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971.
Xiang‐Shan Wang Jian‐Rong Wu Jie Zhou Mei‐Mei Zhang 《Journal of heterocyclic chemistry》2011,48(5):1056-1060
Controlling the pH value by changing the negative ion of ionic liquids, the same reactions of aromatic aldehyde, 2‐(2,3‐dihydrothiochromen‐4‐ylidene) malononitrile and malononitrile product unaromatized and aromatized 6H‐benzo[c]thiochromene derivatives in high yields. The nice features of these procedures include mild reactions condition, simple operations, high yields, and environmentally benign. J. Heterocyclic Chem., (2011). 相似文献
972.
Two 1-D selenidoindates {[M(phen)(3)]In(2)Se(5)·H(2)O}(n) (M = Ni, Fe) were synthesized by a solvothermal method. The 1-D {[In(2)Se(5)](2-)}(n) anion is a new type of single 1-D structure constituted by an alternately fused four-membered In(2)Se(2) ring and five-membered In(2)Se(3) ring. The chalcogenoindates were separated as mechanical racemic mixtures of single enantiomer crystals, in which the R-helix of 1-D InSe anion is directed by the related clockwise (Δ) cations of [M(phen)(3)](2+) or the L-helix of 1-D anion is directed by the related anticlockwise (Λ) cation. The π···π, C···Se, and C-H···Se oriented interactions of metal complex cations with selenidoindate anions play an important role in the formation of the chiral crystals. The embedded [M(phen)(3)](2+) cations improve the optical absorption of the 1-D semiconductor materials. 相似文献
973.
Ab initio quantum mechanical/molecular mechanical method is combined with the polarized protein-specific charge to study the chemical reactions catalyzed by protein enzymes. Significant improvement in the accuracy and efficiency of free-energy simulation is demonstrated by calculating the free-energy profile of the primary proton transfer reaction in triosephosphate isomerase. Quantitative agreement with experimental results is achieved. Our simulation results indicate that electronic polarization makes important contribution to enzyme catalysis by lowering the energy barrier by as much as 3 kcal/mol. 相似文献
974.
Two nanotubular metal-organic frameworks (MOFs), {Cu(L1)·2H(2)O·1.5DMF}(∞) (1) and {Cu(2)(L2)(2)(H(2)O)(2)·7H(2)O·3DMF}(∞) (2), with novel topologies have been constructed based on Cu(2+), 5-(pyridin-4-yl)isophthalic acid (L1) and 5-(pyridin-3-yl)isophthalic acid (L2), respectively. Two MOFs were characterized by IR spectroscopy, thermogravimetry, single-crystal, and powder X-ray diffraction methods. Network analysis reveals a two-nodal (3,6)-connected (4·6(2))(2)(4(2)·6(10)·8(3)) net and a three-nodal (3,4)-connected (4·8(2))(4)(4(2)·8(2)·10(2))(2)(8(4)·12(2)) net. Interpenetration is inherently prevented by both of the topologies of the frameworks. The porosity of MOF 1 was confirmed by N(2) and CO(2) gas adsorption investigations. MOF 1 exhibits remarkable hydrogen sorption hysteresis at low pressure and a H(2) uptake capacity of 1.05 wt% at 77 K and 1 atm. 相似文献
975.
An efficient strategy for the total synthesis of (+)-przewalskin B is reported. The key steps feature an intermolecular S(N)2' substitution of iodoallylic phosphate with organocupper reagent, a diastereoselective organocatalytic aldol cyclization, as well as a Rh(2)(OAc)(4)-mediated intramolecular carbene insertion to the tertiary C-H bond. 相似文献
976.
Liu XK Qiu S Xiang YG Ruan YP Zheng X Huang PQ 《The Journal of organic chemistry》2011,76(12):4952-4963
The SmI(2)-mediated radical coupling reactions of β-hydroxylated pyrrolidine/piperidine aza-hemiacetals 8 and 9 and N,S-acetals 6 and 33 with α,β-unsaturated compounds are described. This method allows a rapid access to β-hydroxylated pyrrolidines, piperidines, pyrrolizidinones, and indolizidinones. Starting from N,S-acetal 33 and via a common intermediate 27, the alkaloids hyacinthacine A(2) (2), uniflorine A (3, 6-epi-casuarine), and the unnatural epimer 7-epi-casuarine (37) have been synthesized in four and five steps with overall yields of 34%, 16%, and 13%, respectively. The radical mechanism of the coupling reactions has been confirmed by controlled experiments, which also allowed deducing the anionic mechanism in the coupling between N,S-acetal 6 and carbonyl compounds. This demonstrates that the mechanisms of these SmI(2)-mediated reactions are switchable from Barbier-type anionic to radical by cooperative action of BF(3)·OEt(2) and t-BuOH. 相似文献
977.
Ibarra IA Yang S Lin X Blake AJ Rizkallah PJ Nowell H Allan DR Champness NR Hubberstey P Schröder M 《Chemical communications (Cambridge, England)》2011,47(29):8304-8306
The metal-organic frameworks NOTT-400 and NOTT-401, based on a binuclear [Sc(2)(μ(2)-OH)(O(2)CR)(4)] building block, have been synthesised and characterised; the desolvated framework NOTT-401a shows a BET surface area of 1514 m(2) g(-1) with a total H(2) uptake of 4.44 wt% at 77 K and 20 bar. 相似文献
978.
Xiang Y Qian X Chen Y Zhang Y Chai Y Yuan R 《Chemical communications (Cambridge, England)》2011,47(7):2080-2082
Reagentless, sensitive and multiplexed analysis of gyrB and K-ras gene biomarkers is achieved based on the proximity changes of two different redox-tags to the electrode surface upon DNA hybridizations, and the presence of the two gene biomarkers also acts as inputs and activates the logic gate. 相似文献
979.
TiO(2) films composed of flower-like TiO(2) microspheres with exposed {001} facets were synthesized by a simple one-pot hydrothermal method and exhibited tunable photocatalytic selectivity towards decomposition of azo dyes in water by modifying the surface of TiO(2) microspheres as well as by varying the degree of etching of {001} facets. 相似文献
980.