Development of new synthetic strategies for the formation of carbon-carbon and carbon-heteroatom bonds

Jana, Sripati; Königs, René Michael (Thesis advisor); Patureau, Frédéric W. (Thesis advisor)

Aachen : RWTH Aachen University (2022)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2022

Abstract

This thesis is dedicated to the development of new synthetic strategies for the construction of new carbon-carbon and carbon-heteroatom bonds by using different aspects of carbene transfer reactions and photoinduced transition-metal catalyzed C-H functionalization reactions. The second chapter of this thesis describes Rh(II)-catalyzed sigmatropic rearrangements of organoselenium compounds with aryl diazoacetates. Depending on the substitution patterns of the selenium compounds, the corresponding selenium ylide intermediates undergo a variety of sigmatropic rearrangements, such as the Doyle-Kirmse rearrangement, Sommelet-Hauser rearrangement, and Stevens rearrangement reactions to furnish densely functionalized organoselenium compounds. This methodology offers the simultaneous formation of C-C and C-Se bonds. Moreover, the Doyle-Kirmse rearrangement reactions of difluoroacetate substituted allyl sulfide are also described. This protocol provides straightforward access to a range of valuable fluorinated homoallylic thioethers under mild reaction conditions. The third chapter of this thesis demonstrates the Au(I)-catalyzed site-selective C-H functionalization reactions of unprotected and protected N-heterocycles such as carbazoles, phenothiazines, and phenoxazines, under mild and ambient reaction conditions. Moreover, the efficiency of this methodology is further underlined by utilizing this protocol in multi C-H functionalization reactions and could showcase up to six-fold C-H functionalizations of a molecule with multiple carbazole units. The fourth chapter of this thesis describes photochemical carbene transfer reactions of various carbene precursors. A wide variety of classic bench-marked organic transformations such as sigmatropic rearrangements, C-H functionalizations, cycloadditions, and cascade reactions are investigated under mild and metal-free reaction conditions. This protocol provides an environmentally benign alternative to the transition metal-catalyzed carbene transfer reactions. In the fifth chapter, an unprecedented photoinduced proton transfer strategy is documented to realize the functionalization of unreactive alcohols for the formation of new C-O bonds. Finally, the recently emerging concept of metallaphotoredox catalysis is utilized to functionalize the unreactive C(sp3)-H bond of pyridyl substituted amides for the construction of synthetically challenging new C-C bonds, which is inaccessible under classic thermal reaction conditions.

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