The preparation of Cu nanoparticles by the aqueous solution reduction method was investigated. The effects of different reaction parameters on the preparation of Cu nanoparticles were studied. The optimum conditions f...The preparation of Cu nanoparticles by the aqueous solution reduction method was investigated. The effects of different reaction parameters on the preparation of Cu nanoparticles were studied. The optimum conditions for preparing well-dispersed nanoparticles were found as follows: 0.4 mol/L NaBH4 was added into solution containing 0.2 mol/L Cu2+, 1.0% gelatin dispersant in mass fraction, and 1.2 mol/L NH3?H2O at pH 12 and 313 K. In addition, a series of experiments were performed to discover the reaction process. NH3?H2O was found to be able to modulate the reaction process. At pH=10, Cu2+ was transformed to Cu(NH3)42+ as precursor after the addition of NH3?H2O, and then Cu(NH3)42+ was reduced by NaBH4 solution. At pH=12, Cu2+ was transformed to Cu(OH)2 as precursor after the addition of NH3?H2O, and Cu(OH)2 was then reduced by NaBH4 solution.展开更多
?β-Unsaturated amides with various substitution pattems at the carbon-carbon double And and nitrogen atom can be reduced to the corresponding saturated amides with high selectivity and yields with NaBH4/BiCl3 system.
The reduction reagents prepared from sodium borohydride, I-2 and a catalytic amount of chiral ferrocenyl amino alcohols 2a-e have been successfully applied to the enantioselective reduction of ketones. The optically a...The reduction reagents prepared from sodium borohydride, I-2 and a catalytic amount of chiral ferrocenyl amino alcohols 2a-e have been successfully applied to the enantioselective reduction of ketones. The optically active secondary alcohols were obtained in moderate enantiomeric excess and high chemical yield.展开更多
Cu nanoparticles (CuNPs) have been synthesized through an easy route by chemical reduction at room temperature. The Cu^2+ ions were reduced and stabilized with sodium borohydride and polyvinylpyrrolidone, respectively...Cu nanoparticles (CuNPs) have been synthesized through an easy route by chemical reduction at room temperature. The Cu^2+ ions were reduced and stabilized with sodium borohydride and polyvinylpyrrolidone, respectively. The effect of the variation of the reducing agent/precursor-salt (RA/PS) ratio on the size and morphology of the CuNPs was evaluated. The synthesized material was studied by ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The UV-Vis spectra showed a CuNPs plasmon peak at 569 nm and another peak belonging to Cu2O at 485 nm. XRD analysis showed the fcc-Cu phase with a small amount of fcc-Cu2O compound. SEM and TEM studies displayed that small semispherical CuNPs of approximately 7 nm were obtained at the RA/PS ratio of 2.6. The excess of polyvinylpyrrolidone stabilizer played an essential role in preventing CuNPs oxidation. On the other side, Cu2O polyhedral particles with larger sizes up to 150 nm were identified in the RA/PS ratio range of 2.0-1.84. In addition, Cu2O particles having star morphologies with quantum confinement at their tips were obtained at the RA/PS ratio of 1.66.展开更多
Five novel chiral ferrocenyl amino alcohols were prepared from natural amino acids and used as catalysts in the asymmetric reduction of prochiral ketones with NaBH 4/I 2 combination. The incorporation of the ferroce...Five novel chiral ferrocenyl amino alcohols were prepared from natural amino acids and used as catalysts in the asymmetric reduction of prochiral ketones with NaBH 4/I 2 combination. The incorporation of the ferrocenyl moiety into the molecule of the chiral amino alcohols greatly improved their enantioselectivity in the catalysis. The optically active secondary alcohols were obtained in moderate to good enantiomeric excesses and high chemical yields.展开更多
A combination of sodium borohydride and a catalytic amount of indium（Ⅲ） chloride in acetonitrile reduces imines formed in-situ from aldehydes and amines to the corresponding functionalised secondary and tertiary am...A combination of sodium borohydride and a catalytic amount of indium（Ⅲ） chloride in acetonitrile reduces imines formed in-situ from aldehydes and amines to the corresponding functionalised secondary and tertiary amines in moderate to good yields. Noteworthy is that highly chemoselective reactions were achieved in the presence of other functional groups such as halogens, carbon-carbon double bonds and hydroxyl groups.展开更多
The asymmetric reduction of prochiral ketones was catalyzed by a class of recoverable and highly stable chiral ferrocenyl amino alcohols derived from natural amino acids to yield optically active secondary alcohols in...The asymmetric reduction of prochiral ketones was catalyzed by a class of recoverable and highly stable chiral ferrocenyl amino alcohols derived from natural amino acids to yield optically active secondary alcohols in high chemical yields and moderate to good enantiomeric excesses.展开更多
Alloys based on non-noble metals could be the next generation of high-performance catalysts for many chemical reactions. However, precisely composition controlled synthesis of non-noble alloys remains a significant ch...Alloys based on non-noble metals could be the next generation of high-performance catalysts for many chemical reactions. However, precisely composition controlled synthesis of non-noble alloys remains a significant challenge. In this work, we report a simple synthesis of Cu_（0.5）Ni_（0.5） alloys without any component segregation. Its success relies on the use of Cu–Ni oxalate precursors, which are chelated in the proximity by oxalate ligands. One of the attractive features for the oxalate routes of catalyst preparation is that no classical support material is needed. The actual component ratios of the obtained Cu_（0.5）Ni_（0.5） alloy are consistent with the initial ratio. Cu_（0.5）Ni_（0.5） alloy shows a higher catalytic activity than pure Cu and Ni catalysts in the reduction of p-nitrophenol（4-NP） to p-aminophenol（4-AP） by sodium borohydride（NaBH4） in an aqueous solution, and the performance depends strongly on the strong interaction between Cu and Ni. The findings reported here are highly helpful to understand the relationship between the synergistic effects in alloys and their catalytic performance, and therefore could provide appropriate strategies to obtain desirable catalysts with improved activity in various catalytic applications.展开更多
文摘The preparation of Cu nanoparticles by the aqueous solution reduction method was investigated. The effects of different reaction parameters on the preparation of Cu nanoparticles were studied. The optimum conditions for preparing well-dispersed nanoparticles were found as follows: 0.4 mol/L NaBH4 was added into solution containing 0.2 mol/L Cu2+, 1.0% gelatin dispersant in mass fraction, and 1.2 mol/L NH3?H2O at pH 12 and 313 K. In addition, a series of experiments were performed to discover the reaction process. NH3?H2O was found to be able to modulate the reaction process. At pH=10, Cu2+ was transformed to Cu(NH3)42+ as precursor after the addition of NH3?H2O, and then Cu(NH3)42+ was reduced by NaBH4 solution. At pH=12, Cu2+ was transformed to Cu(OH)2 as precursor after the addition of NH3?H2O, and Cu(OH)2 was then reduced by NaBH4 solution.
文摘?β-Unsaturated amides with various substitution pattems at the carbon-carbon double And and nitrogen atom can be reduced to the corresponding saturated amides with high selectivity and yields with NaBH4/BiCl3 system.
文摘The reduction reagents prepared from sodium borohydride, I-2 and a catalytic amount of chiral ferrocenyl amino alcohols 2a-e have been successfully applied to the enantioselective reduction of ketones. The optically active secondary alcohols were obtained in moderate enantiomeric excess and high chemical yield.
基金the National Council of Science and Technology (Conacyt) of Mexico for the financial support
文摘Cu nanoparticles (CuNPs) have been synthesized through an easy route by chemical reduction at room temperature. The Cu^2+ ions were reduced and stabilized with sodium borohydride and polyvinylpyrrolidone, respectively. The effect of the variation of the reducing agent/precursor-salt (RA/PS) ratio on the size and morphology of the CuNPs was evaluated. The synthesized material was studied by ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The UV-Vis spectra showed a CuNPs plasmon peak at 569 nm and another peak belonging to Cu2O at 485 nm. XRD analysis showed the fcc-Cu phase with a small amount of fcc-Cu2O compound. SEM and TEM studies displayed that small semispherical CuNPs of approximately 7 nm were obtained at the RA/PS ratio of 2.6. The excess of polyvinylpyrrolidone stabilizer played an essential role in preventing CuNPs oxidation. On the other side, Cu2O polyhedral particles with larger sizes up to 150 nm were identified in the RA/PS ratio range of 2.0-1.84. In addition, Cu2O particles having star morphologies with quantum confinement at their tips were obtained at the RA/PS ratio of 1.66.
文摘Five novel chiral ferrocenyl amino alcohols were prepared from natural amino acids and used as catalysts in the asymmetric reduction of prochiral ketones with NaBH 4/I 2 combination. The incorporation of the ferrocenyl moiety into the molecule of the chiral amino alcohols greatly improved their enantioselectivity in the catalysis. The optically active secondary alcohols were obtained in moderate to good enantiomeric excesses and high chemical yields.
文摘A combination of sodium borohydride and a catalytic amount of indium（Ⅲ） chloride in acetonitrile reduces imines formed in-situ from aldehydes and amines to the corresponding functionalised secondary and tertiary amines in moderate to good yields. Noteworthy is that highly chemoselective reactions were achieved in the presence of other functional groups such as halogens, carbon-carbon double bonds and hydroxyl groups.
文摘The asymmetric reduction of prochiral ketones was catalyzed by a class of recoverable and highly stable chiral ferrocenyl amino alcohols derived from natural amino acids to yield optically active secondary alcohols in high chemical yields and moderate to good enantiomeric excesses.
基金financially supported by NNSFC(No.21025104 and 21271171)
文摘Alloys based on non-noble metals could be the next generation of high-performance catalysts for many chemical reactions. However, precisely composition controlled synthesis of non-noble alloys remains a significant challenge. In this work, we report a simple synthesis of Cu_（0.5）Ni_（0.5） alloys without any component segregation. Its success relies on the use of Cu–Ni oxalate precursors, which are chelated in the proximity by oxalate ligands. One of the attractive features for the oxalate routes of catalyst preparation is that no classical support material is needed. The actual component ratios of the obtained Cu_（0.5）Ni_（0.5） alloy are consistent with the initial ratio. Cu_（0.5）Ni_（0.5） alloy shows a higher catalytic activity than pure Cu and Ni catalysts in the reduction of p-nitrophenol（4-NP） to p-aminophenol（4-AP） by sodium borohydride（NaBH4） in an aqueous solution, and the performance depends strongly on the strong interaction between Cu and Ni. The findings reported here are highly helpful to understand the relationship between the synergistic effects in alloys and their catalytic performance, and therefore could provide appropriate strategies to obtain desirable catalysts with improved activity in various catalytic applications.
