A convenient and efficient preparation of Stryker's reagent, [Ph3PCuH]6, under homogeneous conditions using silanes as the reducing agent is detailed. The reaction time can be reduced to 1-2 h, and high yields of Stryker's reagent can be routinely achieved. The same method has been extended to the synthesis of [Ph3PCuD]6 using Ph2SiD2. 相似文献
The isomeric chlorosulfones 3, 4 and 5 are prepared by 1,4-addition of sulfonyl chlorides to isoprene, Dehydrohalogenation affords the corresponding 2- and 3-methylbutadienyl sulfones in a configuration which is dependent on the configuration of the chlorosulfone. Pure Z-2-methylbutadienyl sulfones 1 are obtained by displacement of primary halides by the Z-sulfinate anion 2. The Z-sulfones 1 are isomerized to E/Z-mixtures. The E/Z-mixtures are separated into their components and the configuration of the isomers is established by the NMR-NOE technique. 相似文献
Ultrathin epitaxial films of YBa2Cu3O7– on SrTiO3 prepared by Direct Current (DC) sputtering and pulsed laser deposition were imaged by Atomic Force Microscopy (AFM) to follow the different stages of growth of the thin films. Series of films with thicknesses between 1.2 nm and 12 nm (1–10 monolayers of YBa2Cu3O7–) were prepared under identical conditions, optimized with respect to electrical and structural properties, to obtain information on the mechanisms responsible for the formation of growth spirals which are commonly observed in films having a thickness of several 10 nm or more. It could be shown that few layers are formed by a layered growth mode where material is attached laterally to 2D islands which are only one c-axis unit cell in height. In a later stage of growth when about 8–10 layers have been formed, the growth process changes to a mode which is mediated by growth spirals. This could be directly monitored in the AFM images where different defect structures like vertically sheared growth fronts and dendrite-like terraces of stacked islands as well as the resulting growth spirals could be identified. 相似文献
In 1962 Erd\H{o}s proved that every real number may be decomposed into a sum of Liouville numbers. Here we consider more general functions which decompose elements from an arbitrary local field into Liouville numbers. Several examples and applications are given. As an illustration, we prove that for any real numbers , not equal to 0 or 1, there exist uncountably many Liouville numbers such that are all Liouville numbers.
Polyol Metal Complexes. 25. rac-Mannose, rac-Arabitol and L -Threitol as Deprotonated Ligands in Ferrates(III ) Ba2[Fe2(β-rac-ManfH?5)2] · 12H2O ( 1 ), Sr4[Fe4(rac-Arab1,2,3,5H?4)4(OH)2]CO3 · 33 H2O ( 2 ), and Ba2[Fe2(L-ThreH?4)2(OH)2] · 12.5 H2O ( 3 ) (Man = mannose, Arab = arabitol, Thre = threitol) have been crystallized from alkaline aqueous solution. Crystal structure analysis revealed dinuclear ferrate(III ) ions for 1 and 3 , the former being a Ci-symmetrical homoleptic ferric complex with pentadentate pentaanions derived from racemic β-mannofuranose. In 3 , besides tetradentate L -threitolato ligands, there is one terminal hydroxo ligand at each ferric center. Hydroxo ligands are also present in the Ci-symmetrical hexaanions of 2 , which are tetranuclear planar entities built up from four edge-sharing FeO6 octahedra. However arabitol is a pentitol, the tetraanionic ligands are only tetradentate for steric reasons. 相似文献
Hexafluorobut-2-yne reacts with dichlorocarbene [generated by thermal decomposition of the silane CC13SiF3] to give 3,3-dichlorobistrifluoromethyl- (I) and 1,3-dichlorobistrifluoromethyl-cyclopropene (II). The 3,3-dichloro-compound (I) is isomerised to (II) by heat, light, or chemical catalysis, but high yields of either pure cyclopropene may be obtained by modification of the reaction conditions. The cyclopropenium ion (III) is formed when either (I) or (II) is treated with antimony pentafluoride.Both (I) and (II) undergo free-radical addition of halogens, but the slow reaction of (II) with trifluoromethyl radicals gives a mixture of products. Nucleophilic substitution of chloride ion from both cyclopropenes occurs very readily, and with ethoxide ions both mono- and di-ethoxybistrifluoromethylcyclopropenes are obtained. The cyclopropenes also react with fluoride ion, iodide ion, or Grignard compounds. 相似文献
[reaction: see text] The combination of catalytic palladium(0) and Trost ligand provides an effective catalyst for the rearrangement of allyl beta-ketoesters. The mechanism of the transformation involves formation of pi-allyl palladium intermediates which undergo enantioselective attack by ketone enolates. Decarboxylation of beta-ketocarboxylates allows regiospecific generation of enolates under extremely mild conditions. 相似文献
The solid reaction products from pyrolysis of polyethylene terephthalate in the presence and absence of red phosphorus were characterized by CP/MAS 13C-NMR, FR-IR, and MAS 31P-NMR spectroscopy. Over the temperature range of 300–400°C, polyethylene terephthalate was converted in a sealed vial to a highly crosslinked polymer of terephthalic acid. Pyrolysis in the presence of red phosphorus, which functions as a flame retardant by increasing the amount of char, yielded an intractible polyaromatic phosphate ester. After thermal cleavage of polyethylene terephthalate with formation of free carboxyl and vinyl ester groups, there are two competing reaction pathways. The smaller molecular weight fragments may enter the vapor phase where they undergo further degradation primarily to CO2, CO, and acetaldehyde, as described by others. However, if volatilization of the oligomeric fragments is inhibited, an alternate reaction pathway gives rise to the formation of highly crosslinked char. Red phosphorus decreases the volatility of the oligomeric fragments by converting them to phosphates and thereby enhances char formation. 相似文献
Azomethine ylide 3 , generated by thermolysis of 3,4-diphenyl-Δ1-1,2,3-triazoline-5,5-dimethyldicarboxylate 1 , can be trapped by isonitriles to give 3-imino-1,4-diphenylazetidine-2,2-dimethyldicarboxylates 5 . The IR, 1H-NMR, 13C-NMR and mass spectral data of the new compounds are discussed. 相似文献
The synthesis of homochiral heterocyclic α-hydroxy acids starting from (S)- and (R)-malic acid using hexafluoroacetone as protecting and activating agent is described. The new compounds are useful building
blocks for peptide and depsipeptide modification. 相似文献