Palladium-Catalyzed Suzuki Reactions in Water with No Added Ligand: Effects of Reaction Scale, Temperature, pH of Aqueous Phase, and Substrate Structure

Abstract

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.

Effective BI‐DIME Ligand for Suzuki–Miyaura Cross‐Coupling Reactions in Water with 500 ppm Palladium Loading and Triton X

“…Previously, it had been reported for SMC reactions that there was a relationship between the change in pH value during the reaction and product yield . The impact of the number of equivalents of K 3 PO 4 base was also studied for this catalytic system (with 500 ppm Pd/ 6 precatalyst solution), and we observed that the rate of the reaction was at least three‐fold faster with 1.2 equivalents of K 3 PO 4 (initial pH value: 10.5, final pH value: 7.5) than with 2 equivalents of K 3 PO 4 (initial pH value: 12, final pH value: 10; Figure , curves a and b).…”

Lewis Acid Catalyzed Regio- and Diastereoselective Synthesis of Spiroisoxazolines via One-Pot Sequential Knoevenagel Condensation/1,3-Dipolar Cycloaddition Reaction

“…It was found that the ligand 14b resulted the higher isolated yield and in the absence of any ligands products 16a and 17 were obtained in 68% and 33% isolated yield, respectively (Scheme 4). 15 The ligand 14b was tested in copper-catalyzed homocoupling of 4-methoxyphenylbronic acid (15b) and the desired 4,4′-dimethoxy-1,1′-biphenyl (16b) was obtained in 90% isolated yield. It is notable that in the absence of ligand 14b, the product 16b was obtained in <14% isolated yield (Scheme 4).…”

Palladium‐catalysed room‐temperature Suzuki–Miyaura coupling in water extract of pomegranate ash, a bio‐derived sustainable and renewable medium

“…Even though several hundreds of studies have appeared in the literature, it remains unanswered, even for a simple case, which procedure or catalyst is the best one . On the other hand, several new methodologies have still appeared using several modified conditions including ligands, catalysts, solvent, additives, etc . In this connection and in continuation of our recent research on the development of benign methodologies for C–C coupling, we report here an effective method for SMC using a natural feedstock, water extract of pomegranate ash (WEPA), as a green and sustainable (basic) medium.…”

“…Palladium catalysts with appropriate ligands and bases in organic or biphasic media assist as common systems for SMC reactions . The frequently employed ligands for this purpose include phosphines, palladacycles, sterically crowded N ‐heterocyclic carbenes, imines and oximes .…”