Microwave-assisted aqueous Suzuki cross-coupling reactions

The poly(ethylene glycol) ester of bromo-, iodo-, and triflate-para-substit uted benzoates are smoothly cross-coupled with aryl boronic acids (Suzuki r eaction) under "ligandless" palladium acetate catalysis in water. The react ion proceeds without organic cosolvent under conventional thermal condition s (70 degrees C, 2 h) and under microwave irradiation (75 W, 2-4 min). The polymeric support remains stable under both reaction conditions. Whereas co nventional thermal conditions induced ester cleavage (up to 45%), this side reaction is suppressed when microwave conditions are employed. Aryl nonafl ates give fair yields under these conditions. Non-polymer-bound aryl halide s form biaryls in good to excellent yields in water/poly(ethylene glycol) m ixtures under microwave irradiation (4 min, 75 W).