Anchoring palladium acetate onto imine-functionalized silica gel through coordinative attachment: An effective recyclable catalyst for the Suzuki-Miyaura reaction in aqueous-isopropanol

Silica supported palladium catalyst, Pd@imine-SiO2, was prepared by immobilizing Pd(OAc)(2) onto silica gel through coordination of imine, generated via Schiff-base condensation between 3-aminopropyltriethoxysilane (APTES) functionalized silica gel and acetamide. The catalyst was characterized by FTIR, BET surface area measurements, XRD, SEM-EDX and ICP-AES. The imine-based catalyst, exhibited excellent activity for the Suzuki-Miyaura cross-coupling reactions of aryl halides with arylboronic acids in iPrOH/H2O (1: 1) under mild conditions (T = 60 degrees C, air, 0.08 mol% of palladium). Interestingly, under the same experimental conditions, for the reaction between p-bromoanisole and phenylboronic acid the imine-based catalyst, Pd@imine-SiO2, exhibited comparable result with that of homogeneous Pd(OAc)(2) and much higher activity than amine-based catalyst, Pd@APTES-SiO2. Furthermore, the imine-based catalyst could be recovered by simple filtration and reused several times without significant loss of activity. (C) 2012 Elsevier B.V. All rights reserved.