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@PHDTHESIS{Hamad:1015641,
author = {Hamad, Aboubakr},
othercontributors = {Ritter, Tobias and Bolm, Carsten and Herres-Pawlis, Sonja},
title = {{D}ual remote {C}-{H} functionalization using aryl
sulfonium salts $\&$ applications of ruthenium η6-arene
complexes},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2025-06496},
pages = {1 Online-Ressource : Illustrationen},
year = {2025},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, RWTH Aachen University, 2025},
abstract = {Summary: In this thesis, advanced strategies for
regioselective aromatic C–H functionalization via the
formation of aryl sulfonium salts and transition metal
catalysis were explored. Additionally, catalytic and
stoichiometric π-arene activation, using ruthenium phenoxo
complexes, was explored. The work is divided into two
sections: Double C–H Functionalization Using Aryl
Sulfonium Salts Methods for site-selective C–H
functionalization provide a powerful approach to increase
the structural complexity of organic compounds. Significant
efforts have been devoted to developing novel strategies for
the directed and selective functionalization of C–H bonds.
For example, iridium-catalyzed borylation of arenes has
become a valuable tool in modern organic synthesis. However,
its selectivity is determined mainly by substitution
patterns or the presence of specific directing groups. On
the other hand, aromatic C–H functionalization via
thianthrenation reaction offers excellent para-selectivity
for mono-substituted arenes independent of the presence of a
directing group. However, the thianthrenation reaction is
limited to the functionalization of a single position on the
arene. The first section of this thesis presents an approach
to regioselective double C–H functionalization. A
sulfoxide-tethered to a directing group was employed in the
synthesis of aryl sulfonium salts via electrophilic aromatic
substitution (SEAr). Subsequently, the directing group was
used in directed C–H functionalization, where oxidative
Heck coupling was achieved. Afterwards, the sulfonium moiety
served as a linchpin for subsequent Sonogashira coupling.
The reaction conditions were optimized, and the reaction
demonstrated regioselective double C–H functionalization
of simple arenes. Applications of Ruthenium η6–Arene
Complexes with Phenoxo Ligandsπ-Arene activation through
facial coordination to a transition metal significantly
changes the electronic properties of the coordinated arene
from an electron-rich to an electron-poor arene. This
‘‘umpolung’’ of arene reactivity has been utilized
with various rhodium and ruthenium complexes to facilitate
otherwise unattainable transformations without η6–arene
coordination to a transition metal. Various ruthenium
complexes rely on cyclopentadienyl (Cp) ancillary ligands,
which exhibit low arene exchange rates. Consequently, the
slow arene exchange associated with Cp-supported ruthenium
complexes has resulted in limited reactivity. The second
section of this work explored the reactivity of ruthenium
phenoxo complexes in the hydrolysis of fluoroarenes,
deoxyfluorination, and catalytic decarboxylation reactions.
Ruthenium phenoxo complexes were synthesized and evaluated
for their reactivity with aryl fluorides, phenols and
phenylacetic acid derivatives. Key findings
include:Hydrolysis of Fluoroarenes: Stoichiometric
conversion of facially coordinated fluoroarenes to phenols
was achieved, though the reaction was limited to simple
substrates and required elevated temperatures and long
reaction times. Benzylic Decarboxylation: Catalytic
decarboxylation of phenylacetic acid derivatives proceeded
efficiently via π-arene activation, but the methodology was
not applicable to substrates with strong donor groups or
increased steric hindrance. Mechanistic studies offered
insights into the reaction pathways. For example, the
involvement of η6–coordinated intermediates in
decarboxylation and hydrolysis reactions were established.
The reactivity trends observed in ruthenium-catalyzed
transformations provided a deeper understanding of
metal-arene chemistry and expanded the utility of these
complexes in organic synthesis. Overall, this thesis
demonstrates the potential of transition-metal catalysis and
tailored intermediates in enabling selective C–H
functionalization. Additionally, the second part has shown
potential application for π-arene activation using
ruthenium supported by phenoxo ligands. The findings
contribute to advancing efficient synthetic methodologies,
addressing challenges in the activation and transformation
of inert bonds.},
cin = {152310 / 150000},
ddc = {540},
cid = {$I:(DE-82)152310_20140620$ / $I:(DE-82)150000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2025-06496},
url = {https://publications.rwth-aachen.de/record/1015641},
}
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