A very easy method is described here for direct preparation of palladium(II) carboxymethylcellulose (CMC-Pd II ) by ion exchange of sodium carboxymethylcellulose (CMC-Na) and PdCl 2 . When the resulting CMC-Pd II was employed as a catalyst in Suzuki−Miyaura and Mizoroki−Heck cross-coupling reactions, Pd II was reduced in situ to Pd 0 and further grown on CMC to afford carboxymethylcellulose-supported palladium nanoparticles (CMC-Pd 0 ). The as-generated CMC-Pd 0 proved to be an efficient catalyst for these mentioned cross-coupling reactions under mild aerobic conditions. The CMC-Pd II and CMCPd 0 were fully characterized by FT-IR, ICP-AES, XPS, XRD, SEM, EDX, TEM, and TGA. The characterized results demonstrated that the true catalytic species are Pd 0 nanoparticles. Moreover, the catalyst showed no significant loss of efficiency after six catalytic cycles.
A novel palladium(II) carboxymethylcellulose (CMC-Pd II ) was prepared by direct metathesis from sodium carboxymethylcellulose and PdCl 2 in aqueous solution. Its catalytic activities were explored for Heck-Matsuda reactions of aryldiazonium tetrafluoroborate with olefins, and Suzuki-Miyaura couplings of aryldiazonium tetrafluoroborate with arylboronic acid. Both reactions proceeded at room temperature in water or aqueous ethanol media without the presence of any ligand or base, to provide the corresponding cross-coupling products in good to excellent yields under atmospheric conditions. The CMC-Pd II and carboxymethylcellulose-supported palladium nanoparticles (CMC-Pd 0 ) formed in situ in the reactions were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, inductively coupled plasma atomic emission spectrometry, and scanning and transmission electron microscopies. The homogeneous nature of the CMC-Pd 0 catalyst was confirmed via Hg(0) and CS 2 poisoning tests. Moreover, the CMC-Pd 0 catalyst could be conveniently recovered by simple filtration and reused for at least ten cycles in Suzuki-Miyaura reactions without apparently losing its catalytic activity. The catalytic system not only overcomes the basic drawbacks of homogeneous catalyst recovery and reuse but also avoids the need to fabricate palladium nanoparticles in advance.
A one-pot tandem sequential protocol for efficient synthesis of a series of new pyranopyrazole derivatives has been developed involving Suzuki coupling of 4-bromobenzaldehyde and arylboronic acids followed by a four-component reaction from readily available ethyl acetoacetate, malononitrile, and hydrazine hydrate. All of the products were fully characterized by melting point, FTIR, 1 H NMR, and 13 C NMR spectroscopy, and HRMS. The structure of one of the products was further established by X-ray diffraction analysis. This method should provide a useful strategy for the construction of pyranopyrazole heterocycles.
Multicomponent reactions (MCRs) have emerged as a powerful tool for the construction of novel and complex molecular structures due to their advantages over conventional multistep synthesis. In their Full Paper on , Yiqun Li and co‐workers have developed a one‐pot, tandem, sequential, five component reaction (5CR) protocol for the synthesis of a wide range of biaryl‐substituted pyranopyrazole derivatives via Suzuki coupling of 4 ‐bromobenzaldehyde and phenylbronic acids followed by four‐component reaction of ethyl acetoacetate, malononitrile, and hydrazine hydrate without isolation and/or purification of intermediates.
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