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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

Regio- and Stereo- selective Methods for the Borylation of Substituted Alkynes

Bowen, Johnathan 09 March 2023 (has links)
Organoboron derivatives represent an important class of compounds due to the versatility of the carbon-boron bond in a variety of chemical reactions. Boron-containing compounds have garnered increasing attention as synthetic intermediates and medicinal agents. Therefore, the introduction of carbon-boron bonds to organic molecules continues to be an important field of study. This dissertation describes novel methodology for the regio- and stereo-selective introduction of carbon-boron bonds to generate β-borylacrylonitrile and 1-boryl-1,3-enyne products. Propiolonitriles are intriguing research targets due to the electron-withdrawing nature of the cyano group on the adjacent alkyne. In this dissertation, we developed a phosphine-catalyzed regio- and stereo-selective hydroboration of propiolonitriles to generate novel β-borylacrylonitriles in up to 89% yield and 97:3 (E)-selectivity. These products were converted to the corresponding postassium 1,2-vinylcyanotrifluoroborate salts and demonstrated applications in oxidation and Suzuki-Miyaura cross-coupling reactions. Interestingly, 31P and 13C NMR studies suggest that this hydroboration reaction proceeds in a 1,2-phosphine addition pathway instead of a canonical 1,4-conjugate addition pathway. We also developed a transition metal-free cis hydroboration of 1,3-diyne substrates. In the presence of catalytic amounts of tri-n-butylphosphie and the unsymmetric diboron reagent pinBBdan, 1-boryl-1,3-enyne products were generated in up to 63% and >99:1 (Z)-selectivity. These 1,8-diaminonaphthalene products can be converted to the corresponding pinacolboranes or trifluoroborate salts. They also demonstrated applications in protodeboronation and Suzuki-Miyaura cross-coupling reactions. We propose that this hydroboration occurs via a nucleophilic boron addition mechanism. / Doctor of Philosophy / Incorporating boron into organic molecules provides access to a variety of otherwise difficult chemical reactions. Therefore, our laboratory seeks to develop new methods for synthesizing organoboron compounds. A major goal of our work is to develop transition metal-free reactions due to the expense and environmental impact of transition-metal mediated methodology. This dissertation reports two new methods for installing boron to organic molecules without the use of transition metals. The reported reactions utilize mild conditions to selectively generate functionalized products, and applications of these products are demonstrated. Chapter 1 describes a hydroboration reaction of propiolonitrile derivatives to afford (E)-β-borylacrylonitrile products. Notably, this reaction proceeds via a unique mechanism, contrasting that of similar reported reactions. Chapter 2 reports a transition metal-free hydroboration of 1,3-diynes to afford (Z)-1-boryl-1,3-enyne products. These products are structurally similar to relevant molecules in medicinal, polymer, and synthetic chemistry.

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