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 °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.

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► Silica-supported Pd-catalyst developed for the Suzuki–Miyaura reaction.
► Aqueous-isopropanol could be used as solvent.
► The catalyst could be recycled up to six times without loss in activity.
► Imine-based catalyst is more effective than amine-based catalyst.
► Comparable activity has been obtained with that of homogeneous palladium acetate.