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81.
Stupi BP Li H Wang J Wu W Morris SE Litosh VA Muniz J Hersh MN Metzker ML 《Angewandte Chemie (International ed. in English)》2012,51(7):1724-1727
82.
An alternative synthesis of C‐monoacetylenic phosphaalkenes trans‐Mes*P=C(Me)(C≡CR) (Mes* = 2, 4, 6‐tBu3Ph, R = Ph, SiMe3) from C‐bromophosphaalkenes cis‐Mes*P=C(Me)Br using standard Sonogashira coupling conditions is described. Crystallographic studies confirm cis‐trans isomerization of the P=C double bond during Pd‐catalyzed cross coupling, leading exclusively to trans‐acetylenic phosphaalkenes. Crystallographic studies of all synthesized compounds reveal the extend of π‐conjugation over the acetylene and P=C π‐systems. 相似文献
83.
González-Toro DC Ryu JH Chacko RT Zhuang J Thayumanavan S 《Journal of the American Chemical Society》2012,134(16):6964-6967
Supramolecular nanoassemblies, which are capable of binding and delivering either lipophilic small molecules or hydrophilic molecules, are of great interest. Concurrently binding and delivering this combination of molecules is cumbersome, because of the opposing supramolecular host requirements. We describe the development of a versatile nanoassembly system that is capable of binding and delivering both, a protein and a lipophilic small molecule, simultaneously inside the cells. 相似文献
84.
We demonstrate laser induced semiconductor–metal transition through an abrupt change in diamagnetic susceptibility of a donor at critical concentration in a GaAs/AlxGa1−xAs Quantum Well for finite barrier model in the effective mass approximation using variational principle. We have considered Anderson‘s localization due to the random distribution of impurities in our calculation. The nonparabolicity of the conduction band is also considered. Our results without laser field agree with the earlier theoretical results and also with the recent experimental results. 相似文献
85.
The substituted thiourea, 4‐methyl‐3‐thiosemicarbazide, was oxidized by iodate in acidic medium. In high acid concentrations and in stoichiometric excess of iodate, the reaction displays an induction period followed by the formation of aqueous iodine. In stoichiometric excess of methylthiosemicarbazide and high acid concentration, the reaction shows a transient formation of aqueous iodine. The stoichiometry of the reaction is: 4IO + 3CH3NHC(S)NHNH2 + 3H2O → 4I− + 3SO + 3CH3NHC(O)NHNH2 + 6H+ (A). Iodine formation is due to the Dushman reaction that produces iodine from iodide formed from the reduction of iodate: IO + 5I− + 6H+ → 3I2(aq) + 3H2O (B). Transient iodine formation is due to the efficient acid catalysis of the Dushman reaction. The iodine produced in process B is consumed by the methylthiosemicarbazide substrate. The direct reaction of iodine and methylthiosemicarbazide was also studied. It has a stoichiometry of 4I2(aq) + CH3NHC(S)NHNH2 + 5H2O → 8I− + SO + CH3NHC(O)NHNH2 + 10H+ (C). The reaction exhibits autoinhibition by iodide and acid. Inhibition by I− is due to the formation of the triiodide species, I, and inhibition by acid is due to the protonation of the sulfur center that deactivates it to further electrophilic attack. In excess iodate conditions, the stoichiometry of the reaction is 8IO + 5CH3NHC(S)NHNH2 + H2O → 4I2 + 5SO + 5CH3NHC(O)NHNH2 + 2H+ (D) that is a linear combination of processes A and B. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 193–203, 2000 相似文献
86.
87.
The oxidative addition of aromatic and benzylic halides to activated metallic nickel occurred under mild conditions to give the corresponding dehalogenative coupled products in good yields. 相似文献
88.
Treatment of a vinyl chloride with commercially available aqueous sodium hypochlorite solution in a 2:5 mixture of acetic acid/acetone at 0 degrees C for about 1 h cleanly leads to the corresponding alpha-chloroketone. Similarly, if a vinyl bromide is exposed to sodium hypobromite (freshly prepared from bromine and sodium hydroxide) at 0 degrees C in 2:5 acetic acid/acetone as solvent, an alpha-bromoketone is produced. This methodology has been applied to a number of vinyl chlorides and vinyl bromides, and the transformations generally proceed in high yields. The mild reaction conditions are compatible with a variety of functional groups including amides, esters, and imines. 相似文献
89.
Lithium stannides were prepared from lithium naphthalenide and tin (II) chloride or tin (0) powder in THF solvent at room temperature under dry argon atmosphere. They were characterized with elemental analysis, XRD, and solid 6,7Li NMR. Stabilities and reactivities of lithium stannides prepared from different conditions were tested and showed they were stable for a limited time at low temperatures. Best reactivity was obtained when they were prepared from tin (II) chloride and an excess of lithium naphthalenide. The lithium stannide mixture can reductively cleave carbon-halogen bonds and yield pinacol coupling with aldehydes. Organolithium compounds prepared from lithium stannides and organic halides add to ketones or aldehydes under Barbier conditions. 相似文献
90.
Manoso AS Ahn C Soheili A Handy CJ Correia R Seganish WM Deshong P 《The Journal of organic chemistry》2004,69(24):8305-8314
General reaction conditions for the synthesis of aryl(trialkoxy)silanes from aryl Grignard and lithium reagents and tetraalkyl orthosilicates (Si(OR)(4)) have been developed. Ortho-, meta-, and para-substituted bromoarenes underwent efficient metalation and silylation at low temperature to provide aryl siloxanes. Mixed results were obtained with heteroaromatic substrates: 3-bromothiophene, 3-bromo-4-methoxypyridine, 5-bromoindole, and N-methyl-5-bromoindole underwent silylation in good yield, whereas a low yield of siloxane was obtained from 2-bromofuran, and 2-bromopyridine failed to give silylated product. The synthesis of siloxanes via organolithium and magnesium reagents was limited by the formation of di- and triarylated silanes (Ar(2)Si(OR)(2) and Ar(3)SiOR, respectively) and dehalogenated (Ar-H) byproducts. Silylation at low temperature gave predominantly monoaryl siloxanes, without requiring a large excess of the electrophile. Optimal reaction conditions for the synthesis of siloxanes from aryl Grignard reagents entailed addition of arylmagnesium reagents to 3 equiv of tetraethyl- or tetramethyl orthosilicate at -30 degrees C in THF. Aryllithium species were silylated using 1.5 equiv of tetraethyl- or tetramethyl orthosilicate at -78 degrees C in ether. 相似文献