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331.
Fiorilli S Camarota B Garrone E Onida B 《Physical chemistry chemical physics : PCCP》2011,13(3):1201-1209
Proton-donor ability of carboxylic groups incorporated by co-condensation into SBA-15 and ethane-bridged periodic mesoporous organosilica (PMO) has been studied through IR spectroscopy by dosing ammonia, which forms reversibly COO(-) groups and NH(4)(+) ions. The related equilibrium constants, determined by elaboration of IR data, reveal a lower reactivity of -COOH groups at the surface of PMO than on SBA-15, when the two samples have been outgassed at the same temperature. This finding is interpreted in terms of different dielectric constants and intermolecular interactions engaged with the surface species. Carboxylic groups on ethane-bridged organosilica react with silanols upon thermal treatment at 473 K to form a mixed anhydride species Si-O-C(O)-, at variance with the same groups on SBA-15. 相似文献
332.
Said Rabbani Federica Compostella Laura Franchini Beatrice Wagner Beat Ernst 《Journal of carbohydrate chemistry》2013,32(8-9):789-807
Various fundamental biologic roles of milk oligosaccharides have been recognized; however, their structure‐affinity relationship is still not fully revealed. Herein, we describe the synthesis of the fluorescent‐labeled milk oligosaccharides 3‐(5‐dimethylaminonaphthalene‐1‐sulfonylamino)propyl β‐D‐galactopyranosyl‐(1→3)‐[α‐L‐fucopyranosyl‐(1→4)]‐2‐acetamido‐2‐deoxy‐β‐D‐glucopyranoside (1) and 3‐(5‐dimethylamino‐naphthalene‐1‐sulfonylamino)propyl β‐D‐galactopyranosyl‐(1→3)‐[α‐L‐fucopyranosyl‐(1→4)]‐β‐D-glucopyranoside (2) as useful tools for synthetic, analytic, and biologic applications. For the fucosylation of lactose and lacto‐N‐biose, the chemical and the enzymatic syntheses using fucosyltransferase III were compared. 相似文献
333.
Olga Bortolini Antonio De Nino Angelo Garofalo Loredana Maiuolo Beatrice Russo 《合成通讯》2013,43(16):2483-2487
Basic hydrogen peroxide and sodium perborate were found to be cheap and efficient alternatives for the conversion of primary and secondary nitro to carbonyl compounds (Nef reaction) in ionic liquids. 相似文献
334.
Ranieri B Curti C Battistini L Sartori A Pinna L Casiraghi G Zanardi F 《The Journal of organic chemistry》2011,76(24):10291-10298
A reliable, catalytic asymmetric vinylogous Mukaiyama-Mannich reaction of pyrrole-based silyl dienolates is introduced that is particularly apt for alkyl- and α-alkoxyalkyl-substituted aldehydes. The reaction course is effectively orchestrated by the Hoveyda-Snapper amino acid-based chiral ligand/silver(I) catalyst combination to produce valuable vicinal diamino carbonyl compounds in high yields, with virtually complete γ-site- and anti-selectivity and significant catalyst-to-product chirality transfer. The utility of the Mannich products can be seen in the synthesis of an unprecedented perhydrofuro[3,2-b]pyrrolone product, an aza-analogue of naturally occurring (+)-goniofufurone. 相似文献
335.
Werncke CG Limberg C Knispel C Metzinger R Braun B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(10):2931-2938
By employing the 2,2'-thiobis(2,4-di-tert-butylphenolate) ligand ((S)L(2-)) a novel oxovanadium(V) complex, (PPh(4))(2)[(S)LV(O)(μ(2)-O)(2)V(O)(S)L] (1), was synthesised that exhibits haloperoxidase activity: on addition of H(2)O(2) a sequence of successive peroxide formation and intramolecular thioether oxidation events (sulfoxide and sulfone) led to a mixture of five products, which were all identified unambiguously, partly through an independent synthesis and characterisation. It was shown that internal thioether oxidation proceeds through peroxide formation, but the sulfoxidation of external thioether functions requires further activation of the peroxide function by protons or alkyl cations. Consistently, the employment of tBuOOH instead of H(2)O(2) led to a very active system for the catalytic sulfoxidation of thioethers. 相似文献
336.
Beatrice Lansbergen Srija Tewari Ireneusz Tomczyk Maik Seemann Henning Louis Buchholz Mike Rippegarten Daniel Chamier Cieminski Dr. Fabio Juliá Prof. Dr. Tobias Ritter 《Angewandte Chemie (International ed. in English)》2023,62(52):e202313659
We report the first reductive vinylation of alkyl iodides. The reaction uses a vinyl thianthrenium salt, a palladium catalyst, and an alkyl zinc intermediate formed in situ to trap the LnPdII(vinyl) complex formed after oxidative addition before it undergoes undesired homocoupling to form butadiene. 相似文献
337.
Vishal Budhija Phebe H. van Langevelde Konstantin B. Krause Dr. Beatrice Cula Dr. D. G. H. Hetterscheid Dr. Matthias Schwalbe 《欧洲无机化学杂志》2023,26(14):e202200743
Synthesis, characterization and reactivity studies of a hetero-dicopper complex, particularly towards oxygen reduction are presented. A bischlorido copper(II) trishistidine-type coordination unit is positioned directly above a copper porphyrin unit. The close distance between the two coordination fragments is secured by a rigid xanthene backbone. Surprisingly, the dinuclear complex is not active towards oxygen reduction unlike the earlier published mononuclear analogues with a bispyridylamine copper center. However, the compound architecture of this multinuclear metal complex is interesting and can play an important role in the development of new catalysts for ORR. 相似文献
338.
The C−F bond activation of pentafluoropyridine and 2,3,5,6-tetrafluoropyridine at [Ni(cod)2] (cod=1,5-cyclooctadiene) in the presence of the phosphine PPh2(Ind) (Ind=3-methyl-2-indolyl) led to the formation of the nickel(II) fluorido bis(phosphine) complexes trans-[Ni(F)(2-C5NF4){PPh2(Ind)}2] and trans-[Ni(F)(2-C5HNF3){PPh2(Ind)}2]. The complexes are characterized by the presence of intramolecular hydrogen bonds between the NH group of the phosphine ligands and the fluorido ligand. Stochiometric model reactions of nickel(II) fluorido complexes with PhB(OH)2 revealed that the former can be considered as intermediates in Suzuki–Miyaura cross coupling reactions. Catalytic experiments were attempted using 10 mol-% of trans-[Ni(F)(2-C5NF4){PPh2(Ind)}2] as catalyst and the activities of the PPh2(Ind) complex were compared to the ones of an analogous nickel(II) fluorido complex, bearing PPh3 instead of PPh2(Ind) as ligands. The latter exhibited a somewhat lower catalytic activity suggesting a slight influence of the H-bonds in the outer coordination sphere. 相似文献
339.
Aneta Slodczyk Philippe Colomban Stephanie Willemin Olivier Lacroix Beatrice Sala 《Journal of Raman spectroscopy : JRS》2009,40(5):513-521
OH− and H3O+ species in hydrates and simple oxides are rather well characterised from their IR, Raman and inelastic neutron points of view. For the H+ (H2O) species in solid state the variability is well established and assignment remains discussed. The question of the vibrational signature of isolated proton (e.g. the ionic proton, a proton sharing its interaction with more than two acceptors) and its dynamic nature (proton gas, polaron,…) is open. H+‐containing modified perovskites A(Ba,Sr,…) B(Zr,Ce,Ti,…) O3 are potential ceramic membranes for fuel cell and medium temperature water electrolysis (300–800 °C). Comparison studies of the protonated and non‐protonated lanthanide/rare earth‐modified perovskites of type Ba(Sr)Zr(Ti)O3 as well as Al‐modified BaTiO3 show that a broad component centred at 2500 cm−1 is observed after ‘proton insertion’. Its intensity is correlated to the protonic species content as well as to the conductivity of the materials. The mixed nature of this feature is discussed: fluorescence related to the dangling bonds, A, B, C bands or new phenomena related to the ionic protons and associated electronic defect. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献