Photocatalytic Synthesis of Stilbenes via Cross‐Coupling of Alkenyl Boronic Acids and Arenediazonium Tetrafluoroborate Salts

Abstract In this article, we describe the development of a new method for the photocatalytic synthesis of ( E )‐stilbenes by the coupling of alkenyl boronic acids and aryldiazonium salts. In our operatively simple and metal‐free system, visible light is used as an energy source and a “green” mixture of water and ethanol is used as solvent. A mechanistic explanation is presented which is supported by several control experiments. The reaction proceeds via a radical pathway, from both the diazonium salt and boronic acid in the presence of visible light.