Photochemical Thioester Transfer to Alkynes via Selective Hydrothiocarbonylation

We report the first hydrothiocarbonylation of (un)activated alkynes using bench-stable 1,4-DHP thioester surrogates under photochemical conditions, enabling a general route to (<i>E</i>)-α,β-unsaturated thioesters with excellent regio- and stereoselectivity. A Pd/photoredox catalytic system facilitates DHP thioester activation and site-selective hydrocarbonylation while controlling photoisomerization and side reactions. Moreover, a combination of benzil and boron Lewis acid pairs promotes <i>E</i>-to-<i>Z</i> photoisomerization, accessing (<i>Z</i>)-α,β-unsaturated thioester.