Photochemical Translocation of Alkenes and Alkynes by Catalytic C(sp3)–H Sampling

• Applicant: Dr. Simon Kolb
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 554816749

The translocation of functional groups has emerged as a promising variant to functionalize positions in molecules that are hard to address. Most of the reported strategies in this field run through radical mechanisms that require the molecule to have a molecular handle (e.g. terminal olefins) that can react with the extrinsic radicals to initiate the migration process. Endeavors in this field have already led to the translocation of alkenes, alkynes, nitriles, carbonyls or heteroarenes. To avoid the need of extrinsic radicals, photochemical activation of a hydrogen atom transfer catalyst allows the generation of radicals by direct C(sp3)–H abstraction leading to the same mechanistic key intermediates for translocation. Given the fact that this strategy allows migration by isomerization and does not require additional functionality to be installed, it is considered superior to extrinsic strategies; however, the migration by direct C(sp3)–H is also highly underexplored. Herein it is proposed to develop a photochemical protocol that allows the transposition of alkenes and alkynes by catalytic C(sp3)–H sampling. Sampling should be achieved by utilizing catalytic amounts of a hydrogen atom abstractor and a hydrogen atom donor which create a dynamic system that allows radical formation by taking bond-dissociation energies, polarity and the steric environment of the abstracted hydrogen atom to be extracted into account. In case multiple hydrogen atoms show similar properties for abstraction, kinetic preference for cyclization to a key intermediate guides which carbon atom the functional group will be migrated to. It is planned to explore translocations in acyclic and cyclic systems, but also to develop ring-expansion and ring-contraction chemistry. The strategies will be applied to real-word examples and utilized for shortcuts to challenging targets that require multi-step synthesis. Downstream reactions of alkynes and alkenes will be showcased to highlight the benefits of transposition of these groups.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professorin Alison Wendlandt, Ph.D.