Heterogeneous carbonate salt catalyzed acetylation of alcohols via a transesterification process has been devel- oped. Various esters are furnished up to 97% yield. Established procedure is simple and air-tolerant wit...Heterogeneous carbonate salt catalyzed acetylation of alcohols via a transesterification process has been devel- oped. Various esters are furnished up to 97% yield. Established procedure is simple and air-tolerant with readily available reagents. Ethyl acetate and isobutyl acetate are used as not only acetylating agents, but also reaction sol- vents in transesterification. Aliphatic linear alcohols, allylic alcohols and benzyl alcohols show high reactivities in the presence of 1 or 5 mol% Cs2CO3 at 125 ℃. Cesium carbonate can be recycled by pumping liquid phase out of reactor after reaction. During four cycle runs for reaction of 2-phenylethanol and ethyl acetate, high yields of phenethyl acetate are provided （〉60% yield）. Based on experiments and 1H NMR investigation, bifunctional catalysis is proposed, alcohol activated by carbonate ion is confirmed, and higher activity of catalytic amount than stoichiometric cesium carbonate is interpreted.展开更多
杨梅素是一种主要用于抗炎的多酚类黄酮化合物,为改善其水溶性和稳定性,合成了杨梅素-3-O-β-D-乳糖,并开发了一条高效的合成路线。首先以杨梅苷为起始原料,对杨梅苷的5位、7位、3′位、4′位和5′位酚羟基进行保护,形成五苄基保护的杨...杨梅素是一种主要用于抗炎的多酚类黄酮化合物,为改善其水溶性和稳定性,合成了杨梅素-3-O-β-D-乳糖,并开发了一条高效的合成路线。首先以杨梅苷为起始原料,对杨梅苷的5位、7位、3′位、4′位和5′位酚羟基进行保护,形成五苄基保护的杨梅苷。然后脱除3位鼠李糖,再与乙酰基保护的乳糖溴苷反应,最后通过依次脱去乙酰基和苄基得到目标化合物。经过路径优化,最终以更高效的方法合成了杨梅素-3-O-β-D-乳糖,减少了副产物的生成,提高了原合成路线总收率,此方法的总产率为44.5%。该路径得到了2个新型的杨梅素衍生物中间体。目标化合物的结构均经过1 H NMR,13 C NMR和HR-MS(ESI)确证。展开更多
Two-dimensional （2D） layered transition metal dichalcogenides （TMDs） have attracted enormous research interests and efforts towards the development of versatile electronic and optical devices, owing to their extra...Two-dimensional （2D） layered transition metal dichalcogenides （TMDs） have attracted enormous research interests and efforts towards the development of versatile electronic and optical devices, owing to their extraordinary and unique fundamental properties and remarkable prospects in nanoelectronic applications. Among the TMDs, tungsten diselenide （WSe2） exhibits tunable ambipolar transport characteristics and superior optical properties such as high quantum efficiency. Herein, we demonstrate significant enhancement in the device performance of WSe2 phototransistor by in situ surface functionalization with cesium carbonate （Cs2CO3）. WSe2 was found to be strongly doped with electrons after Cs2CO3 modification. The electron mobility of WSe2 increased by almost one order of magnitude after surface functionalization with 1.6-nm-thick Cs2CO3 decoration. Furthermore, the photocurrent of the WSe2-based phototransistor increased by nearly three orders of magnitude with the deposition of 1.6-nm-thick Cs2CO3. Characterizations by in situ photoelectron spectroscopy techniques confirmed the significant surface charge transfer occurring at the Cs2COB/WSe2 interface. Our findings coupled with the tunable nature of the surface transfer doping method establish WSe2 as a promising candidate for future 2D materials- based optoelectronic devices.展开更多
Catalytic amounts of cesium carbonate are sufficient to initiate the “silyl method”-type step-growth polymerization of phenylene-bis-TMS-ethers and -thioethers with activated aryl fluoride monomers, and can thus be ...Catalytic amounts of cesium carbonate are sufficient to initiate the “silyl method”-type step-growth polymerization of phenylene-bis-TMS-ethers and -thioethers with activated aryl fluoride monomers, and can thus be used instead of ce-sium fluoride or potassium carbonate. Cesium fluoride is very hygroscopic and potassium carbonate is generally used in equimolar amounts. The efficiency of catalytic amounts of cesium carbonate is demonstrated by the synthesis of poly(phenylene ether ether ketone) and poly(phenylene sulfide sulfone) examples.展开更多
Cesium carbonate supported on hydroxyapatite coated Nio.sZno.sFe2O4 magnetic nanoparticles （Nio.sZno.sFe2O4@Hap-Cs2CO3） was found to be magnetically separable, highly efficient, green and recyclable heterogeneous ca...Cesium carbonate supported on hydroxyapatite coated Nio.sZno.sFe2O4 magnetic nanoparticles （Nio.sZno.sFe2O4@Hap-Cs2CO3） was found to be magnetically separable, highly efficient, green and recyclable heterogeneous catalyst. The synthesized nanocatalyst has been characterized with several methods （FT-IR, SEM, TEM, XRD and XRF） and these analyzes confirmed which the cesium carbonate is well supported to catalyst surface. After full characterization, its catalytic activity was investigated in the synthesis of pyranopyrazole derivatives and the reactions were carried out at room temperature in 50：50 water/ethanol with excellent yields （88-95%）. More importantly, the Nio.5Zno.sFe204@Hap-Cs2CO3 was easily separated from the reaction mixture by external magnetic field and efficiently reused at least six runs without any loss of its catalytic activity. Thus, the developed nanomagnetic base catalyst is potentially useful for the green and economic production of organic compounds.展开更多
基金Project supported by the Natural Science Foundation Project of CQ CSTC （No. 2010BB5064）, Sharing Fund of Chongqing University＇s Large-Scale Equipment （No. 2010063040）, Scientific Research Fund of Chongqing University for the Introduction of Talent （No. CDJRC 10220004）, Innovative Talent Training Project of Chongqing University, the Third Stage of ＂211 Project＂ （No. S-09103） and Chongqing Municipal Education Commission Project （No. KJ-091201）.
文摘Heterogeneous carbonate salt catalyzed acetylation of alcohols via a transesterification process has been devel- oped. Various esters are furnished up to 97% yield. Established procedure is simple and air-tolerant with readily available reagents. Ethyl acetate and isobutyl acetate are used as not only acetylating agents, but also reaction sol- vents in transesterification. Aliphatic linear alcohols, allylic alcohols and benzyl alcohols show high reactivities in the presence of 1 or 5 mol% Cs2CO3 at 125 ℃. Cesium carbonate can be recycled by pumping liquid phase out of reactor after reaction. During four cycle runs for reaction of 2-phenylethanol and ethyl acetate, high yields of phenethyl acetate are provided （〉60% yield）. Based on experiments and 1H NMR investigation, bifunctional catalysis is proposed, alcohol activated by carbonate ion is confirmed, and higher activity of catalytic amount than stoichiometric cesium carbonate is interpreted.
文摘杨梅素是一种主要用于抗炎的多酚类黄酮化合物,为改善其水溶性和稳定性,合成了杨梅素-3-O-β-D-乳糖,并开发了一条高效的合成路线。首先以杨梅苷为起始原料,对杨梅苷的5位、7位、3′位、4′位和5′位酚羟基进行保护,形成五苄基保护的杨梅苷。然后脱除3位鼠李糖,再与乙酰基保护的乳糖溴苷反应,最后通过依次脱去乙酰基和苄基得到目标化合物。经过路径优化,最终以更高效的方法合成了杨梅素-3-O-β-D-乳糖,减少了副产物的生成,提高了原合成路线总收率,此方法的总产率为44.5%。该路径得到了2个新型的杨梅素衍生物中间体。目标化合物的结构均经过1 H NMR,13 C NMR和HR-MS(ESI)确证。
基金Acknowledgements W. C. acknowledges the financial support from Singapore MOE Grant R143-000-652-112, National Natural Science Foundation of China （No. 21573156） and the technical support from Centre for Advanced 2D Materials and Graphene Research Centre for the device fabrication. G. E. acknowledges Singapore National Research Foundation, Prime Minister＇s Office, Singapore, for funding the research under its Medium-sized Centre program as well as NRF Research Fellowship （No. NRF-NRFF2011-02）. G. E. also acknowledges financial support from Singapore MOE （No. MOE2015-T2-2-123）.
文摘Two-dimensional （2D） layered transition metal dichalcogenides （TMDs） have attracted enormous research interests and efforts towards the development of versatile electronic and optical devices, owing to their extraordinary and unique fundamental properties and remarkable prospects in nanoelectronic applications. Among the TMDs, tungsten diselenide （WSe2） exhibits tunable ambipolar transport characteristics and superior optical properties such as high quantum efficiency. Herein, we demonstrate significant enhancement in the device performance of WSe2 phototransistor by in situ surface functionalization with cesium carbonate （Cs2CO3）. WSe2 was found to be strongly doped with electrons after Cs2CO3 modification. The electron mobility of WSe2 increased by almost one order of magnitude after surface functionalization with 1.6-nm-thick Cs2CO3 decoration. Furthermore, the photocurrent of the WSe2-based phototransistor increased by nearly three orders of magnitude with the deposition of 1.6-nm-thick Cs2CO3. Characterizations by in situ photoelectron spectroscopy techniques confirmed the significant surface charge transfer occurring at the Cs2COB/WSe2 interface. Our findings coupled with the tunable nature of the surface transfer doping method establish WSe2 as a promising candidate for future 2D materials- based optoelectronic devices.
文摘Catalytic amounts of cesium carbonate are sufficient to initiate the “silyl method”-type step-growth polymerization of phenylene-bis-TMS-ethers and -thioethers with activated aryl fluoride monomers, and can thus be used instead of ce-sium fluoride or potassium carbonate. Cesium fluoride is very hygroscopic and potassium carbonate is generally used in equimolar amounts. The efficiency of catalytic amounts of cesium carbonate is demonstrated by the synthesis of poly(phenylene ether ether ketone) and poly(phenylene sulfide sulfone) examples.
基金Islamic Azad University,Bandar Abbas Branch for financial support
文摘Cesium carbonate supported on hydroxyapatite coated Nio.sZno.sFe2O4 magnetic nanoparticles （Nio.sZno.sFe2O4@Hap-Cs2CO3） was found to be magnetically separable, highly efficient, green and recyclable heterogeneous catalyst. The synthesized nanocatalyst has been characterized with several methods （FT-IR, SEM, TEM, XRD and XRF） and these analyzes confirmed which the cesium carbonate is well supported to catalyst surface. After full characterization, its catalytic activity was investigated in the synthesis of pyranopyrazole derivatives and the reactions were carried out at room temperature in 50：50 water/ethanol with excellent yields （88-95%）. More importantly, the Nio.5Zno.sFe204@Hap-Cs2CO3 was easily separated from the reaction mixture by external magnetic field and efficiently reused at least six runs without any loss of its catalytic activity. Thus, the developed nanomagnetic base catalyst is potentially useful for the green and economic production of organic compounds.
基金supported by the Natural Science Foundation of Guangdong Province(8451063201000074)the Innovation Project for Outstanding Young Scientists of Guangdong Province(LYM08021)the Youth Foundation of Jinan University(51208031)~~
