Oxidant and Transition-Metal-Free Photoinduced Direct Oxidative Annulation of 1‑Aryl-2-(furan/thiophen-2-yl)butane-1,3-diones

A photoinduced direct oxidative annulation of 1-aryl-2-(furan/thiophen-2-yl)­butane-1,3-diones and ethyl-2-(furan-2-yl)-3-oxo-3-(aryl-2-yl)­propanoates in EtOH without the need for any transition metals and oxidants provided access to highly functionalized polyheterocyclic 1-(5-hydroxynaphtho­[2,1-b]­furan-4-yl)­ethanones and 1-(5-hydroxyfuran/thieno/pyrrolo­[3,2-e]­benzofuran-4-yl)­ethanones. The phenomenon of excited-state intramolecular proton transfer (ESIPT) was observed for both 1-(5-hydroxynaphtho­[2,1-b]­furan-4-yl)­ethanone and 1-(5-hydroxy furan/thieno/pyrrolo­[3,2-e]­benzofuran-4-yl)­ethanone analogues.