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31.
Jos Luis Mata‐Mata J. Alfredo Gutirrez M. Angeles Paz‐Sandoval Amira R. Madrigal Antonio Martínez‐Richa 《Journal of polymer science. Part A, Polymer chemistry》2006,44(24):6926-6942
End‐functionalized polyesters have been synthesized by ring‐opening polymerization (ROP) of ?‐caprolactone (CL) initiated with five different ruthenium derivatives in the presence of a series of alcohols as transfer agents. Mechanistic studies were performed for ROP of CL with RuCl2(PPh3)3 ( I ), TpRuCl(PPh3)2 ( II ), and TpRuCl(PHPh2)(PPh3) ( III ) as catalysts in the presence or absence of benzyl alcohol (BzOH). Obtained molecular weights are proportional to CL/BzOH ratio, but there is not a direct relationship with CL/ruthenium complex ratios. 1H and 13C NMR spectroscopy revealed the existence of benzyl ester end‐groups. Catalysis involves (a) dissociation of ruthenium complexes, (b) coordination of the lactone CL, (c) coordination of the BzOH with the formation of a metal alkoxide, (d) transfer from the alkoxyl ligand to the coordinated lactone, and (e) ring‐opening of CL by oxygen‐acyl bond cleavage. The proposed mechanism is supported by 1H, 13C, and 31P NMR, gel permeation chromatography (GPC), and MALDI‐TOF analysis of the polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6926–6942, 2006 相似文献
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Yuji Nakano Michael J. Black Andrew J. Meichan Braddock A. Sandoval Megan M. Chung Kyle F. Biegasiewicz Tianyu Zhu Todd K. Hyster 《Angewandte Chemie (International ed. in English)》2020,59(26):10484-10488
Flavin‐dependent ‘ene’‐reductases (EREDs) are highly selective catalysts for the asymmetric reduction of activated alkenes. This function is, however, limited to enones, enoates, and nitroalkenes using the native hydride transfer mechanism. Here we demonstrate that EREDs can reduce vinyl pyridines when irradiated with visible light in the presence of a photoredox catalyst. Experimental evidence suggests the reaction proceeds via a radical mechanism where the vinyl pyridine is reduced to the corresponding neutral benzylic radical in solution. DFT calculations reveal this radical to be “dynamically stable”, suggesting it is sufficiently long‐lived to diffuse into the enzyme active site for stereoselective hydrogen atom transfer. This reduction mechanism is distinct from the native one, highlighting the opportunity to expand the synthetic capabilities of existing enzyme platforms by exploiting new mechanistic models. 相似文献
34.
Imelda T. Sandoval Elizabeth J. Manos Ryan M. Van Wagoner Richard Glenn C. Delacruz Kornelia Edes Dennis R. Winge Chris M. Ireland David A. Jones 《Chemistry & biology》2013,20(6):753-763
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35.
J. Reyes Miranda A. García Murillo F. de J. Carrillo Romo J. Oliva Uc C. A. Flores Sandoval A. de J. Morales Ramírez S. Velumani E. de la Rosa Cruz V. Garibay Febles 《Journal of Sol-Gel Science and Technology》2014,72(3):435-442
BaTiO3:(5 %)Eu3+ nanoparticles and BaTiO3:(5 %)Eu3+@SiO2 composites were synthesized by the solvothermal method. The effects on the structure, morphology and luminescent properties were studied using samples with different molar ratios of BaTiO3:(5 %)Eu3+@SiO2: 60:40, 50:50, 40:60, 30:70, 20:80, 10:90, 08:92, 6.5:93.5, 05:95, and 1.5:98.5. When the amount of silica in the composites was increased, the orange emission of Eu3+ increased, too; this was observed by exciting the charge transfer band centered at 283 nm. Furthermore, an increase in the intensity of the emission was obtained under excitation at 394 nm as a consequence of the improvement in the crystallinity of the samples. The presence of silica and the degree of crystallinity of the samples were determined through the Fourier transform infrared spectra and X-ray diffraction patterns. All of the results suggest that our ceramic material could be a good candidate for biomedical applications such as biolabeling, since the luminescence of BaTiO3:(5 %)Eu3+@SiO2 composites have an emission intensity higher than that of nanoparticles composed solely of BaTiO3:Eu3+. This work demonstrates that BaTiO3:Eu3+@SiO2 composites have an emission intensity higher than that of nanoparticles composed solely of BaTiO3:Eu3+. 相似文献
36.
Corts C. Eduardo Corts R. Eduardo Roberto Martínez Gustavo Avila Arturo Sandoval 《Journal of heterocyclic chemistry》1989,26(6):1561-1562
The preparation of several 5,4-disubstituted 3-methylisoxazoles is described. The structure of all products was corroborated by ir, 1H-nmr and mass spectrometry. 相似文献
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Dr. Yuji Nakano Michael J. Black Andrew J. Meichan Braddock A. Sandoval Megan M. Chung Dr. Kyle F. Biegasiewicz Dr. Tianyu Zhu Prof. Dr. Todd K. Hyster 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(26):10570-10574
Flavin-dependent ‘ene’-reductases (EREDs) are highly selective catalysts for the asymmetric reduction of activated alkenes. This function is, however, limited to enones, enoates, and nitroalkenes using the native hydride transfer mechanism. Here we demonstrate that EREDs can reduce vinyl pyridines when irradiated with visible light in the presence of a photoredox catalyst. Experimental evidence suggests the reaction proceeds via a radical mechanism where the vinyl pyridine is reduced to the corresponding neutral benzylic radical in solution. DFT calculations reveal this radical to be “dynamically stable”, suggesting it is sufficiently long-lived to diffuse into the enzyme active site for stereoselective hydrogen atom transfer. This reduction mechanism is distinct from the native one, highlighting the opportunity to expand the synthetic capabilities of existing enzyme platforms by exploiting new mechanistic models. 相似文献
39.
Bio-solvents are good alternative solvents that avoid the use of classical organic solvents when performing enzymatic reactions. A noticeably change in regioselectivity was observed in the synthetic behaviour of Biolacta β-galactosidase using bio-solvents derived from dimethylamide and glycerol as co-solvents. Under these conditions, the enzyme changes its well known tendency to produce β-(1→4) to β-(1→6) disaccharides. An evaluation of the bio-solvent concentration and the effects of the non proteic additives in commercially available Biolacta β-galactosidase was undertaken in order to optimize the reaction conditions to improve the yield of the β-(1→6) product. 相似文献