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@PHDTHESIS{Mendel:991092,
author = {Mendel, Marvin},
othercontributors = {Schoenebeck, Franziska and Leonori, Daniele and Patureau,
Frederic W.},
title = {{M}odular {P}d$^{({I})}$ cross-coupling strategies and
original {N}i$^{({I})}$ metalloradical catalysis},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2024-07678},
pages = {1 Online-Ressource : Illustrationen},
year = {2024},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, RWTH Aachen University, 2024},
abstract = {Homogeneous metal catalysis has revolutionized modern
organic synthesis. Traditionally, most reported methods have
focused on closed-shell two-electron processes involving
mononuclear species, e.g. Pd(0)/Pd(II) cycles. In contrast,
processes involving dimeric metal complexes in rather
unusual oxidation states like Pd(I) have – by comparison
– received much less attention. In the context of this
thesis, dinuclear palladium(I) and nickel(I) complexes were
studied. Traditionally, such dinuclear scaffolds were
utilized as precursors for highly reactive, low-valent
mononuclear species. However, our group found strong
evidence for dinuclear Pd(I) reactivity and mononuclear
Ni(I) metalloradical catalysis.The modular assembly of
standardized building blocks is a powerful way to generate
diverse molecules quickly. However, to make this approach
more widely applicable, the generality of the coupling
methodology is critical. The first chapter of this thesis
discusses a new modular coupling method that complements the
existing strategy of boron-containing precursors. Our
approach uses polyfunctionalized organogermane-containing
building blocks that display orthogonal reactivity towards
Pd(I)-catalyzed cross-coupling conditions. The organogermane
moiety itself is unreactive towards Pd(I) dimer bond
construction but can act as a masked halide functionality
that can be revealed in an electrophilic unmasking event.
This method significantly shortens reaction times for
iterative coupling steps and allows for the creation of
linear iodinated polyarenes, which were previously
inaccessible via modular cross-coupling. Furthermore, the
recycling of the germanium handle was showcased, improving
the methodology's sustainability. Vinylcyclopropanes are
functional handles with significant value in mechanistic
studies, drugs, and natural products. They are also used as
precursors for various synthetic transformations. However,
their reactive nature makes their installation through
catalytic approaches challenging. In this context, chapter
two highlights the development of a modular and
stereoretentive method for installing (di)vinylcyclopropanes
under mild conditions. This method enables access to cis or
trans cyclopropane and E or Z vinyl-stereochemical
relationships. The process relies on air-stable dinuclear
Pd(I) catalysis, allowing rapid and highly selective access
to a diverse range of vinylcyclopropane motifs at room
temperature within 30 minutes. The efficiency has been
showcased in the synthesis of the naturally occurring
Dictyopterenes found in brown algae. Traditionally, organic
free radicals, upon addition to a vinylcyclopropane, lead to
rapid ring-opening under strain release. This transformation
is widely used as a mechanistic probe for the intermediacy
of radicals. However, the last chapter of my thesis has
revealed a new perspective. A Ni(I) metalloradical triggers
reversible cis/trans-isomerization instead of opening
towards the thermodynamic equilibrium. This isomerization
proceeds under chiral inversion and is remarkably rapid and
mild. The extensive mechanistic studies support novel
metalloradical reactivity, and key mechanistic features were
revealed, such as the reversibility of the process. The new
approach has been applied in two protocols: a dynamic
thermodynamic resolution strategy of a valuable
pharmaceutical building block and a trans-to-cis
isomerization-tandem Cope rearrangement strategy.},
cin = {152110 / 150000},
ddc = {540},
cid = {$I:(DE-82)152110_20160701$ / $I:(DE-82)150000_20140620$},
pnm = {MetalloRadiCat - Metalloradical Catalysis - From
Fundamental Studies to Applications (864849)},
pid = {G:(EU-Grant)864849},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2024-07678},
url = {https://publications.rwth-aachen.de/record/991092},
}
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