凯发

Synergistic catalysis is a synthetic strategy wherein both the nucleophile and the electrophile aresimultaneously activated by two separate and distinct catalysts to afford a single chemicaltransformation[1]. This powerful catalysis strategy can not onlyintroduce previously unattainable chemical transformations, but also improve the catalytic efficiencyof existing transformations. Herein, we demonstrated a facile strategy of merging an organic amine with palladium complex on graphene oxide (GO) as a synergeticand recyclable catalyst for Tsuji-Trost allylation coupling. Through silylation modification with [3-(diethylamino) propyl] trimethoxysilane  and 3-(2-aminoethylamino) propyl trimethoxysilane, followed by a coordination process, a tertiary amine and palladium-diamine complex were simultaneously immobilized onto the GO support (GO–NEt2–2N–Pd)[2]. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) mapping and transmission electron microscopy (TEM) confirm the successful preparation of the designed catalyst. Systematic investigation revealed the palladium-diamine complex was effective for Tsuji-Trost allylation of allyl methyl carbonate with ethyl acetoacetate, resulting in a 44.52% yield in 5 h. When the tertiary amine was introduced, the conversion reached up to 91.85% within the same time, with a yield of 87.67% and 4.18% for the monoallylation and diallylation product, respectively, revealing the obvious promotion effect of the introduced tertiary amine. The catalyst could be readily recovered and recycled for at least five times without reduction of catalytic activity. The excellent performance of GO–NEt2–2N–Pdshould be ascribed to the neighborhood catalytic environment, the cooperative dual effect, as well as the robust immobilization interaction. The graphene-based support serves as an ideal platform to merge the two catalytic species together. What is more important, it provides a bridgefor the combination oftransition metal catalysis and organocatalysis.