Bam, RadhaPollatos, Alexandros S.Moser, Austin J.West, Julian G.2021-03-092021-03-092021Bam, Radha, Pollatos, Alexandros S., Moser, Austin J., et al.. "Mild olefin formation via bio-inspired vitamin B12 photocatalysis." <i>Chemical Science,</i> 12, no. 5 (2021) Royal Society of Chemistry: 1736-1744. https://doi.org/10.1039/D0SC05925K.https://hdl.handle.net/1911/110158Dehydrohalogenation, or elimination of hydrogen-halide equivalents, remains one of the simplest methods for the installation of the biologically-important olefin functionality. However, this transformation often requires harsh, strongly-basic conditions, rare noble metals, or both, limiting its applicability in the synthesis of complex molecules. Nature has pursued a complementary approach in the novel vitamin B12-dependent photoreceptor CarH, where photolysis of a cobalt–carbon bond leads to selective olefin formation under mild, physiologically-relevant conditions. Herein we report a light-driven B12-based catalytic system that leverages this reactivity to convert alkyl electrophiles to olefins under incredibly mild conditions using only earth abundant elements. Further, this process exhibits a high level of regioselectivity, producing terminal olefins in moderate to excellent yield and exceptional selectivity. Finally, we are able to access a hitherto-unknown transformation, remote elimination, using two cobalt catalysts in tandem to produce subterminal olefins with excellent regioselectivity. Together, we show vitamin B12 to be a powerful platform for developing mild olefin-forming reactions.engThis Open Access Article is licensed under a Creative Commons Attribution 3.0 Unported LicenceJournal articled0sc05925khttps://doi.org/10.1039/D0SC05925K