The construction of layered covalent carbon nitride polymers based on tri-s-triazine units has been achieved by using nucleobases (adenine, guanine, cytosine, thymine and uracil) and urea to establish a two-dimensional semiconducting structure that allows band-gap engineering applications. This biomolecule-derived binary carbon nitride polymer enables the generation of energized charge carrier with light-irradiation to induce photoredox reactions for stable hydrogen production and heterogeneous organosynthesis of C−O, C−C, C−N and N−N bonds, which may enrich discussion on chemical reactions in prebiotic conditions by taking account of the photoredox function of conjugated carbonitride semiconductors that have long been considered to be stable HCN-derived organic macromolecules in space. 相似文献
A new series of norcantharidin salt derivatives was designed and synthesized in good yield. The compounds structures were characterized by 1H‐NMR, 13C‐NMR, and IR spectra. These norcantharidin salts 5 exhibit good antitumor activity against both liver cancer and colon cancer cell lines in vitro, which seems to direct a right trend for the modification on cantharidin structure. 相似文献
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
Synthesis of natural products remains a daring task. Their richly diverse and intricate structures often encompass a large degree of unsaturation, contain fused and/or bridged rings, or possess numerous stereogenic centers. Thus, their preparation requires significant synthetic overhead, detracting from their overall practicality as well as hampering the ability of medicinal chemists to synthesize derivatives for pharmaceutical optimization and structure-activity relationship studies. The purpose of this Minireview is to showcase recent examples of efficient total syntheses. Emphasis was not given to the evaluation of ideality or economies (quality), but rather to the practicality (quality with quantity). 相似文献
Quantitative quadrupole mass spectrometry of (Ti, W)C-based cemented carbonitrides was carried out in order to monitor the
evolution of the gas species as a function of time and temperature during vacuum sintering. Solid standards and gas mixtures
as well as precise flow control were employed for calibration. Upon integration of the outgassing rates the carbon and nitrogen
evolutions and mass losses during sintering of raw hardmetal powder mixtures (WC, TiC,…) and cemented carbonitrides could
be quantified. Outgassing occurs in the range of temperatures 490–1480 °C. Nitrogen outgassing of (Ti, W)(C, N) was greater
than that of Ti(C, N) due to the presence of W which increases the nitrogen activity in the solid causing a higher nitrogen
equilibrium pressure. TiN showed a CO (0.2 wt%) and N2 (0.5 wt%) weight loss only in the presence of the binder phase. For powder mixtures, it was observed that the amount of CO,
CO2 and N2 liberated during vacuum sintering increased with the addition of cobalt in comparison with the same powders without binder
phase. Nitrogen containing cermet alloys showed a greater loss of carbon than (Ti, W)C-based hardmetals. A careful control
of carbon content by doping seems to be necessary in such alloys to avoid η-phase formation.
Received July 7, 2000. Revision December 4, 2000. 相似文献
Amorphous precursor nanopowders of zirconolite (CaZrTi2O7) were prepared using a water-in-oil micro-emulsion synthesis, with Ti(OiC3H7)4, Zr(OnC3H7)4 and either Ca(OC2H5)2 or an aqueous Ca(NO3)2 solution as precursors. The stoichiometry and structural evolution of the nanoparticles were investigated using a range of techniques, including ICP-MS, TEM, gas adsorption and vibrational spectroscopy. The use of Ca(OC2H5)2 led to slightly sub-stoichiometric nanopowders (CaxZrTi2O6+x, x = 0.8), following washing. Lower values of x were obtained in the washed nanopowders when using Ca(NO3)2, with x = 0.004, 0.022 or 0.52 at pH 2, 7 or 13, respectively. In the latter system, a comparison between the washed and unwashed nanopowders revealed that 25% of the calcium was lost during washing. The Ca(NO3)2 was found to form unstable tetraamine complexes within the reverse micelles at high pH, which transformed into Ca(OH)2 on ageing. The Ca(OH)2 can then interact with the hydrolysed titanium/zirconium alkoxides, and thus be integrated chemically into the final nanoparticle structure. 相似文献
A titanocene-ferrocenyl complex, （5-ferrocenyl-2-hydroxybenzenecarboxylato- O,O′）-bis（methylcyclopentadienyl）titanium（IV） 4, and an unexpected ionic complex, [C7H8NO3]- [（C5H5）Fe（C5H4）SO3]·H2O3 were synthesized and characterized by IR, ^1H NMR and elemental analysis. Compound 3 is of triclinic, space group P1 with a = 5.954（2）, b = 13.208（5）, c = 13.252（5） A, α = 60.993（7）,β = 84.342（8）,γ = 86.933（8）°, Z = 2, V = 906.8（6）A^3, Dc = 1.601 g/cm^3, μ（MoKα） = 0.987 mm^-1, F（000） = 452, the final R = 0.0647 and wR = 0.1333 for 2311 observed reflections （I 〉 2σ（I））. Compound 4 belongs to the monoclinic system, space group P2 1/c with α = 14.3310（9）, b = 12.5065（8）, c = 12.9406（10） A, β = 95.101（4）°, Z = 4, V = 2310.2（3） A^3, Dc = 1.513 g/cm^3, μ（MoKα） = 1.004 mm^-1, F（000） = 1088, the final R = 0.0461 and wR = 0.1048 for 2112 observed reflections （1 〉 2σ（I））. 相似文献
Caught in the middle : The ionomycin calcium complex (see structure; O red, Ca green) was the target of an approach featuring the efficient asymmetric synthesis of an allene by a copper(I)‐mediated anti‐selective SN2′ reaction, a highly stereoselective gold(III)‐catalyzed cycloisomerization of an α‐hydroxyallene, and a Rh‐catalyzed rearrangement of an α‐diazo‐β‐hydroxyketone.
The [RuNO(Thio)4Cl]Cl2 compound (where Thio is thiocarbamide) was synthesized by reacting nitrozochloro complexes of Ru with thiocarbamide. Its structure and properties in solutions were studied by IR, EAS, EPR, pH-metric, and electrical conductivity methods. The complex was found to have octahedral structure, with the chlorine atom in the trans-position relative to the nitrozo group, and four Thio groups coordinated through the sulfur atom and lying in the equatorial plane. This compound is labile in solutions. The mechanism and rate constants of the first hydrolysis stage were determined at 25, 50, and 75°C, and the enthalpy of the reaction was estimated. With a Thio excess, the nitrozo group is replaced to form the Ru(III) and Ru(II) thiocarbamide complexes. 相似文献
A nine-step (!) solid-phase synthesis and subsequent cleavage with cyclization from the polymeric support were the keys to preparing high-quality molecular libraries of thiazolylhydantoines 1 from modified amino acid building blocks. Each step in the synthesis is different. Because the final cyclization cleaves only molecules that have been successfully constructed, the products obtained are pure. R1, R2=alkyl; R3=aryl, arylO; R4=allyl. 相似文献
