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51.
Guido Kickelbick Dieter Rutzinger Thomas Gallauner 《Monatshefte für Chemie / Chemical Monthly》2002,133(8):1157-1164
Summary. Hexadentate ligands were formed by the reaction of primary dimethylaminoethyl- or methoxyethylamines with formaldehyde. The
resulting N, N′, N″-functionalized hexahydro-1,3,5-triazines contain pending amino or ether functionalities which are able to coordinate to
metals in addition to the ring nitrogen atoms. Both ligands were reacted with CuBr, and novel tricopper clusters were isolated
and characterized by X-ray structure analysis. In these compounds a ring nitrogen atom, the pending amino or ether functionality,
and two bridging bromine atoms coordinate each of the copper atoms.
Received January 22, 2002; accepted (revised) March 22, 2002 相似文献
52.
Perfluoroalkyl iodine compounds: preparations and properties of CF3IO, CF3IOF2, and CF3IO2. The trifluoromethyl iodine compounds CF3IO, CF3IOF2, and CF3IO2 are formed from the reactions of CF3I, CF3IF2 or CF3IF4 with ozone or silicon dioxide respectively. Their preparartions, properties, 19F-nmr spectra, and ir spectra are described. 相似文献
53.
Dieter Seebach Laurent Schaeffer Franois Gessier Pascal Bindschdler Corinna Jger Delphine Josien Sascha Kopp Grald Lelais YogeshR. Mahajan Peter Micuch Radovan Sebesta BerndW. Schweizer 《Helvetica chimica acta》2003,86(6):1852-1861
Multigram amounts of suitably protected β2‐amino acids with 17 of the 20 proteinogenic side chains are prepared by diastereoselective reactions of Li, B, or Ti enolates of the corresponding 3‐acyl‐4‐isopropyl‐5,5‐diphenyloxazolidin‐2‐ones (acyl‐DIOZ; 1 ) with appropriate electrophiles (amidomethylation, hydroxyalkylation, (benzyloxycarbonyl)methylation) in yields of 55–90% and with diastereoselectivities of 80 to >97% (Scheme). The primary products 2 – 8 thus obtained are converted to protected β2‐amino acids by standard procedures (Table 1). Many of the DIOZ derivatives are highly crystalline compounds (31 X‐ray crystal structures in Table 2). The chiral auxiliary DIOZ, readily prepared in either enantiomeric form, is recovered with high yield. 相似文献
54.
Monodisperse Linear and Cyclic Oligo[(R)-3-hydroxybutanoates] Containing up to 128 Monomeric Units Using benzyl ester/(tert-butyl)diphenylsilyl ether protection, (COCl)2/pyridine esterification conditions, and a fragment-coupling strategy (with H2/Pd-C debenzylation and HF · pyridine desilylation), linear oligomers of (R)-3-hydroxybutanoic acid (3-HB) containing up to 128 3-HB building blocks (mol. weight > 11 000 Da) are assembled (Schemes 1,2,5, and 6). In contrast to the previously employed protecting-group combination, and due to the low-temperature esterifying conditions, this procedure leads to monodisperse oligomers: all steps occur without loss of single 3-HB units. The product oligomers with two, one, and no terminal protecting groups (mostly prepared in multi-gram amounts) are characterized by all standard spectroscopic methods, especially by mass spectroscopy (Figs. 2 and 3), by their optical activity, and by elemental analyses. Cyclization of the oligo[(R)-3-hydroxybutanoic acids] with up to 32 3-HB units, using thiopyridine activation and CuBr2 for the ring closure, produces oligolides consisting of up to 128 ring atoms (Scheme 7). Mixed oligolides containing 3-HB and (R)-3-hydroxypentanoic units are prepared from the corresponding linear trimers, using Yamaguchi's method for the ring closure (Scheme 8 and Fig.4 (X-ray crystal structures of two folded conformers)). Comparisons of melting points (Table 1), of [α] values (Tables 2 and 3), of 1H-NMR coupling constants (Table 3), and of molecular volume/hydroxyalkanoate unit (Table 4) of linear and cyclic oligomer derivatives and of the high-molecular-weigh polymer show that the monodisperse oligomers appear to be surprisingly good models for the polymer. Besides this insight, our synthesis is supplying the samples to further test the role of P(3-HB) (ca. 140 units) as a component of complexes forming channels through cell-wall phospholipid bilayers. 相似文献
55.
Stir bar sorptive extraction based on restricted access material for the direct extraction of caffeine and metabolites in biological fluids 总被引:2,自引:0,他引:2
A biocompatible stir bar sorptive extraction (SBSE) device was prepared using an alkyl-diol-silica (ADS) restricted access material (RAM) as the SBSE coating. The RAM-SBSE bar was able to simultaneously fractionate the protein component from a biological sample, while directly extracting caffeine and its metabolites, overcoming the present disadvantages of direct sampling in biological matrices by SBSE, such as fouling of the extraction coating by proteins. Desorption of the analytes was performed by stirring the bar in a water/ACN mixture (3/1, v/v) and subsequently reconcentrating the sample solution in water to enable HPLC-UV analysis to be performed. The limit of detection, based on a signal to noise ratio of 3, for caffeine was 25 ng/mL in plasma. The method was confirmed to be linear over the range of 0.5-100 microg/mL of caffeine with an average linear coefficient (R2) value of 0.9981. The injection repeatability and intra-assay precision of the method were evaluated over ten injections, resulting in a %RSD of approximately 8%. The RAM-SBSE device was robust (>50 extraction in plasma without significant signal loss) and simple to use, providing many direct extractions and subsequent determination of caffeine and its metabolites in biological fluids. In contrast to existing sample preparation methods for the analysis of caffeine and selected metabolites in biological fluids, this feasibility study using a biocompatible SBSE approach was advantageous in terms of simplifying the sample preparation procedures. 相似文献
56.
CF3I(OCOCF3)2 is formed from the reactions of CF3IF2 or CF3IO with trifluoroacetic anhydride at low temperature. During the reaction of CF3IF2 with (CF3CO)2O CF3IF(OCOCF3) is formed as an intermediate product. The preparation, the 19F-nmr spectra and the thermal decomposition are described. 相似文献
57.
In situ observations of water production and distribution in an operating H2/O2 PEM fuel cell assembly using 1H NMR microscopy 总被引:1,自引:0,他引:1
Feindel KW LaRocque LP Starke D Bergens SH Wasylishen RE 《Journal of the American Chemical Society》2004,126(37):11436-11437
Proton NMR imaging was used to investigate in situ the distribution of water in a polymer electrolyte membrane fuel cell operating on H2 and O2. In a single experiment, water was monitored in the gas flow channels, the membrane electrode assembly, and in the membrane surrounding the catalysts. Radial gradient diffusion removes water from the catalysts into the surrounding membrane. This research demonstrates the strength of 1H NMR microscopy as an aid for designing fuel cells to optimize water management. 相似文献
58.
The diastereoselectivity of the mercuration of acyclic alkenes can be reversed by changing the substituent in the allylic position; with alcohols the erythro isomers and with esters or hemiacetals the threo isomers and are formed predominantly (Table I). 相似文献
59.
On Ternary Chalcogenides. XXIV. The Structure of TlGaSe2 TlGaSe2 is monoclinic with a = 10.772(3), b = 10.771(5), c = 15.636(8) Å, ß = 100.6(3)°, Z = 16, space group Cc. The refinement yielded an R value of 0.082 for 1366 unique observed reflections (MoKα). The compound crystallizes with a layer structure with two anion layers perpendicular to c* in the unit cell. The structural motive of the layers are large corner-linked Ga4Se10- tetraeder consisting of four corner-linked GaSe4 tetrahedra. Two adjacent layers are turned relative to each other by 90°. They are kept together by Tl1+ ions, which are situated on straight lines parallel to the edges of the Ga4Se10 groups. They are surrounded by six selenium atoms forming trigonal-prismatic TlSe6 polyhedra. 42 screw-axes within the layers are the reason for a strongly pronounced pseudo tetragonal symmetry. Different possibilities of stacking cause a onedimensional disorder along the c* direction. The relations between the TlGaSe2 type and the TlSe type and also the high-pressure modifications of some compounds with the TlGaSe2 structure are discussed. 相似文献
60.
Jolanta Olkowska‐Oetzel Dieter Fenske Petra Scheer Andreas Eichhfer 《无机化学与普通化学杂志》2003,629(3):415-420
Syntheses and Thermal Properties of Cluster Molecules, formed from Groups 11‐13‐16 Elements In the presence of PPh3, CuX (X = Cl, CH3COO) or AgOC(O)C6H5 and GaCl3 react in THF with S(SiMe3)2 or Se(SiMe3)2 to yield [Cu6Ga8Cl4S13(PPh3)6] ( 1 ), [Cu6Ga8Cl4Se13(PPh3)6] ( 2 ), [Ag6Ga8Cl4S13(PPh3)6] ( 4 ) and [Ag6Ga8Cl4Se13(PPh3)6] ( 5 ). The use of PnPr2Ph instead of PPh3 and subsequent layering with n‐hexane leads to the formation of the cluster [Cu6Ga8Cl4Se13(PnPr2Ph)12] ( 3a , 3b ). Reaction of CuCl, GaCl3 and PnPr3 with Se(SiMe3)2 in THF results in the crystallisation of the ionic cluster (HPnPr3)2[Cu2Ga4Cl4Se6(PnPr3)4] ( 6 ). The structures of 1 — 6 were determined by X‐ray single crystal structure analysis. Thermogravimetric measurements of the cluster molecules and powder diffraction patterns of the remaining powders reveal the potential use of them as single source precursor compounds for the synthesis of the related ternary solid state materials. 相似文献