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Rueda Espinosa, Juan Manuel

University of British Columbia

This thesis explores the activation of C−H, C−F, and C−S bonds by group 10 transition metals, the findings presented in this work offer a foundation for designing catalytic systems where the selective cleavage of C−H, C−F, and C−S bonds plays a pivotal role in the catalytic cycle. In Chapter 1, we review the relevant literature on C−H bond activation by Pt, C−F bond activation by Ni, and C−S bond activation by Pd. We identify three key gaps in these fields: (1) the limited mechanistic understanding of Csp³−H activation at Ptᴵⱽ, (2) the absence of a desulfonative Suzuki-Miyaura coupling (SMC) of aryl sulfonyl fluorides that is air- and water-tolerant, and (3) the need for a deeper understanding of the mechanism underlying nickel-catalyzed C−F activation and the cross-coupling of polyfluorinated aromatic imines. In Chapter 2, we present an example of Csp³−H activation at Ptᴵⱽ via aerobic oxidation of (DPEOH)PtMe₂, (DPEOH = 1,1-di(2-pyridyl)ethanol). DFT calculations highlight the proton-responsive ligand as critical for kinetic control over the formation of Ptᴵⱽ−OH intermediates, which are essential for a concerted metalation deprotonation (CMD)-like C−H activation. The role of the trans-influence of Me, F and Cl ligands in this Csp³−H activation step is examined. In Chapter 3, we describe a Pd(dppf)Cl₂-catalyzed SMC reaction of 2-pyridylsulfonyl fluoride with hetero(aryl) boronic acids and pinacol esters. This methodology was shown to tolerate water and oxygen, and delivers competitive results with certain boronic esters. Notably, water as a cosolvent improved yields when pinacol esters were used, while its effect was substrate-dependent with boronic acids. In Chapter 4, we discuss the challenges observed while studying the mechanism of Ni-catalyzed C−F activation and cross-coupling in polyfluorinated aromatic imines, and we study the nickel coordination environment under the reaction conditions by DFT calculations. The Negishi coupling of the abovementioned substrates showed inconsistent yields, and the SMC led to several C−F functionalization reactions, contradicting the reported selectivity. Additionally, DFT studies were performed on the speciation of mixtures containing Ni(COD)₂, PPh₃ and fluorinated aromatic imines, revealing that π-η² C=N is the favored coordination mode in aromatic imines, with increasing fluorination further promoting this coordination mode.

Text

2025-02-13

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/90363

Chemistry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/