Photoinduced Specific Acylation of Phenolic Hydroxy Groups with Aldehydes.

A convenient method is reported to specifically acylate phenolic hydroxyl groups through a radical pathway. When a mixture of an aldehyde and a phenol in ethyl acetate is irradiated with blue light in the presence of iridium and nickel bromide catalysts at ambient temperature, phenoxyl and acyl radicals are transiently generated in situ and cross-couple to furnish an ester. Aliphatic hydroxy groups remain untouched under the reaction conditions.