A02 • Boron-Based Super Electron Donors for Transition-Metal-Free Radical Borylation

Transition-metal-free borylations are attracting increased attention, as these processes are environmentally benign and green alternatives to commonly transition-metal-(TM)-catalyzed borylation processes. Such processes provide many advantages such as lower costs, the avoidance of heavy metal usage and heavy metal contamination in the final product. Super electron donors (SEDs) have gained attention due to their numerous advantages over traditional metallic reducing agents, such as low toxicity, good solubility in organic solvents, mild reaction conditions, tunable reduction capabilities, and often excellent chemoselectivity. SEDs are often used to induce radical reactions, but their application in borylation reactions, especially in catalytic variants, is still underdeveloped. The aim of this project is to achieve transition-metal-free, SED-catalyzed borylation of various organic substrates through radical reaction mechanisms and to explore the scope and mechanistic details of such processes by combining quantum-chemical calculations with experimental methods, thereby gaining a deep, fundamental knowledge of this type of chemistry. The main research questions to be explored in this project using experimental (Ye group) as well as quantum chemical (Holthausen group) methods are: (i) the correlation between boron-SED reduction capability and molecular structure; (ii) the scope of substrates and boryl sources; (iii) the mechanism of boron-SED catalyzed borylations. During the first funding period of the collaborative research center, a toolkit of boron based SEDs will be synthesized and fully characterized. Their reducing properties and their potential as catalysts for the borylation of aryl and alkyl halides will be assessed. The underlying reaction mechanisms will be investigated.