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181.
A novel protocol for intramolecular ketyl-olefin radical cyclization with low-valent titanium reagent is outlined. It allows the formation of the benzopyran nucleus from ortho-allyloxy propiophenones as the sole product in moderate yields via intramolecular radical cyclization. 相似文献
182.
An efficient and convenient conversion of aldoximes and ketoximes to the corresponding carbonyl compounds with tetrameric DABCO–bromine complex is reported. 相似文献
183.
An efficient method for the oxidation of alcohols is presented. The use of catalytic amounts of sodium chloride in combination with oxone allows the conversion primary aliphatic alcohols to symmetric esters. Secondary alcohols can be easily oxidized to ketones, and benzylic alcohols are converted to the corresponding aldehydes. The method is cost effective and enviromentally benign. 相似文献
184.
185.
The synthesis and characterisation of some new 1,5-benzodiazepines prepared from 4,6-diacetylresorcinol is reported. 相似文献
186.
Insun Park Kirill Efimenko Johan Sjöblom 《Journal of Dispersion Science and Technology》2013,34(3):318-327
We have developed a simple, robust, and efficient technology utilizing cheap and recoverable materials based on commercially available silicone elastomer networks for removing organic solvents and crude oil from waters. Hydrophobic and oleophilic properties of silicone elastomers endow poly(dimethyl siloxane) (PDMS) with the capacity to absorb a large variety of organics, including benzene (B), toluene (T), ethylbenzene (E), and xylene (X), commonly referred to as BTEX, and also crude oils, while at the same time enabling the organic “sponges” to float on waters, which facilitates straightforward handling. We developed a method for generating PDMS particles with variable sizes (ranging from hundreds nanometers to few millimeters) by drop-wise depositing siloxane/cross-linker mixtures into warm water, a process which leads to the cross-linking of the PDMS components. We have tested the capability of the PDMS particles to remove toluene and benzene from water. We also performed similar experiments by utilizing PDMS sheets. In both instances we observed a rapid sorption of the organic phase into PDMS; the amount of absorbed organic solvent depended on the concentration in water and the total mass (volume) of PDMS and did not depend on the geometry of the PDMS “sponge.” In addition, we have examined the uptake of toluene and benzene from toluene/benzene (T/B) mixtures dissolved in water. Our results indicate that the amount of benzene absorbed from the T/B mixtures into PDMS increases relative to the uptake from pure benzene/water solutions. This behavior is associated with toluene acting as a “surfactant” that effectively replaces the more unfavorable PDMS/B contacts with less costly T/B ones. Finally, a simple experiment demonstrates qualitatively that PDMS is also capable of removing crude oils from oil-contaminated waters. 相似文献
187.
Benjamin R. M. Lake Dr. Charlotte E. Willans 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(49):16780-16790
The preparation of a series of imidazolium salts bearing N‐allyl substituents, and a range of substituents on the second nitrogen atom that have varying electronic and steric properties, is reported. The ligands have been coordinated to a copper(I) centre and the resulting copper(I)–NHC (NHC=N‐heterocyclic carbene) complexes have been thoroughly examined, both in solution and in the solid‐state. The solid‐state structures are highly diverse and exhibit a range of unusual geometries and cuprophilic interactions. The first structurally characterised copper(I)–NHC complex containing a copper(I)–alkene interaction is reported. An N‐pyridyl substituent, which forms a dative bond with the copper(I) centre, stabilises an interaction between the metal centre and the allyl substituent of a neighbouring ligand, to form a 1D coordination polymer. The stabilisation is attributed to the pyridyl substituent increasing the electron density at the copper(I) centre, and thus enhancing the metal(d)‐to‐alkene(π*) back‐bonding. In addition, components other than charge transfer appear to have a role in copper(I)–alkene stabilisation because further increases in the Lewis basicity of the ligand disfavours copper(I)–alkene binding. 相似文献
188.
189.
Prof. Dr. Yoshihiko Yamamoto Shota Mori Dr. Masatoshi Shibuya 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(36):12034-12041
The transfer‐hydrogenative cyclization of 1,6‐diynes with Hantzsch 1,4‐dihydropyridine as a H2 surrogate was performed in the presence of a cationic ruthenium catalyst of the type [Cp′Ru(MeCN)3PF6]. Exocyclic 1,3‐dienes or their 1,4‐hydrogenation products, cycloalkenes, were selectively obtained, depending on the substrate structure and the reaction conditions. 相似文献
190.
Lóren C.C. Gonçalves Francine N. Victória David B. Lima Pedro M.Y. Borba Gelson Perin Lucielli Savegnago Eder J. Lenardão 《Tetrahedron letters》2014
(E)-1,2-Bis-chalcogen alkenes were stereoselectively prepared in good yields by the addition of diorganyl dichalcogenides to terminal alkynes using CuI/Zn/glycerol as a recyclable catalytic system. The antioxidant activity in vitro of four (E)-1,2-bis-chalcogen alkenes synthesized was evaluated and (E)-1,2-bis-(4-methoxyphenylselanyl)styrene 3b presented excellent activity. The catalytic system used in the synthesis was recovered and used directly up to 5 cycles without loss of activity. 相似文献