Solventless Suzuki coupling reaction

Kabalka, G.W., Wang, L., Pagni, R.M., Hair, C.M. and Namboodiri, V., Solventless Suzuki coupling reactions on palladium-doped potassium fluoride alumina, Synthesis, 2003, 217-222. 

A solventless Suzuki coupling reaction has been developed using both thermal and microwave-assisted methods. A potassium fluoride-alumina mixture is utilized along with palladium powder. The KF acts as a base. ... 

A rapid MW-assisted palladium-catalyzed coupling of heteroaryl and aryl boronic acids with iodo- and bromo-substituted benzoic acids, anchored on TentaGel has been achieved [174]. An environmentally friendly Suzuki cross-coupling reaction has been developed that uses polyethylene glycol (PEG) as the reaction medium and palladium chloride as a catalyst [175]. A solventless Suzuki coupling has also been reported on palladium-doped alumina in the presence of potassium fluoride as a base [176], This approach has been extended to Sonogashira coupling reaction wherein terminal alkynes couple readily with aryl or alkenyl iodides on palladium-doped alumina in the presence of triphenylphosphine and cuprous iodide (Scheme 6.52) [177]. 

The development of a solventless, microwave-assisted Suzuki reaction utilizing a readily recyclable solid catalyst offers numerous benefits. These include the straightforward recovery of both product and catalyst, conservation of energy through the use of microwave irradiation, simple commercial scale up, and low waste protocols due to the absence of solvents. Recently, Kabalka et al. reported such a procedure for the reaction between aryl iodides and arylboronic acids or vinyl boronic adds in the presence of KF-AI2O3 as a base [75a] to provide excellent yields of expected coupled products (Equation 87) [75b],... 

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