Metal complexes that contain carbohydrate-substituent (Carb-) N-heterocyclic carbenes (NHCs) ligand have demonstrated great success as catalysts for organic synthesis reactions. In this study, four new Carb-NHC-Pd complexes 2a-d were prepared and their catalytic activities for Suzuki-Miyaura reaction were evaluated. The Carb-NHC-Pd complex behaved as a general surfactant which leads to the formation of a temporary oil-in-water contact interface, thereby promoting the Suzuki-Miyaura reaction. A long hydrophobic alkyl chain (-nC16H33) was remotely linked to complex 2d, in which Carb-NHCs showed high electron-donating properties, and steric bulk with 1JCH constant of 1H NMR. Complex 2d exhibited a higher catalytic activity as compared with 2a (-nC2H5), 2b (-nC4H9), and 2c (-nC8H17). A series of fluorene-cored materials with different aryl groups were synthesized with high yields (34 examples, 91-99%) under the optimized reaction conditions.
Keywords: Aqueous Suzuki–Miyaura reaction; Carbohydrate; N-heterocyclic carbenes; PEPPSI styled Precatalysts; Palladium.
Copyright © 2022. Published by Elsevier Ltd.