Palladium-promoted reaction Sonogashira

Erdelyi, M., Gogoll, A. Rapid Microwave Promoted Sonogashira Coupling Reactions on Solid Phase. J. Org. Chem. 2003, 68, 6431-6434. Najera, C., Gil-Molto, J., Karlstroem, S., Falvello, L. R. Di-2-pyridylmethylamine-Based Palladium Complexes as New Catalysts for Heck, Suzuki, and Sonogashira Reactions in Organic and Aqueous Solvents. Org. Lett. 2003, 5,1451-1454. 

It was also found that the Sonogashira reaction [69] takes place under aqueous alkaline conditions in the presence of the PS-PEG-supported palladium complex 59 [95]. The combination of the resin catalyst 59, cesium hydroxide [96], and water is essential to promote high yielding coupling of 69. Using copper-free conditions, a one-step preparation of the benzofurans 70 was achieved in water via coupling of 2-iodophenol 68 (X=OH) and the terminal alkynes (Scheme 23). 

Reisch and Nordhaus observed a related furan formation to produce a small amount of 85 (0 to 49%) in the Sonogashira coupling of 3-iodoquinolinone derivatives 83 in some cases (Scheme 19.18) [28]. They confirmed that furan formation proceeds from a coupling product 84 [R = C(Et)(Me)OH] in the presence of CuI/EtsN without using the palladium catalyst. This result demonstrated that cyclization is promoted by copper salts. A highly related catalytic reaction using Cul (5 mol %) in EtOH/EtsN was also reported [29]. 

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