h1

%0 Thesis
%A Pei, Chao
%T Theoretical mechanistic investigations of carbene and nitrene transfer reactions
%I RWTH Aachen University
%V Dissertation
%C Aachen
%M RWTH-2022-10534
%P 1 Online-Ressource : Illustrationen, Diagramme
%D 2022
%Z Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2023
%Z Dissertation, RWTH Aachen University, 2022
%X My PhD thesis focuses on the study of transition-metal catalyzed or photochemical carbene and nitrene transfer reactions. Firstly, detailed computational studies revealed that electrophilic gold(I)-carbene prefers a site-selective C−H functionalization of carbazole, in which trace amounts of water play a crucial role to rationalize the selectivity. Secondly, gem-difluoro olefinations of electron-rich anilines with trifluoromethyl diazoalkanes under copper(I) catalysis were investigated by DFT calculations. It indicated that anilines play a dual role in this reaction - stabilizing the zwitterion intermediate and promoting the deprotonation process. In addition, trifluoromethyl diazoalkanes could be utilized in Pd-catalyzed cross couplings with vinyl bromides, leading to synthetically challenging trifluoromethylated tetrasubstituted allenes. Moreover, theoretical investigations uncovered the potential mechanisms of several Rh(II)-catalyzed 1,3-difunctionalization reactions of triazoles with selenides or sulfides.Instead of metal catalysis, the emerging photochemical carbene transfer reactions opened up several unsolved mechanism questions. Firstly, under blue light irradiation, the spin states of photochemically generated diaryl carbenes are controlled by substituents on the aryl rings, which results in divergent reactivity such as cyclopropenations, C(sp)−H insertion, or cascade cyclization reactions with alkynes. Moreover, computational study indicated that photoinduced O-H insertion reactions of diaryl diazomethanes or aryl diazoacetates involve hydrogen-bond-assisted intersystem crossing processes. In addition, calculations supported the formation of an oxonium ylide in three-component reaction with N-fluoro-benzenesulfonimide (NFSI), aryl diazoacetates and 1,4-dioxane. In the last section, our theoretical studies revealed that the photosensitizer-promoted decomposition of ethyl diazoacetate (EDA) opens up its radical or triplet reactivity, which were successfully applied in gem-difluoroolefinations reactions. In the next part, we conducted theoretical studies on photochemical formal C−H aminations of α-methyl styrene with iminoiodinane via triplet nitrene intermediates, and nitrene radical anion reactivity in aziridinations of styrenes under photoredox catalysis.Last but not least, detailed calculations were performed on novel Ru(II)-catalyzed C(sp3)−C(sp3) coupling reactions of methylpyridyl-substituted amides and alkyl bromides. We identify that cyclometalated metal-substrate-bound complexes can be regarded as a photosensitizer, which promote further intramolecular single electron transfer (ISET) processes and C(sp3)−C(sp3) diradical couplings. In addition, photoinduced palladium catalysis has also been applied in the radical transformations, such as the cascade radical cyclization of isonitriles, which afforded phenanthridines in high efficiency.
%F PUB:(DE-HGF)11
%9 Dissertation / PhD Thesis
%R 10.18154/RWTH-2022-10534
%U https://publications.rwth-aachen.de/record/855909