Effective Heterogeneous Catalyst for Suzuki-Miyaura Cross-Coupling in Aqueous Media : Melamine Cyanurate Complex Containing Pd Species

A melamine cyanurate complex catalyst containing Pd(II) ions (denoted Pd/M-CA) was effective for Suzuki-Miyaura cross-coupling reactions in environmentally benign aqueous media at room temperature. The reaction conditions, such as the type of Pd species in Pd/M-CA, loading amounts of Pd, solvent, and substrate concentration, were investigated for optimization. In the presence of Pd/M-CA under the optimal conditions, cross-coupling reactions of a wide range of structurally diverse aryl halides and arylboronic acids containing functional groups proceeded smoothly to provide the corresponding products in high yields. In addition, the Pd/M-CA could be reused at least 5 times while maintaining high yields. The reduction of Pd(II) ions in Pd/M-CA to Pd(0) by NaBH4 enhanced the catalytic activity to provide a high turnover number (TON) of 17600 and turnover frequency (TOF) of 880 h−1.