The heterogeneous palladium-catalyzed Suzuki reactions between model aryl bromides (4-bromoanisole, 4-bromoaniline, 4-amino-2-bromopyridine, and 2-bromopyridine) and phenylboronic acid have been successfully conducted in water with no added ligand at the 100-mL scale using 20-40 millimoles of aryl bromide. The product yields associated with these substrates were optimized and key reaction parameters affecting the yields were identified. The results clearly indicate that the reaction parameters necessary to achieve high yields are substrate dependent. In addition, it is demonstrated that aqueous Suzuki reactions of substrates containing basic nitrogen centers can produce quantitative yields of desired products in the absence of added ligand.KEYWORDS: palladium catalysis without added ligand, Suzuki reactions in water, heterogeneous catalysis, scale-up, green and sustainable Suzuki reactions.
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