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New Boron–Hydrogen Insertion Reactions of Ligated Boranes

Allen, Thomas (2018) New Boron–Hydrogen Insertion Reactions of Ligated Boranes. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Chemical transformations of ligated borane complexes, including N-heterocyclic carbene boranes, are demonstrated. Chapter 1 begins with an introduction of Lewis base borane complexes, rhodium carbene chemistry, and B–H insertion of ligated boranes. The second part of Chapter 1 describes the insertion of rhodium carbenes, previously demonstrated with NHC-boranes, into the B–H bonds of other ligated boranes. Stable ligated α-boryl esters were isolated. A series of competitive B–H insertion experiments are described that were used to develop a relative reactivity profile of ligated boranes toward rhodium-catalyzed B–H insertion. The enantioselective B–H insertion of NHC-boranes with chiral dirhodium catalysts was also investigated. Finally, the synthesis and application of two chiral bridged dirhodium catalysts is described.
Chapter 2 describes the discovery and isolation of NHC-boryl hydrazones by non-chain radical recombinations of NHC-boranes, diazomalonates, and azo initiators. Thermal 1,1-hydroborations of a diazo dione and a diazonium salt to give boryl hydrazone and boryl diazene products are demonstrated. Chapter 3 explores the use of electrophilic NHC-borane complexes to catalyze B–H insertion reactions with diazoesters. The boryl iodide catalyzed method is adept at producing α-substituted-α-NHC-boryl esters. A small family of NHC-boryl esters with amino acid side chains was synthesized. Chapter 4 describes the basic hydrolyses of ligated α-boryl esters to yield ligated α-boryl acetic acids. The boryl acetic acid derivatives were characterized by X-ray crystallography and acidity constant measurements. They are among the least acidic carboxylic acids known. The electron-donating ability of ligated borane substituents was further quantified by using derived Hammett constants from 13C NMR chemical shift correlation experiments.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Allen, ThomasTHA14@pitt.eduTHA140000-0002-6624-9234
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairCurran,
Committee MemberBrummond,
Committee MemberHorne,
Committee MemberShiva,
Date: 26 September 2018
Date Type: Publication
Defense Date: 17 July 2018
Approval Date: 26 September 2018
Submission Date: 26 July 2018
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 180
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Borenium
Date Deposited: 26 Sep 2018 19:39
Last Modified: 26 Sep 2018 19:39


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