Sonogashira-Hagihara Coupling towards Diaryl Alkynes Catalyzed by FeCl3•6?H2O/Cationic 2,2'-Bipyridyl

Efficient and environmentally benign one-pot SonogashiraHagihara coupling of aryl iodides with 4-aryl-2-methylbut-3-yn-2-ols catalyzed by an FeCl3 center dot 6?H2O/cationic 2,2'-bipyridyl system in water under air in the presence of zinc powder reductant was performed. Various aryl iodides and 4-aryl-2-methylbut-3-yn-2-ols were used as reactants, which afforded moderate to high yields of cross-coupled products. Although alkyl-substituted 2-methylbut-3-yn-2-ol could not be coupled with aryl iodides, the use of alkyl terminal alkynes under similar conditions provided the corresponding products in moderate yields. This reaction protocol was also used to synthesize both symmetric and asymmetric 1,4-diarylbuta-1,3-diynes. This one-pot iron-catalyzed SonogashiraHagihara coupling reaction progressed without the use of an organic solvent, a copper cocatalyst, or an inert atmosphere, rendering it an environmentally friendly method with potential for practical applications.