Visible Light-Induced Regioselective Intermolecular [2 + 2]-Cycloaddition of Alkyne and 2(1H)‑Quinolone Derivatives

We have developed a visible light-induced intermolecular [2 + 2]-cycloaddition reaction between alkenes and alkynes using thioxanthone and Cu­(OTf)₂ as cocatalysts. Various quinolin-2­(1H)-ones, featuring diverse substituted groups, were successfully employed in this reaction, resulting in the synthesis of a series of 4,8b-dihydrocyclobuta­[c]­quinolin-3­(2aH)-ones. Our methodology presents a novel synthetic approach for alkene-alkyne [2 + 2]-cycloaddition, delivering cyclobutene derivatives with exceptional regioselectivity.