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91.
Zheng T Narayan RS Schomaker JM Borhan B 《Journal of the American Chemical Society》2005,127(19):6946-6947
A simple and efficient process to cyclize triols containing a 1,2-diol functionality with a pendant hydroxyl group is presented. The one-pot procedure converts the 1,2-diol into an ortho ester in situ, which upon treatment with a Lewis acid generates a cyclic acetoxonium intermediate. This intermediate is subsequently trapped by the pendant hydroxyl group to generate a cyclic ether. The stereochemistry of the 1,2-diol is transferred to the product with complete fidelity (inversion at the site of cyclization), and the reaction proceeds with high regioselectivity. The process is akin to the Lewis acid-catalyzed intramolecular ring-opening of epoxides with hydroxyl groups yielding cyclic ethers of various sizes with regio- and stereochemical control. 相似文献
92.
93.
Alumina supported ammonium fluoride was found as an efficient reagent for the synthesis of 1,2,4‐oxadi‐azoles of amidoximes under solvent free conditions using microwave irradiation. This method is a one‐pot, easy, rapid, and high‐yielding reaction for the synthesis of 1,2,4‐oxadiazole derivatives from amidoximes and acyl chlorides. Reaction of amidoximes with acylchlorides in the presence of alumina without ammonium fluoride gave only the corresponding O‐acylamidoximes as major product. 相似文献
94.
H. Michael Mack Everette A. Davis Babak Kadkhodayan Richard A. Taylor Dean C. Duncan Charles F. Beam 《Journal of heterocyclic chemistry》1987,24(6):1733-1739
C(α),O-Dilithiooximes, C(α),N-dilithiobenzoylhydrazones, or C(α),N-dilithiocarboalkoxyhydrazones were prepared in an excess of lithium diisopropylamide (LDA) and condensed with 2-aminobenzophenones, or isatoic anhydrides to give intermediates that were treated with aqueous acid, which caused their hydrolysis, cyclodehydration and/or linear dehydration to give products which were substituted quinolines or related fused-ring heterocycles (e.g., cycloheptaquinolines). Dilithiobenzoylacetone was condensed with 2-aminobenzophenones, which was followed by acid cyclodehydration to substituted 2-phenacylquinolines. 相似文献
95.
The reduction of 4‐nitrophenol and 2‐nitroaniline by palladium catalyst based on a KCC‐1/IL in aqueous solution
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Sakineh Esfandiari Baghbamidi Asadollah Hassankhani Esmael Sanchooli Seyed Mohsen Sadeghzadeh 《应用有机金属化学》2018,32(4)
KCC‐1/IL/Pd NPs can used as an excellent support for the synthesis of highly sparse homogeneous catalyst. KCC‐1 has high surface area that was functionalized with ionic liquid phase acting as the strong performers so that the Pd catalyst was well‐dispersed without aggregation on the framework of the KCC‐1/IL. This nano catalyst was specified by TGA, XRD, TEM, SEM, FT‐IR, and ICP. For reduction of 2‐nitroaniline and 4‐nitrophenol used from the KCC‐1/IL/Pd NPs as a green catalyst that showed excellent catalytic activities. Compared with the traditional substrate, KCC‐1 substantially increases protection and the accessibility of the nanoparticle sites due to its three dimensional hierarchical structure. 相似文献
96.
Stability and rheological properties of concentrated emulsions (including those for manufacture of vitamin microcapsules) can be related to elementary coalescence acts and adhesion of emulsion drops interacting through thin layers (microscopic emulsion films) of a dispersion medium A new procedure was used for measuring the adhesion force fa between two drops of n-heptane in polymer solutions and lifetime τ of the drops in the contacts depending on the volume concentration C of the polymer, time of formation tf of adsorption layers, temperature T, capillary pressure Pc in the film, surface area S of the film, and on addition of acetone and tannin. The molecular mechanism of the interaction between adsorption layers of polymers and of the process of film destruction is discussed on the basis of the relationships obtained for interaction free energy Δ Fa, activation energy E, destruction activation volume δ and physico-chemical parameters. 相似文献
97.
A series of 37 peptides containing an iodo-aryl amide active site were generated by means of both solid phase and conventional synthesis. These peptides were screened for asymmetric induction in the bromolactonization of 4-phenyl-4-pentenoic acid based on the generation of chiral bromoiodinane bromenium sources. The study culminated in the discovery of a tri-peptide iodo-aryl amide that effected the desired bromolactonization in quantitative conversion with 24% ee. The experiments disclosed herein provided valuable insight that ultimately facilitated the development of more synthetically useful enantioselective halocyclization methodology. 相似文献
98.
An optimized content delivery approach based on demand–supply theory in disruption-tolerant networks
Telecommunication Systems - Disruption-tolerance networks (DTNs) are suitable for applications that may lack continuous network connectivity. Examples of such applications include coupon... 相似文献
99.
Babak Kaboudin Foad Kazemi Abolfazl Ghaderian Zahra Zand 《Journal of the Iranian Chemical Society》2014,11(4):1121-1127
100.
A highly efficient photocatalytic reduction of nitroarenes using TiO2/polyethylene glycol 400-water (TiO2/PEG–H2O) is reported. This system at deoxygenated and illuminated (sunlight or violet LED) conditions efficiently reduced nitroarenes using oxalic acid or ammonium formate as a sacrificial electron donor. Reducible functional groups such as chloro, hydroxy, flouro, bromo and carbonyl were intact under the optimized reaction conditions. The 0.1 and 0.5–1 mmol amount of nitroarenes was used under sunlight and violet LED (400 nm) irradiation, respectively. Reusability of the nanotitania was successfully carried out four times. The analyses of the recovered catalyst after five runs including TEM, XRD, TGA and CHN were done and results showed that PEG is located on TiO2; no change in morphology, crystallinity and particle sizes was observed. 相似文献