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%0 Thesis
%A Gevondian, Avetik
%T Site-selective, orthogonal functionalization of organogermanes, and “batch-forbidden” transformations enabled in cyclic flow mode
%I RWTH Aachen University
%V Dissertation
%C Aachen
%M RWTH-2025-01329
%P 1 Online-Ressource : Illustrationen
%D 2024
%Z Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2025
%Z Dissertation, RWTH Aachen University, 2024
%X In many aspects utilization of transition metals in cross-coupling reactions turned out to be huge progress in synthetic chemistry methodology and proved itself as a reliable approach towards synthesis of complex and important organic molecules for agrochemistry, pharmaceuticals and other vital fields. Nowadays, a wide range of nucleophiles were developed and investigated as coupling partners, but none of them is able to show orthogonality in different cross-coupling reactions. This thesis describes reactivity of a relatively novel agent, aryl germanes, in completely different transformations as a robust, highly reactive and orthogonal species prevailing reactivity of other known functionalities, such as halogens, silanes and boronic acid esters. The first part of the thesis is dedicated to selective Au-catalyzed arylation of aryl germanes with diazonium salts. Previous studies of our group showed effective C-H arylation of organogermanes with simple arenes supported by Au(I)/Au(III) catalytic cycle. The reaction requires stoichiometric amounts of an oxidant, which reduces atom economy and produces stoichiometric amounts of waste. Combination of high oxidative potential and an ability to play a role of a cross-coupling agent allows diazonium salts to provide cleaner Au(I)/Au(III)-catalyzed arylation of aryl germanes with light assistance. Transformation appeared highly selective towards C-Ge bond ignoring all other potentially reactive sites. We found that while electron-poor salts are highly efficient, electron-rich ones tend to suppress the reaction. To investigate reasons of such reactivity difference between poor and rich salts DFT calculations were done, which shed light on mechanisms for both types of salts. After that we focused on addressing the mentioned challenge and developed another catalytic system enabling less reactive electron-rich salts to participate in the reaction. Also, it was shown that highly substituted aryl germanes are effective cores for complex molecules synthesized in modular fashion.The second chapter describes conversion of C-Ge into C-O and C-N bonds. The former consists in development of a mild, ligand-free and fast coupling between aryl germanes and alcohols based on Pd(II)/Pd(IV)-catalysis. Using simple Pd-source, Pd(OAc)2, and PIFA as oxidant the transformation provides a coupling with primary, secondary and tertiary alcohols and demonstrates exclusive selectivity towards germanes tolerating all other types of reactive motifs, such as Bpin, SiMe3 and especially halogens, which are typical reagents in C-O coupling. Moreover, carboxylic acids were introduced as well effectively producing the corresponding aryl esters. Furthermore, we successfully demonstrated orthogonal behavior of aryl germanes in a number of typical C-O bond formation reactions, namely Cu-, Pd- and Ni-reactions. In all mentioned reactions germane fully untouched letting other functionalities to undergo the transformation. Also, though 10 mol
%F PUB:(DE-HGF)11
%9 Dissertation / PhD Thesis
%R 10.18154/RWTH-2025-01329
%U https://publications.rwth-aachen.de/record/1004271