Light-driven metal-free thiocarbonyl – olefin metathesis: a general route to sterically hindered alkenes
Year: 2026
Type: preprint
Abstract: Highly substituted olefins are attractive scaffolds for molecular machines, optical materials and medicinal chemistry, whilst also serving as valuable intermediates in organic synthesis. However, their efficient and general preparation remains challenging, particularly in light of sustainability requirements. Here, we report a metal-free photochemical thiocarbonyl – olefin metathesis that provides access to a broad range of tri- and tetra-substituted alkenes, where light irradiation promotes both the regioselective formation and subsequent fragmentation of thietane intermediates. The scarcely explored photochemical cycloreversion of isolated thietanes was first thoroughly reinvestigated, leading to the proposal of a thioparabanate-photocatalyzed mechanism supported by Time-Dependent Density Functional Theory (TD-DFT) calculations. Then, the combination of this cycloreversion with a thia-Paternò_Büchi reaction into a photochemical cascade, enables the in situ generation of the thietane intermediate. Starting from thiocarbonyl substrates, independently prepared or generated in situ via Norrish type II fragmentation of phenacyl sulfide precursors, and diverse alkene partners, this light-mediated thiocarbonyl – olefin coupling offers an innovative and sustainable entry to a library of densely substituted olefins. The synthetic utility of this strategy is also demonstrated through its application to molecular motor templates synthesis.
Source: ChemRxiv
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221828190