Direct Introduction of an Acetyl Group at the α‐Carbon Atom of an Arene Ring through an Amide Photo‐Fries Rearrangement upon Exposure to UV Light

We employed an amide photo‐Fries rearrangement for the synthesis benzoheterocyclic compounds and found that direct acylation of the α‐carbon atom in an arene ring can occur upon exposure to ultraviolet (UV) light. In this reaction, the N‐acetyl group of amides underwent rearrangement to the α‐position across the bridgehead carbon atom under UV−C light. The reaction conditions were gentle and safe. Moreover, this reaction proves to be more convenient for selectively manipulating benzoheterocyclic compounds in comparison to traditional approaches involving Lewis acid catalysts or anionic reagents. Photo‐Fries rearrangement using benzoheterocyclic compounds, which are widely used in pharmaceuticals, was studied. Under ultraviolet (UV) light, benzoheterocyclic compounds containing an N‐acetyl group underwent rearrangement of the acyl group directly to the α‐position past the adjacent bridgehead carbon. This environmentally friendly method could be useful in organic synthesis, the pharmaceutical industry, and biochemistry.