Photoredox Functionalization of 3-Halogenchromones, 3-Formylchromones, and Chromone-3-carboxylic Acids: Routes to 3-Acylchromones.

This work describes a set of new and efficient synthetic routes toward 3-acyl-substituted chromones ranging from readily available chromone precursors, namely 3-halogenchromones, 3-formylchromones, and chromone-3-carboxylic acids by means of visible-light photoredox catalysis. The operationally simple protocols transform a wide variety of chromone derivatives into challenging 3-acyl-substituted chromones in excellent yield. This research also aimed at comparing the developed methodologies by using as the key evaluation criteria the efficiency of the reaction and general availability of the starting materials. The application of all developed methods for the gram-scale preparation of the title chromones was also demonstrated.