPF were synthesized and successfully used to show for the first time that CMPF in metabolized in vivo in mice.
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Date Issued
2017
PURL
http://purl.flvc.org/fau/fd/FA00004988, http://purl.flvc.org/fau/fd/FA00004978
Subject Headings
Dissertations, Academic -- Florida Atlantic University, Insulin--Secretion., Alkynes., Cycloaddition Reaction., Pyrazolines.
Format
Document (PDF)
Manganese-promoted rearrangement of alkynyl carbonyls to allenyl carbonyls with emphasis on asymmetric induction using chiral bases
Title
Manganese-promoted rearrangement of alkynyl carbonyls to allenyl carbonyls with emphasis on asymmetric induction using chiral bases.
Creator
Khoram, Anita, Florida Atlantic University, Lepore, Salvatore D., Charles E. Schmidt College of Science, Department of Chemistry and Biochemistry
Abstract/Description
The conversion of alkynyl carbonyls to allenyl carbonyls via manganese mediated coordinations followed by a based-catalyzed isomerization was carried out using a range of chiral and achiral amine bases. In this work we employed HPLC equipped with a chiral column to determine the enantiomeric excess. Deuterium labeling experiments suggested that the alkyne/allene rearrangement reaction involved an intermediate cumenolate. We also demonstrated that the reaction required a ligand on manganese...
Show moreThe conversion of alkynyl carbonyls to allenyl carbonyls via manganese mediated coordinations followed by a based-catalyzed isomerization was carried out using a range of chiral and achiral amine bases. In this work we employed HPLC equipped with a chiral column to determine the enantiomeric excess. Deuterium labeling experiments suggested that the alkyne/allene rearrangement reaction involved an intermediate cumenolate. We also demonstrated that the reaction required a ligand on manganese for an amine base to be used catalytically. Phosphines were tested as a possible ligand because they are neutral two electron donors that binds to transition metals through their lone pairs. It was observed that the rate of the reaction decreased from 24hr to 3hr by use of phosphine as a ligand. It was also confirmed that amine base with pKa lower then DBU (pKa = 13.6) would not carry out the isomerization. Chiral amidine and chiral DBU derivatives were synthesized to carry out the isomerization enantioselectively. Alkoxy base were also used in isomerization that demonstrated enantioselectivity.
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Date Issued
2004
PURL
http://purl.flvc.org/fcla/dt/13158
Subject Headings
Carbonyl compounds--Synthesis, Organic compounds--Synthesis, Allene, Alkenes, Methathesis (Chemistry), Isomerism
Format
Document (PDF)
DIASTEREOSELECTIVE ADDITION OF H-PHOSPHINATES TO ALKENYL KETONES UNDER PHASE-TRANSFER CONDITIONS AND SYNTHESIS OF BRIDGED BICYCLIC COMPOUNDS FOR BIOLOGICAL EVALUATION
Title
DIASTEREOSELECTIVE ADDITION OF H-PHOSPHINATES TO ALKENYL KETONES UNDER PHASE-TRANSFER CONDITIONS AND SYNTHESIS OF BRIDGED BICYCLIC COMPOUNDS FOR BIOLOGICAL EVALUATION.
Creator
Yadavalli, Krishna Prasad, Lepore, Salvatore D., Florida Atlantic University, Department of Chemistry and Biochemistry, Charles E. Schmidt College of Science
Abstract/Description
In the present dissertation, we discuss the development of a stereoselective method for the production of phosphorus compounds that utilizes a phospha-Michael addition reaction. Separately, the design and synthesis of compounds that contain an all-carbon bridged bicyclic scaffold is reported; these compounds were used in initial SAR studies in different in vivo models. In Chapter one is presented a mechanistic framework to develop a highly diastereoselective method catalyzed by phase transfer...
Show moreIn the present dissertation, we discuss the development of a stereoselective method for the production of phosphorus compounds that utilizes a phospha-Michael addition reaction. Separately, the design and synthesis of compounds that contain an all-carbon bridged bicyclic scaffold is reported; these compounds were used in initial SAR studies in different in vivo models. In Chapter one is presented a mechanistic framework to develop a highly diastereoselective method catalyzed by phase transfer chemistry leading to phosphinate compounds. In this method, phosphinate nucleophiles were added to various alkenyl ketones as Michael acceptors using crown ethers as phase transfer agents to obtain highly diastereoselective products with the generation of a carbon-based quaternary centers. A closed transition state mechanism is proposed to describe the diastereoselectivity observed in the reactions that is consistent with product outcome as established by X-ray crystallography. Analysis using the 31P NMR technique is also reported to ascertain the diastereomeric ratios in product formation. Using products obtained with the newly developed method, we disclose for the first time a novel phospha-heterocycle with high control of stereochemistry. Relative stereochemistry of the phosphorus containing heterocycle was reported using 2D NMR analysis. In Chapter two focus is placed on the use of acrylates as Michael acceptors in both the diastereoselective and enantioselective studies of phospha-Michael addition. In the asymmetric method development, screening of various chiral catalysts and development of HPLC method to quantify the enantiopurity of products obtained under reaction conditions are reported. The role of crown ether catalysts towards diastereoselectivity is reported.
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Date Issued
2022
PURL
http://purl.flvc.org/fau/fd/FA00014015
Subject Headings
Bridged bicyclic compounds, Chemistry, Organic, Organic compounds--Synthesis
Format
Document (PDF)
RESVERAMORPHS AS PROTECTIVE AGENTS AGAINST EPILEPSY: OPTIMIZATION OF REDUCTIVE ALDOL BICYCLIZATION AND ANALOG SYNTHESIS WITH FUNCTIONAL GROUP VARIATION TO ASSESS IMPACT ON BIOACTIVITY
Title
RESVERAMORPHS AS PROTECTIVE AGENTS AGAINST EPILEPSY: OPTIMIZATION OF REDUCTIVE ALDOL BICYCLIZATION AND ANALOG SYNTHESIS WITH FUNCTIONAL GROUP VARIATION TO ASSESS IMPACT ON BIOACTIVITY.
Creator
Jutte, Elyse M., Lepore, Salvatore D., Florida Atlantic University, Department of Chemistry and Biochemistry, Charles E. Schmidt College of Science
Abstract/Description
This work encompasses the synthesis, analysis, and optimization of [3.2.1] all-carbon bridged bicyclic compounds, known as resveramorphs (RVM), Studies were conducted using a Caenorhabditis elegans model, where RVMs were tested for antiseizure capabilities. In both applications, RVMs proved potent with activities in the sub-nanomolar level in one case. A structure-activity relationship (SAR) was hypothesized for the identification of the pharmacophore. The six to seven step synthesis route...
Show moreThis work encompasses the synthesis, analysis, and optimization of [3.2.1] all-carbon bridged bicyclic compounds, known as resveramorphs (RVM), Studies were conducted using a Caenorhabditis elegans model, where RVMs were tested for antiseizure capabilities. In both applications, RVMs proved potent with activities in the sub-nanomolar level in one case. A structure-activity relationship (SAR) was hypothesized for the identification of the pharmacophore. The six to seven step synthesis route towards the RVM analogues is discussed in further detail. The bicyclization of the RVMs is achieved through a reductive aldol reaction. The reaction suffers from selectivity issues leading to multiple bicyclic products. By following a one-factor-at-a-time (OFAT) methodology, attempts at optimization for this reaction were made, however, despite important gains, the overall yields of the bicyclic product remain low. Other products from this reaction have been used to understand the reaction mechanism, which will be the basis for future efforts to further optimize this key step.
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Date Issued
2023
PURL
http://purl.flvc.org/fau/fd/FA00014288
Subject Headings
Epilepsy--Animal models, Bridged Bicyclo Compounds, Resveratrol
Format
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Base Promoted 5-endo-dig Cyclizations of Non-Conia-ene Propargyl Ethers: A Mechanistic Investigation
Title
Base Promoted 5-endo-dig Cyclizations of Non-Conia-ene Propargyl Ethers: A Mechanistic Investigation.
Creator
Hintze, Silas Q., Lepore, Salvatore D., Florida Atlantic University, Department of Chemistry and Biochemistry, Charles E. Schmidt College of Science
Abstract/Description
Herein, we discuss a novel method for the synthesis of decorated 2,5-dihydrofurans. The base promoted 5-endo-dig cyclization of non-Conia-ene propargyl ethers produces 2,2 disubstituted dihydrofurans. Central to the reaction is the presence of an acidic C–H bond which is activated by an adjacent aromatic heterocycle. The transformation is viable with a wide range of substituents, including N, O, and S containing heterocycles, substituted phenyl rings, and alkyl groups. The cyclization...
Show moreHerein, we discuss a novel method for the synthesis of decorated 2,5-dihydrofurans. The base promoted 5-endo-dig cyclization of non-Conia-ene propargyl ethers produces 2,2 disubstituted dihydrofurans. Central to the reaction is the presence of an acidic C–H bond which is activated by an adjacent aromatic heterocycle. The transformation is viable with a wide range of substituents, including N, O, and S containing heterocycles, substituted phenyl rings, and alkyl groups. The cyclization proceeds within 30 seconds at room temperature under the action of potassium tert-butoxide. This work stands apart from the current literature due to the absence of transition metal catalysts and/or harsh reaction conditions. A thorough mechanistic investigation is undertaken to better understand the nature of this unprecedented reaction.
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Date Issued
2024
PURL
http://purl.flvc.org/fau/fd/FA00014376
Subject Headings
Cyclization (Chemistry), Chemistry, Organic
Format
Document (PDF)