Photoredox α‐Allylation of α‐Halocarbonyls with Allylboron Compounds Accelerated by Fluoride Salts under Visible Light Irradiation

Abstract Organic dyes are an attractive alternative to the use of transition‐metal complexes in photoredox catalysis. Herein, we report an inexpensive organic dye (eosin Y)‐catalyzed radical coupling of α‐bromocarbonyl compounds with allyltrifluoroborates under visible light irradiation. This reaction was accelerated by either Bu 4 NF or CsF. Based on mechanistic studies, the cation exchange between potassium allyltrifluoroborate and Bu 4 NF proceeded to generate KF. The generated KF or CsF acts as a Lewis acid to promote a single electron transfer (SET) from eosin Y to α‐halocarbonyls. The protocol was applied to bromoesters, bromoketones, and bromoamides to give the coupling products in high yields.