共查询到20条相似文献,搜索用时 31 毫秒
1.
《Journal of organometallic chemistry》1990,384(3):C53-C56
Whereas the addition of tributyl(trimethylgermyl)stannane to 1-alkynes in the presence of tetrakis(triphenylphosphine)palladium proceeds regiospecifically, the direction of its addition to allenes is dependent on the structure of the allene. 相似文献
2.
The reaction of aryl iodides with 1,1‐diphenyl‐silacyclobutane in the presence of a catalytic amount of Pd(PPh3)4 affords unexpected ring‐opening adducts, 1‐ and 2‐propenyl(triaryl)‐silanes, in good yields. On the other hand, the PdCl2(PhCN)2‐catalyzed reaction of 1,1‐diphenylsilacyclobutanes with aryl halides gives unexpected products, triarylsilanols, after hydrolysis in moderate yields. The catalysis involves the reaction of aryl–palladium intermediates with silacyclobutanes along with regioselective aryl–silicon bond formation. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
3.
[reaction: see text] The reactions of singlet oxygen with substrates containing both sulfide and olefinic linkages have been examined. The dramatic increase in sulfoxide formation in the interior of the zeolite in comparison to solution is attributed to zeolite stabilization of the persulfoxide intermediate and concomitant inhibition of physical quenching of singlet oxygen. 相似文献
4.
The bromination reaction of p-benzoquinone-fused norbornadiene was studied at various temperatures (?78, ?50, 0, 25, and 77 °C). At room temperature, the double bonds of the p-benzoquinone units were mainly brominated. The double bond of the norbornene unit also underwent a bromination reaction in a yield of only 2%. However, the reaction at ?78 °C resulted in the formation of products derived from the attack of bromine on the norbornene double bond with higher charge density. In contrast to the bromination reaction, the epoxidation reaction of the same compound with m-chloroperbenzoic acid and dimethyldioxirane exclusively resulted in the formation of products derived from the addition to the double bond of norbornadiene. The regioselectivity observed was investigated and the results were supported by theoretical calculations. 相似文献
5.
The density functional theory B3LYP/6-31G(d, p) method is employed to study the mechanism of aminolysis reaction of p-substituted phenyl acetates (CH3C(O)OC6H4X, X = H, NH2, and NO2) with ammonia in the gas phase. Two reaction pathways are considered: the concerted process and the stepwise pathway through neutral intermediates. The substituent effects of the leaving groups on the reactivity of phenyl acetates are discussed. The solvent effect of acetonitrile on the title reaction is also assessed by the polarizable continuum model (CPCM model) at B3LYP/6-31++G(d, p) level of theory. The calculated results show that the activation barriers of the concerted pathways are lower than those of the rate-controlling steps of the stepwise processes for all the three aminolysis reactions. This aminolysis of phenyl acetates is more favorable for X = NO2 than for X = H and NH2 in the gas phase and in acetonitrile. 相似文献
6.
Rajkumar GA Sandanayaka AS Ikeshita K Araki Y Furusho Y Takata T Ito O 《The journal of physical chemistry. B》2006,110(13):6516-6525
A rotaxane tethering both fullerene (C60) and ferrocene (Fc) moieties (abbreviated as (C60;Fc)rotax+) was synthesized in a good yield by the urethane end-capping of pseudorotaxane based on the crown ether-secondary amine motif. In (C60;Fc)rotax+, the C60 group serving as an electron acceptor is attached to the crown ether wheel, through which the axle with a Fc group acting as an electron donor on its end penetrates. The intrarotaxane photoinduced energy-transfer and electron-transfer processes between C60 and Fc in (C60;Fc)rotax+ have been investigated by time-resolved transient absorption and fluorescence measurements with changing solvent polarity. Nanosecond transient absorption measurements of the rotaxane demonstrated that the charge-separated state (C60*-;Fc*+)rotax+ is formed mainly via the excited triplet state of C60 in polar solvents. The lifetime of (C60*-;Fc*+)rotax+ was evaluated to be 20 ns in dimethylformamide (DMF) at room temperature. With lowing temperature, the lifetime of (C60*-;Fc*+)rotax+ extends to 270 ns in DMF at -65 degrees C, due to the structural changes leaving C60*- and Fc*+ at a relatively long distance in the low-temperature region. 相似文献
7.
Christian Pietsch Martin W. M. Fijten Hanneke M. L. Lambermont‐Thijs Richard Hoogenboom Ulrich S. Schubert 《Journal of polymer science. Part A, Polymer chemistry》2009,47(11):2811-2820
Homo‐ and copolymers of di(ethylene glycol) methyl ether methacrylate (DEGMA) and oligo(ethyleneglycol) methyl ether methacrylate (OEGMA1100) were synthesized with various chain lengths via reversible addition fragmentation chain transfer (RAFT) polymerization in ethanol using [M]/[RAFT] ratios of 100 and 200. Kinetic investigations on the homo‐ and copolymerization of these monomers were performed using a parallel synthesizer resulting in well‐defined polymers with polydispersity indices mostly below 1.3. The polymerization kinetics are presented and discussed in detail surprisingly revealing that the DEGMA homopolymerization is slower than the OEGMA1100 homopolymerization. Transfer coefficients c were estimated to be ~0.5 for the RAFT polymerization of both DEGMA and OEGMA1100 resulting in hybrid behavior at the beginning of the polymerizations. Subsequent copolymerization also revealed fast incorporation of the OEGMA1100 and relatively slow incorporation of DEGMA resulting in well‐defined copolymers with a molecular weight up to 100 kDa and polydispersities around 1.20. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2811–2820, 2009 相似文献
8.
Orazio A. Attanasi Lucia De Crescentini Paolino Filippone Samuele Lillini 《Tetrahedron letters》2007,48(14):2449-2451
New tetrahydro-3aH-cyclopenta[d][1,3]thiazolines and hexahydro-1,3-benzothiazolines were obtained in satisfactory yields by reaction of cycloalkenyl-1-diazenes with thioamides. These thiazolines were converted into unknown fused cycloalkyl-thiazoline-pyrazole systems. 相似文献
9.
Takashi Suzuki Katsumi Tanaka Isamu Toyoshima 《Reaction Kinetics and Catalysis Letters》1989,38(2):209-213
Active sites for ethylene homologation (3C2H42C3H6) and ethylene metathesis (C2H4–12C2+C2H4–13C22C2H4–13C1) were discriminated by adding platinum to a reduced molybdena silica catalyst, and the former was presumed to be composed of several molybdenum species, while the latter was presumed to be composed of one molybdenum species.
(3C2H42C3H6) (C2H4–12C2+C2H4–13C22C2H4–13C1) . , , .相似文献
10.
Different shapes of the plot rate vs. flow-rate can be obtained for ethylene hydrogenation on nickel. They relate to the presence of oxygen traces and the way they are introduced into the reacting mixture. A previous statement according to which active centers are produced by the conversion of oxygen into water is thus confirmed.
. . , . ., , .相似文献
11.
Kazuki Fukushima Daniel J. Coady Gavin O. Jones Hamid A. Almegren Abdullah M. Alabdulrahman Fares D. Alsewailem Hans W. Horn Julia E. Rice James L. Hedrick 《Journal of polymer science. Part A, Polymer chemistry》2013,51(7):1606-1611
This article describes studies on the catalytic activity of several nitrogen‐based organic catalysts for the depolymerization of poly(ethylene terephthalate) (PET), in which a few cyclic amidines work more effectively than a potent, bifunctional guanidine‐based catalyst 1,5,7‐triazabicyclo‐[4,4,0]‐dec‐5‐ene (TBD) in the presence of short chain diols that play a role in activation of carbonyl groups through hydrogen bonding. Further studies prove that the catalytic efficiency at the above specific conditions depends only on the extent of activation of a hydroxyl group rather than simply the pKa of the bases. For glycolysis with excess short‐chain alkanediols, 1,8‐diazabicyclo[5.4.0]undec‐7‐ene is the best catalyst. In contrast, TBD shows outstanding catalytic activity in depolymerizations of PET with mono‐alcohols and longer‐chain diols. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
12.
Ronald L. Bennett Michael I. Bruce F.Gordon A. Stone 《Journal of organometallic chemistry》1975,94(1):65-74
The interaction of azobenzene and MnR(CO)5 (R Me, Et, CH2Ph, CH2-C6Me5, COCF3, COCH2C6F5, COCH2OPh, Ph or C6F5) affords MPh)-(CO)4, together with a binuclear complex Mn2(CO)6(C12H10N2) in some cases. The metallation reaction is shown to proceed most readily with Mn-(CH2Ph)(CO)5; with this reagent, the metallated complexes MMe2)-(CO)3[PMe2(CH2Ph)] (two isomers) and MsMe2(CO)4 have been obtained on treatment with EMe2(CH2Ph) (E P and As, respectively). 相似文献
13.
Shigeru Kitano Issei Hisamitsu Yoshiyuki Koyama Kazunori Kataoka Teruo Okano Yasuhisa Sakurai 《先进技术聚合物》1991,2(5):261-264
A novel polymer complex system sensitive to glucose was studied as a candidate material for formulating a chemically regulated insulin release system. A ternary copolymer of N-vinyl-2-pyrrolidone (NVP), 3-acrylamidophenylboronic acid (AAm-PBA) and N,N-dimethylaminopropylacrylamide (DMAPAA) (poly(NVP-co-PBA-co-DMAPAA)) was synthesized by radical copolymerization. The phenylboronic acid group in this copolymer serves as a glucose sensor moiety. Poly(NVP-co-PBA-co-DMAPAA) was soluble in water in the pH range of 3–12, in sharp contrast to a binary copolymer of NVP and AAm-PBA (poly(NVP-co-PBA)) which showed solubility only under alkaline aqueous conditions, where the boronic acid group is in a tetrahedral ionized form. The protonated amino group in poly(NVP-co-PBA-DMAPAA) contributed to increase the solubility of the polymer under physiological and acidic aqueous conditions. Furthermore, poly(NVP-co-PBA-co-DMAPAA) formed a stable polymer complex gel with poly(vinyl alcohol) (PVA) in pH 7.4 phosphate buffered solution due to the formation of a covalent linkage between the boronic acid groups in ternary copolymer and diol units in PVA. The release of myoglobin as model protein from the complex gel was increased immediately after the addition of glucose, due to the transition of gel into sol state, indicating the feasibility of this complex gel as a candidate material for a glucose-responsive delivery system for insulin. 相似文献
14.
The stereochemistries observed for nucleophilic substitutions on optically active bromo- and thiophenyl-silanes are compared with those reported for Cl, F, OR and H leaving groups. They allow the completion of the previously proposed empirical order for the dependence of stereochemistry in the nature of the leaving group viz.; predominant stereochemistry: IN → RN; ease of substitution: Br ? Cl ? SR ? F ? OMe > H. 相似文献
15.
This paper describes the emission spectroscopic investigation of singlet and triplet excimers of tethered bisnaphthalene species at room temperature. 1,1'-Dinaphthylethane (DNE) and 1,1'-dinaphthylpropane (DNP) were incorporated into a 3-D network of a 1.3 nm diameter pseudo-spherical supercage of zeolites Y (with an entry aperture of 0.74 nm), and a 1-D channel of zeolite L with a 0.71 nm aperture. In the straight channel of zeolite L, DNP adopts a parallel-sandwich conformation as suggested by the observation of entirely excimeric fluorescence, while DNE can only enter the channel in an open form. As a result, incorporation of DNP into zeolite L exchanged with Tl(+) ions, which induce enhanced intersystem-crossing, allowed the observation of a broad and featureless phosphorescence spectrum that is ascribable to the triplet excimer of DNP. In contrast, an entirely monomeric phosphorescence is observed for DNE. Furthermore, we observed a monomeric phosphorescence spectrum for DNP in Tl(+)-exchanged zeolite Y, in which DNP was shown to assume its open conformation. Thus the parallel-sandwich structure is responsible for the triplet excimer of the bisnaphthalene species as well as for the singlet counterpart. The parallel-sandwich conformation of the triplet excimer of DNP immobilized by the host framework is significantly different from the previously proposed L-shaped configuration in solution. However, it is very similar to that of the triplet excimer of triple-tethered carbazolophane, as revealed quite recently by Ohkita's group (J. Phys. Chem. B, 2007, 111, 10905). Thus the present study helps tackle the long-term issue of triplet excimer through the use of zeolites. 相似文献
16.
N. L. Pechnikova A. V. Lyubimtsev S. A. Syrbu T. A. Ageeva A. S. Semeikin 《Russian Journal of General Chemistry》2013,83(1):99-105
The mono-meso-allyloxy- and acrylamidophenylporphyrins were synthesized from the corresponding hydroxy- and aminophenylporphyrins. All the compounds were characterized by IR, UV-Vis, 1H NMR and mass spectra. 相似文献
17.
The effect of leaving groups on the reactivity of 3-X-2-nitrothiophene (1), 2-X-3-nitrothiophene (II) and 2-X-5-nitrothiophene (III) (X = Cl, Br, I, OC6H4NO2(p), SO2C6 H5) with sodium thiophenoxide has been examined. The results show that the reactivity ratio kIII/kII is always greater than unity and is relatively uninfluenced by changing leaving groups compared to the ratio kI/kII. The ratio kI/kII is greater or smaller than unity, according to following patterns of leaving groups Examination of the reactivity of the three series of compounds having Cl, Br, I and C6H4NO2(p) as leaving groups showed the absence of an “element effect” which indicates that in the transition states of these displacement reactions there is little breaking of the bond to the group being displaced. 相似文献
18.
Fujita S 《Journal of chemical information and computer sciences》2004,44(5):1719-1726
The hierarchy of point groups, RS-stereoisomeric groups, stereoisomeric groups, and isoskeletal groups is discussed to comprehend the chirality, RS-stereogenicity, stereogenicity, and isoskeletal isomerism for ethylene derivatives. The RS-stereoisomeric groups for ethylene derivatives have been clarified not to coincide with their stereoisomeric groups, so that diastereomers (E/Z-isomers) are not identical with RS-diastereomers. To discuss the relationship among RS-diastereomers, m-diastereomers, and isoskeletal isomers, we have proposed the concepts of extended stereoisograms and extended stereoisogram sets, where the term "m-diastereomers" is coined to show its difference from the traditional term "diastereomer". Thereby, ethylene derivatives are classified into Types II-II/II-II/II-II, IV-IV/IV-IV/IV-IV, etc. on the basis of relevant stereoisograms (Types I to V). The stereoisomerism of ethylenes has been concluded to be treated in terms of m-diastereomers characterized by the E/Z-nomenclature but not to be treated in terms of RS-diastereomers characterized by the RS-nomenclaure. 相似文献
19.
Kota Miyata Satoru Yasuda Takuto Masuya Satoshi Ito Yusuke Kinoshita Hitoshi Tamiaki Toru Oba 《Tetrahedron》2018,74(27):3707-3711
Iodination of protoporphyrin IX dimethyl ester using phenyliodine bis(trifluoroacetate) (PIFA) and I2 was studied. Iodine added to both the C3- and C8-vinyl groups equally to afford the iodohydrin or iodoether in the presence of water or alcohol, respectively. Any meso-hydrogen atom was not substituted by an iodine atom under these conditions, although both the vinyl group and one of the meso positions of methyl pyropheophorbide-a bearing a chlorin π-system, a chlorophyll-a derivative, was modified with PIFA and I2. The reaction intermediates derived from the porphyrin were more reactive than those from the chlorin and liable to form intermolecular linkages. The obtained 2-iodo-1-hydroxyethyl group was transformed into a formyl group by a mild treatment. The corresponding iodoether moiety was readily converted into the acetyl group under basic conditions. These transformations were also applicable to smaller olefins such as styrene. 相似文献
20.
A one-pot procedure for the synthesis of polyethylene tethered on multi-walled carbon nanotubes by in situ ethylene copolymerization with an olefin-type comonomer, α-alkene functionalized multi-walled carbon nanotubes (MW - CH = CH2) is reported. The covalent linkage between polyethylene and multi-walled carbon nanotubes is demonstrated. The MWCNTs are chemically oxidized first by a strong oxidizing agent and then functionalized with chlorocarbonyl groups (MW-COCl) via reacting with thionyl chloride. The MW-CH=CH2 are obtained by esterification of ω-undecylenyl alcohol with MW-COCl. The MW-CH=CH2 may serve as olefin-type comonomers to further synthesize core-shell structured copolymers with a multi-walled carbon nanotubes core grafted with side chains of polyethylene via rac-(en)(THInd)2ZrCl2 copolymerization catalyst. The core-shell structured nanocomposites were characterized by means of 1H-NMR, SEM, FTIR and TGA. The results confirmed the formation of polyethylene chains growing from the surface of multi-walled carbon nanotubes. 相似文献