Visible‐Light‐Assisted Cobalt‐2‐(hydroxyimino)‐1‐phenylpropan‐1‐one Complex Catalyzed Pd/Cu‐Free Sonogashira–Hagihara Cross‐Coupling Reaction

Abstract An effective and inexpensive strategy for the Co(C 9 H 9 NO 2 ) 3 catalyzed Sonogashira–Hagihara cross‐coupling reaction of aryl bromides containing electron‐rich and electron‐poor substituents with terminal alkynes was demonstrated. The reaction proceeded smoothly in the presence of ethylene glycol as additive and K 2 CO 3 as base in DMF under visible light illumination, and 23 alkyne products were afforded in moderate to excellent yields, including four new diaryl ethynes. Compared with the high‐cost palladium catalyst, cobalt is an inexpensive catalyst with a preponderance of technologized production, and the palladium/copper‐free catalytic system not only provided an efficient process with mild reaction conditions, but also enhanced the substrate group tolerance.