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Summary Optically pure (+)-beta-eudesmol is a possible starting material for the synthesis of several termite defense compounds. A
two step procedure for the isolation of gram quantities of (+)-beta-eudesmol from commercially availableAmyris balsamifera oil (syn. West Indian sandalwood oil), containing 8% beta-eudesmol, was developed. Step one consisted of an efficient vacuum
distillation of the total oil. Step two was a medium pressure LC separation with an AgNO3 impregnated silica gel stationary phase. Several other separation procedures failed due to the presence of many closely related
sesquiterpene alcohols (75% of the oil). 相似文献
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Ana E. Platero-Prats Concepción López Xavier Solans Piet W.N.M. van Leeuwen Gino P.F. van Strijdonck 《Journal of organometallic chemistry》2007,692(20):4215-4226
A study of the reactivity of enantiopure ferrocenylimine (SC)-[FcCHN-CH(Me)(Ph)] {Fc = (η5-C5H5)Fe{(η5-C5H4)-} (1a) with palladium(II)-allyl complexes [Pd(η3-1R1,3R2-C3H3)(μ-Cl)]2 {R1 = H and R2 = H (2), Ph (3) or R1 = R2 = Ph (4)} is reported. Treatment of 1a with 2 or 3 {in a molar ratio Pd(II):1a = 1} in CH2Cl2 at 298 K produced [Pd(η3-3R2-C3H4){FcCHN-CH(Me)(Ph)}Cl] {R2 = H (5a) or Ph (6a)}. When the reaction was carried out under identical experimental conditions using complex 4 as starting material no evidence for the formation of [Pd(η3-1,3-Ph2-C3H3){FcCHN-CH(Me)(Ph)}Cl] (7a) was found. Additional studies on the reactivity of (SC)-[FcCHN-CH(R3)(CH2OH)] {R3 = Me (1b) or CHMe2 (1c)} with complex 4 showed the importance of the bulk of the substituents on the palladium(II) allyl-complex (2-4) or on the ferrocenylimines (1) in this type of reaction. The crystal structure of 5a showed that: (a) the ferrocenylimine adopts an anti-(E) conformation and behaves as an N-donor ligand, (b) the chloride is in acis-arrangement to the nitrogen and (c) the allyl group binds to the palladium(II) in a η3-fashion. Solution NMR studies of 5a and 6a and [Pd(η3-1,3-Ph2-C3H3){FcCHN-CH(Me)(CH2OH)}Cl] (7b) revealed the coexistence of several isomers in solution. The stoichiometric reaction between 6a and sodium diethyl 2-methylmalonate reveals that the formation of the achiral linear trans-(E) isomer of Ph-CHCH-CH2Nu (8) was preferred over the branched derivative (9). A comparative study of the potential utility of ligand 1a, complex 5a and the amine (SC)-H2N-CH(Me)(Ph) (11) as catalysts in the allylic alkylation of (E)-3-phenyl-2-propenyl (cinnamyl) acetate with the nucleophile diethyl 2-methylmalonate (Nu−) is reported. 相似文献
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Platero-Prats AE de la Peña-O'Shea VA Proserpio DM Snejko N Gutiérrez-Puebla E Monge A 《Journal of the American Chemical Society》2012,134(10):4762-4771
This work is to emphasize the influence of the synthetic procedures in the isolation of different coordination polymers that coexist under hydro-/solvothermal conditions. An experimental and theoretical study in the Mg(2+):4,4'-(hexafluoroisopropylidene)bis(benzoic acid):1,10-phenantroline system has been carried out. Computational studies have determined the relative energies for those compounds that coexist under certain hydrothermal conditions, and have helped to identify the driving forces for the formation of the different phases. The five new compounds belong to five different structural types: AEPF-14, which presents two polymorphs (α- and β-) ([Mg(H(2)O)(4)(phen)(2)]L), AEPF-15 ([Mg(HL)(2)(phen)]) and AEPF-16 ([Mg(H(2)O)(2)(L)(phen)]) are both 1D MOFs (AEPF-16 with a helical structure), and AEPF-17 ([Mg(H(2)O)(L)(phen)]) with a 2D structure. Hydrogen bond interactions found in the five compounds have been taken into account to study the topology of their supramolecular nets. Finally, dehydration studies performed on AEPF-14 (α- and β-) and AEPF-16 have shown that the topological type of their supramolecular networks determines the structural changes that take place during the dehydration processes of these Mg compounds. 相似文献
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A. Sosa E. Bravin J. Harasimowicz A. Jeff C. P. Welsch The AEḡIS collaboration 《Hyperfine Interactions》2014,229(1-3):169-174
Detailed diagnostic of antiproton beams at low energies is required for essentially all experiments at the Antiproton Decelerator (AD), but will be particularly important for the future Extra Low ENergy Antiproton ring (ELENA) and its keV beam lines to the different experiments. Many monitors have been successfully developed and operated at the AD, but in particular beam profile monitoring remains a challenge. A dedicated beam instrumentation and detector test stand has recently been setup at the AE \(\bar {g}\) IS experiment (Antimatter Experiment: Gravity, Interferometry, Spectroscopy). Located behind the actual experiment, it allows for parasitic use of the antiproton beam at different energies for testing and calibration. With the aim to explore and validate different candidate technologies for future low energy beam lines, as well as the downstream antihydrogen detector in AE \(\bar {g}\) IS, measurements have been carried out using Silicon strip and pixel detectors, a purpose-built secondary emission monitor and emulsions. Here, results from measurements and characterization of the different detector types with regard to their future use at the AD complex are presented. 相似文献
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Ignacio Romero-Muñiz Dr. Andreas Mavrandonakis Pablo Albacete Alicia Vega Dr. Valérie Briois Prof. Félix Zamora Dr. Ana E. Platero-Prats 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(31):13113-13120
Layered covalent organic frameworks (2D-COFs), composed of reversible imine linkages and accessible pores, offer versatility for chemical modifications towards the development of catalytic materials. Nitrogen-enriched COFs are good candidates for binding Pd species. Understanding the local structure of reacting Pd sites bonded to the COF pores is key to rationalize interactions between active sites and porous surfaces. By combining advanced synchrotron characterization methods with periodic computational DFT modeling, the precise atomic structure of catalytic Pd sites attached to local defects is resolved within an archetypical imine-linked 2D-COF. This material was synthesized using an in situ method as a gel, under which imine hydrolysis and metalation reactions are coupled. Local defects formed in situ within imine-linked 2D-COF materials are highly reactive towards Pd metalation, resulting in active materials for Suzuki–Miyaura cross-coupling reactions. 相似文献
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Covalent radii revisited 总被引:1,自引:0,他引:1
Cordero B Gómez V Platero-Prats AE Revés M Echeverría J Cremades E Barragán F Alvarez S 《Dalton transactions (Cambridge, England : 2003)》2008,(21):2832-2838
A new set of covalent atomic radii has been deduced from crystallographic data for most of the elements with atomic numbers up to 96. The proposed radii show a well behaved periodic dependence that allows us to interpolate a few radii for elements for which structural data is lacking, notably the noble gases. The proposed set of radii therefore fills most of the gaps and solves some inconsistencies in currently used covalent radii. The transition metal and lanthanide contractions as well as the differences in covalent atomic radii between low spin and high spin configurations in transition metals are illustrated by the proposed radii set. 相似文献
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