Photocatalytic Cascade Cyclization of Aryl Haloalkynyl Ketones Forming Cyclopenta[]naphthalene Derivatives.

An efficient metal-free, photoredox-mediated cascade cyclization of aryl 1-haloalk-5-ynyl ketones has been developed. Using catalytic amounts of eosin Y (EY) and EtNMe as a reductive quencher, various aryl 1-haloalk-5-ynyl ketones have been transformed into the corresponding cyclization products in up to 98% yield. As a result, synthetic access to differently α-functionalized cyclopenta[]naphthones and direct construction of cyclopenta[]naphtholes has been developed.