Synthesis of 2-Fluorobenzofuran by Photocatalytic Defluorinative Coupling and 5-endo-trig Cyclization

An alkyl radical-triggered dual C-F bond cleavage of alpha-CF3-ortho-hydroxystyrenes for the synthesis of 2-fluorobenzo-furans was developed. The visible-light-induced defluorinative cross-coupling reactions of alpha-CF3-ortho-hydroxystyrenes with a variety of carboxylic acids produced gem-difluoroalkenes, which underwent SNV-type 5-endo-trig cyclization to give 2-fluorobenzo-furans. Mechanistic studies indicated that the electron transfer between phenoxyl radicals and carboxylates was the major pathway for the generation of alkyl radicals.

Automated summary

A dual C-F bond cleavage of alpha-CF3-ortho-hydroxystyrenes triggered by alkyl radicals was developed for the synthesis of 2-fluorobenzo-furans. The visible-light-induced defluorinative cross-coupling reactions of alpha-CF3-ortho-hydroxystyrenes with various carboxylic acids produced gem-difluoroalkenes, which underwent SNV-type 5-endo-trig cyclization to give 2-fluorobenzo-furans. Mechanistic studies revealed that electron transfer between phenoxyl radicals and carboxylates was the main pathway for alkyl radical generation.