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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Catalytic Enantioselective Synthesis of Secondary Organoboronates and Progress Towards the Total Synthesis of Sarcodictyins:

Hu, Weipeng January 2022 (has links)
Thesis advisor: James P. Morken / This dissertation will present three main projects focusing on the transition metal-catalyzed enantioselective synthesis of secondary organoboronic esters and progress towards the total synthesis of sarcodictyins. In the first project, a palladium-catalyzed enantioselective conjunctive cross-coupling reaction with propargylic electrophiles will be described. The tetra-substituted allenes are isolated with good yield and enantioselectivity and the beneficial effects of alcohol additives are investigated. The second project describes the enantioselective synthesis of ɑ-boryl zinc reagents by a nickel-catalyzed carbozincation reaction. The in situ generated ɑ-boryl zinc intermediate can be trapped by copper-mediated allylations, palladium-catalyzed Negishi cross-couplings, and cerium-mediated halogenation reactions to construct various chiral organoboranes. The synthetic utility of this methodology is showcased by the synthesis of natural products, including bruguierol A, (-)-aphanorphine, and (-)-enterolactone. The mechanism is studied with the assistance of EPR and deuterium-labeling experiments and a catalytic cycle through a Ni(I) intermediate is proposed. The third project depicts a synthetic route to essential precursors in the progress of the total synthesis of sarcodictyins. Various attempts to construct the ten-membered ring core of sarcodictyin have been made, including Sonogashira reaction, Dieckmann condensation, and lithium—halogen exchange process. / Thesis (PhD) — Boston College, 2022. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
2

Nonracemic Organoboronates by Transition Metal-Catalyzed C-C and C-Si Bond Forming Reactions

Szymaniak, Adam Anthony January 2018 (has links)
Thesis advisor: James P. Morken / This dissertation will describe the development of three transition metal-catalyzed syntheses of nonracemic organoboronates. The first chapter explains the development of a palladium-catalyzed enantiotopic-group-selective cross-coupling of geminal bis(boronates) with alkenyl electrophiles. This process enables the synthesis of highly valuable nonracemic disubstituted allylic boronates. Chapter two describes a palladium-induced 1,2-metallate rearrangement of vinylboron “ate” complexes. The newly developed process incorporates an alternative route for the transmetallation step of Suzuki-Miyaura cross-couplings. Lastly, an enantioselective platinum-catalyzed hydrosilylation of alkenyl boronates is disclosed. This reaction enables the synthesis of nonracemic geminal silylboronates for the divergent synthesis of functionalized / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
3

Preparation of Organoboronates through Nickel-Catalyzed Conjunctive Coupling Reactions and Their Applications:

Koo, Seung Moh January 2020 (has links)
Thesis advisor: James P. Morken / This thesis will describe the development of two transition metal catalyzed syntheses of organoboronic compounds. The first section describes relevant concepts and precedents for the conjunctive coupling reaction. In the second section of this thesis, nickel catalyzed conjunctive coupling reaction of carboxylic acid derivatives with 9-BBN derived ate complexes will be discussed, where beta-trialkylboryl ketones are obtained as the product. In the third section, the development of alkyl group migration in nickel-catalyzed conjunctive coupling with C(sp3) electrophiles will be discussed. Enantioenriched secondary boronic esters can be prepared from this reaction, and two alkaloid syntheses are disclosed as the application of the method. / Thesis (MS) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
4

Catalytic Conjunctive Cross-Coupling and Catalytic Diboration Reactions

Zhang, Liang January 2017 (has links)
Thesis advisor: James P. Morken / This dissertation will present four main projects focused on stereoselective construction of borylated compounds as well as their applications in asymmetric syntheses. The first two projects describe the development of a catalytic conjunctive cross-coupling reaction. By merging three simple starting materials, an organolithium reagent, an organoboronate, and an organic electrophile, a synthetically valuable secondary boronate is furnished by the conjunctive cross-coupling in an efficient and enantioselective fashion. Next, this strategy is expanded to synthesize severely hindered tertiary boronates, a synthetic challenging but powerful building block to access a variety of quaternary stereocenters. The third project presents a platinum-catalyzed enantioselective diboration of alkenyl boronates to furnish a broad range of 1,1,2-tris(boronates) products. A deborylative alkylation of the 1,1,2-tris(boronates) leads to a variety of internal vicinal bis(boronates) with high diastereoselectivity. In the final chapter, a general and practical synthesis of alkenyl boronates via the boron-Wittig reaction is disclosed. Utilizing readily accessible geminal bis(boronates) and aldehydes, a broad range of disubstituted and trisubstituted alkenyl boronates are afforded with good yield and stereoselectivity. / Thesis (PhD) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

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