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@PHDTHESIS{Ascheberg:740216,
author = {Ascheberg, Christoph},
othercontributors = {Niggemann, Meike and Enders, Dieter},
title = {{E}ninole in {C}alcium-katalysierten
{C}ycloisomerisierungsreaktionen und {B}or-vermittelte
elektrophile {A}minierung von {N}itroverbindungen},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2018-228483},
pages = {1 Online-Ressource (ix, 276 Seiten) : Illustrationen},
year = {2018},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, RWTH Aachen University, 2018},
abstract = {During this work experiments on two different fields in
organic chemistry were carried out. In the first field,
concerning cycloisomerisation reactions, the synthesis of
complex structures out of simple 1,6-enynols was achieved
with the help of a calcium catalyst developed in the
Niggemann group. Based on a previously published calcium
catalyzed cyclopropanation reaction, the equilibrium between
a homoallenyl cation and his cyclopropyl congener was
exploited. In a first project the homoallenyl cation was
intercepted with different aldehydes to yield dihydro
pyranes. Mechanistic studies allowed to propose two possible
mechanistic scenarios for this transformation. In a second
project the vinyl cation present in the cyclopropyl congener
was stabilized via the introduction of an adjacent ether
function. This allowed reaction of the vinyl cation with
water as a nucleophile, yielding highly substituted
cyclopentane derivatives. A strong influence of different
groups on the reactivity of the enynol starting material was
observed. After modification of the enynol substrates, the
reaction of the homoallenyl cation with different
nucleophiles was enabled. That is how the synthesis of
exocyclic allenes was realized in another project. All of
the mentioned reactions provide a greener and more
sustainable alternative to previously know transition metal
catalyzed reactions. The second field was concerned with the
electrophilic amination of nitroarenes. In a first project,
aromatic nitro compounds were transformed to functionalized
amines via the reaction with a B2pin2-zinc organyl system. A
two step partial reduction of the nitro moiety, lead to the
formation of a nitronate and then a nitrenoid. This
nitrenoid was used as electrophilic amination reagent for
zinc organyls, yielding aminoboranes. These could be reacted
with different electrophiles. Exhaustive mechanistic studies
were carried out using in situ 11B-NMR and control
experiments. A great variety of nitroaromatics, zinc
organyls and electrophiles could be used for this reaction.
In a second project, the reaction principle was transferred
to aliphatic nitro compounds. The intermediacy of highly
reactive nitroso compounds which are in equilibrium with the
corresponding oxime and often entangled in side reactions
was avoided. That is how also aliphatic nitro compounds
could be converted to functionalized amines in high yields
for the first time. The scope of nitro compounds and zinc
organyls was broad for the aliphatic nitro compounds as
well. In a third project the aminoboranes synthesized from
nitroaromatics were reacted with carbenoids, yielding
formanilides in low yields.},
cin = {152920 / 150000},
ddc = {540},
cid = {$I:(DE-82)152920_20140620$ / $I:(DE-82)150000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2018-228483},
url = {https://publications.rwth-aachen.de/record/740216},
}
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