Visible‐Light‐Mediated Synthesis of β‐Chloro Ketones from Aryl Cyclopropanes

We report the visible‐light‐mediated synthesis of β‐chloro ketones from aryl cyclopropanes, oxygen, hydrochloric acid, and nitric acid. The operationally simple and catalyst‐free method uses cheap standard laboratory reagents and displays broad functional‐group tolerance. Moreover, scale up of the reaction and late‐stage functionalization of bioactive compounds is possible, providing the opportunity to utilize the cyclopropane ring as a masked β‐chloro ketone in a reaction sequence. We propose a light‐driven radical chain reaction initiated by the reaction of diluted hydrochloric and nitric acid to produce small quantities of molecular chlorine. The mechanistic hypothesis is supported by ¹⁸O labelling and UV/Vis experiments, cyclovoltammetry, and several control reactions.