Acylsilane in Übergangsmetall-katalysierten C-H-Funktionalisierungen und Anwendungen von Siloxycarbenen in synthetischer Chemie

The insertion of carbenes into C–H bonds and the addition of carbenes to unsaturated C–C bonds are direct approaches towards the formation of new C–C bonds. However, the current methods for accessing reactive carbenes are limited, and these transformations predominantly utilize diazocarbonyl compounds. Acylsilanes are known to undergo 1,2-silicon-to-oxygen migration (Brook rearrangement) under thermal or photochemical conditions to form siloxycarbenes. Although the generation of such intermediates is preparative simple and their application in C–C bond forming processes appears synthetically attractive, only a limited number of reports regarding the utilization of siloxycarbenes have been published. By establishing new methods for the synthetic utilization of siloxycarbenes, current synthetic strategies were extended and complex products were obtained under mainly very mild photochemical conditions. Our group developed the intramolecular silylacylation reaction of alkynes. In this process, siloxycarbenes add to the alkyne under photochemical conditions to yield highly functionalized chromanone derivatives in high selectivities. In this thesis, the silylacylation reaction was applied to the intermolecular reaction process. Aromatic acylsilanes were converted with electron-deficient alkynes under visible light irradiation to yield silyl vinyl ketones in moderate to high yields and good selectivities. The reaction of siloxycarbenes with alkenes remained virtually unexplored. To facilitate a study of this reaction, aromatic ortho-olefinated acylsilanes were prepared by a rhodium-catalyzed oxidative C–H bond functionalization process involving the application of the acylsilane moiety as a directing group. When exposed to visible-light irradiation, the ortho-olefinated aromatic acylsilanes underwent a smooth intramolecular cyclization process to afford valuable indene derivatives in quantitative yields. In literature, only a few protocols involving siloxycarbenes for the synthesis of oxygen- or sulfur-containing heterocycles have been reported. However, no application for the synthesis of N-heterocyclic compounds was reported to date. We developed a synthetic pathway to ortho-amidated aromatic acylsilanes by using an iridium-catalyst in the presence of sulfonyl azides. When modifying the amide-functionality, model substrates were obtained by introducing reactive side chains. By exposing to visible-light or thermal irradiation, the model compounds underwent smooth intramolecular cyclization processes affording a variety of N-heterocyclic products (e.g. indols or dihydroquinolinones) in up to quantitative yields