Photochemical reactions of acylsilanes towards the construction of carbon-carbon bonds

Abstract

Photochemistry is a field of chemistry which has fascinated chemists for centuries. The access to the photoexcited state of molecules allows otherwise unattainable reactivity and access to completely novel structures. The use of light as a reagent in organic synthesis can also circumvent the need of toxic or expensive reagents commonly used in traditional synthetic chemistry, making photochemistry an attractive tool in the context of Green Chemistry. Acylsilanes are a class of compounds with rich photochemistry. They possess the unique ability to undergo photorearrangement to reactive nucleophilic siloxycarbenes. While this metal-free method for carbene generation is highly promising, the number of known efficient reactions they undergo is limited and underexplored. In this thesis, a variety of acylsilanes have been synthesized in order to further explore and expand their known photo reactivity and obtain new complex structures via C-C bound forming photoreactions. A regioselective intramolecular [2+2]-photocycloaddition of benzoyl(allyl)silanes was developed to yield novel silacyclopentanes, compounds that may be used as silicon bioisosteres of cyclopentanes. Additionally, a novel formal (4+1)-cycloaddition of photogenerated siloxycarbene with electrophilic dienes was discovered, allowing the synthesis of highly functionalized cyclopentenes and expanding the limited reactivity of such carbenes with olefins. During the synthesis of acylsilanes via the dithiane umpolung methodology an autooxidative condensation of lithiated aryl dithianes was serendipitously uncovered, which yielded complex α-thioether ketone orthothioesters, some of which present strong cytotoxic activity against glioblastoma cancer cell lines.