Allen, Thomas
(2018)
New Boron–Hydrogen Insertion Reactions of Ligated Boranes.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
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Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
|
| 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 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/34993 |
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