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You searched for subject:(oxazinanes). Showing records 1 – 2 of 2 total matches.

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University of South Florida

1. Nimmagadda, Sri Krishna. Asymmetric Transformations Catalyzed By Chiral BINOL Alkaline Earth Metal Phosphate Complexes.

Degree: 2016, University of South Florida

Small molecule hydrogen bond donors have emerged as versatile catalysts in asymmetric synthesis. Within this class, chiral BINOL phosphoric acid is regarded as one of the pioneer catalysts used in several asymmetric transformations. The ability of the catalyst to activate the substrates could be controlled in two different ways. (1) Dual activation/bifunctional activation of substrate by hydrogen bond interactions or ion pairing with phosphoric acid or (2) By forming chiral BINOL phosphate metal complex that could significantly alter the interactions in chiral space. In particular, chiral alkaline earth metal phosphate complexes have unique advantages as catalysts owing to the ubiquitous availability of alkaline earth metals, strong Brønsted basicity of their counterions, mild but significant Lewis acidity of the metal and their ability to coordinate at multiple reactive sites due to large ionic radius. Chapter 1 summarizes the recent development of alkaline earth metal complexes in asymmetric catalysis. My thesis dissertation is focused on the application of chiral alkaline earth metal phosphate complexes in novel asymmetric reactions. In Chapter 2, we disclosed an efficient asymmetric one-pot synthesis of chiral 1,3-oxazolidines and chiral 1,3-oxazinanes. Chiral oxazolidines and oxazinanes are widely used as auxiliaries in asymmetric transition metal catalysis and also key structural motifs in natural products with biological activities. We developed a new synthetic method for chiral 1,3-oxazolidines which follows the enantioselective addition of alcohols to imines catalyzed by chiral 3,3’-(triisopropylphenyl)-derived BINOL magnesium phosphate to form hemiaminal intermediate, which then undergoes mild base mediated intramolecular nucleophilic substitution to afford highly enantioselective 1,3-oxazolidines and 1,3-oxazinanes in good yields. In Chapter 3, we developed the first catalytic enantioselective desymmetrization process for the synthesis of novel axially chiral cyclohexylidene oxime ethers. Even though these molecules were found to be optically active in 1910, methods to synthesize these molecules are scarce. We have developed an efficient desymmetrization process of 4-phenyl cyclohexanones with phenoxyamines catalyzed by chiral BINOL strontium phosphate complex to afford highly enantioselective products. We then extended this methodology to the dynamic kinetic resolution of 2-substituted cyclohexanones to form chiral 2-substituted cyclohexyl oximes in good enantioselectivities, as demonstrated in Chapter 4. We further demonstrated the utility of these compounds by converting them to chiral 2-aryl cyclohexylamines which are important synthetic intermediates.

Subjects/Keywords: asymmetric catalysis; organocatalysis; chiral alkaline earth metal phosphate; oxazolidines; oxazinanes; hemiaminals; desymmetrization; dynamic kinetic resolution; Chemistry; Organic Chemistry

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APA (6th Edition):

Nimmagadda, S. K. (2016). Asymmetric Transformations Catalyzed By Chiral BINOL Alkaline Earth Metal Phosphate Complexes. (Thesis). University of South Florida. Retrieved from https://scholarcommons.usf.edu/etd/6554

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Nimmagadda, Sri Krishna. “Asymmetric Transformations Catalyzed By Chiral BINOL Alkaline Earth Metal Phosphate Complexes.” 2016. Thesis, University of South Florida. Accessed September 23, 2020. https://scholarcommons.usf.edu/etd/6554.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Nimmagadda, Sri Krishna. “Asymmetric Transformations Catalyzed By Chiral BINOL Alkaline Earth Metal Phosphate Complexes.” 2016. Web. 23 Sep 2020.

Vancouver:

Nimmagadda SK. Asymmetric Transformations Catalyzed By Chiral BINOL Alkaline Earth Metal Phosphate Complexes. [Internet] [Thesis]. University of South Florida; 2016. [cited 2020 Sep 23]. Available from: https://scholarcommons.usf.edu/etd/6554.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Nimmagadda SK. Asymmetric Transformations Catalyzed By Chiral BINOL Alkaline Earth Metal Phosphate Complexes. [Thesis]. University of South Florida; 2016. Available from: https://scholarcommons.usf.edu/etd/6554

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

2. Baldwin, Andrea Michelle. Synthesis and Functionalization of Heterocycles via Non-Covalent Catalysis.

Degree: PhD, Chemistry, 2016, The Ohio State University

Hydrogen-bond donor (HBD) catalysis has emerged as a remarkable platform for the activation of reactants through non-covalent interactions. This class of organocatalysts provides a sustainable alternative to transition metal catalysis and avoids the difficulties associated with trace metal removal. Classically, HBD catalyst interactions proceed in two major pathways: direct activation or anion recognition. Enhanced HBD catalysts that display improved performance under both modes of action allow for the discovery of new reactivity patterns that have previously been unattainable. Two new classes of elegantly designed non-covalent catalysts have been explored in the synthesis and functionalization of heterocycles.Boronate ureas, an internal Lewis acid assisted urea, are particularly well suited for the direct activation of molecules containing nitro-functionality. Donor-acceptor cyclopropanes are useful building blocks in synthetic chemistry due to the electronic nature of the strained ring and the intrinsic functionality. Boronate ureas were applied toward development of the first cycloaddition of nitrones with nitrocyclopropane carboxylates in the presence of an enhanced non-covalent catalyst. The highly functionalized 1,2-oxazinane core synthesized in this single step is a prominent scaffold in many bioactive targets. With this strategy, a small library of oxazinane products has been synthesized in up to 99% yield and 4:1 dr. A second class of enhanced catalysts, silanediols, have a propensity to recognize the ether functionality. This molecular recognition was exploited in the context of direct epoxide activation for carbon dioxide fixation. Typically, with organocatalytic cyclic carbonate formation, very few types of functional groups are able to affect this transformation under mild conditions; often, high temperatures, long reaction times, and high pressures of carbon dioxide are necessary for desired product formation. With only 10 mol % of a silanediol-tetrabutylammonium iodide co-catalyst system, this transformation can be accomplished at room temperature using only one bar of carbon dioxide.Having established the ability of silanediols to work in tandem with anions, chiral silanediols were investigated in enantioselective anion-binding catalysis to construct chromanones. To date, introduction of carbonyl-containing nucleophiles in an intermolecular fashion has only been performed racemically. However, the unique chemical environment accessible with novel chiral silanediols is able to control carbon-carbon bond formation between silyl ketene acetals and benzopyrylium salts generated in situ from chromone derivatives. When coupled with recrystallization, synthetically useful enantioselectivities of up to 74% can be obtained. Importantly, this is the first example of anion-binding catalysis utilizing the benzopyrylium ions of chromenones, as well as an innovative strategy to incorporate complex alkyl functionality directly into the scaffold of chromanones. Advisors/Committee Members: Mattson, Anita (Advisor).

Subjects/Keywords: Organic Chemistry; organocatalysis; hydrogen bond donor catalysis; silanediols; boronate ureas; oxazinanes; carbonates; chromanones; asymmetric catalysis

…Urea-catalyzed Construction of Oxazinanes " Org. Biomol. Chem. 2013, 11, 5793–5797… …30 1.5.6 Procedures and Characterization for Further Transformations of Oxazinanes 42… …23 Scheme 1.9 Additional Transformation of Oxazinanes… …So, S. S.; Mattson, A. E. "Urea-Catalyzed Construction of Oxazinanes " Org… …reactions with D-A cyclopropanes and nitrones to prepare tetrahydro-1,2-oxazinanes are highlighted… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Baldwin, A. M. (2016). Synthesis and Functionalization of Heterocycles via Non-Covalent Catalysis. (Doctoral Dissertation). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1467277822

Chicago Manual of Style (16th Edition):

Baldwin, Andrea Michelle. “Synthesis and Functionalization of Heterocycles via Non-Covalent Catalysis.” 2016. Doctoral Dissertation, The Ohio State University. Accessed September 23, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1467277822.

MLA Handbook (7th Edition):

Baldwin, Andrea Michelle. “Synthesis and Functionalization of Heterocycles via Non-Covalent Catalysis.” 2016. Web. 23 Sep 2020.

Vancouver:

Baldwin AM. Synthesis and Functionalization of Heterocycles via Non-Covalent Catalysis. [Internet] [Doctoral dissertation]. The Ohio State University; 2016. [cited 2020 Sep 23]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1467277822.

Council of Science Editors:

Baldwin AM. Synthesis and Functionalization of Heterocycles via Non-Covalent Catalysis. [Doctoral Dissertation]. The Ohio State University; 2016. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1467277822

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