共查询到20条相似文献,搜索用时 31 毫秒
1.
The addition of s-butyllithium and t-butyllithium to trans-cyclooctene has been shown to occur very readily. The facile elimination of lithium hydride from s-cyclooctyllithium compounds affording cyclooctenes is also reported. 相似文献
2.
Quantum mechanical calculations indicate that the most stable conformation for 1,3-cycloheptadiene is a Cs semi-planar form, for trans-cyclooctene a C2 twist form and for cis-cyclooctene a form without symmetry. An equilibrium between two C1 forms and the Cs form can be suggested as a consequence of the negligible rotational barrier in 1,3-cycloheptadiene; no obviously preferred conformations exist in cis-cyclooctene, where the molecule is quite flexible. Theoretical results are consistent with the experimental data available. 相似文献
3.
Boyd's iterative force-field computer program, with modified parameters, has been used to calculate strain energies in the following molecules: trans-cyclooctene, cyclohexene, melhylenecyclohexane, 1,3,5- and 1,3,6-cyclooctatriene, and cyclononyne. Both static and dynamic aspects of the conformational properties of these molecules have been investigated in detail, and the results are discussed in conjunction with extant experimental data and previous force-field calculations. 相似文献
4.
The 1,2,3-oxadiazolidines resulting from the addition of 4,4′-dicyano-azoxybenzene to trans-cyclooctene or cis, trans-cycloocta-1,5-diene are not stable, bu suffer 1,3-dipolar cycloreversion to give an azomethine imine; this intermediate is either captured by a second molecule of the strained cycloalkene to give 1:2 adducts in high yields or it tautomerizes to an enehydrazine. 4,4′-Dinitroazoxybenzene and benzo[c]cinnoline N-oxide react analogously. 相似文献
5.
Günter Haufe Manfred Mühlstädt Dr. Jürgen Graefe 《Monatshefte für Chemie / Chemical Monthly》1977,108(4):803-811
In addition totrans-2-bromocyclooctanol andtrans-1,2-dibromocyclooctane,cis-4-bromocyclooctanol,cis-1,4-dibromocyclooctane,trans-1,4-dibromocyclooctane, and (Z)-5-bromocyclooctene are obtained, when (Z)-cyclooctene is treated with N-bromosuccinimide in the presence of water. Similarly the methoxybromination of (Z)-cyclooctene gives transanular products. 相似文献
6.
Edmund J Keliher Thomas Reiner Greg M Thurber Rabi Upadhyay Ralph Weissleder 《ChemistryOpen》2012,1(4):177-183
A number of exendin derivatives have been developed to target glucagon-like peptide 1 (GLP-1) receptors on beta cells in vivo. Modifications of exendin analogues have been shown to have significant effects on pharmacokinetics and, as such, have been used to develop a variety of therapeutic compounds. Here, we show that an exendin-4, modified at position 12 with a cysteine conjugated to a tetrazine, can be labeled with 18F-trans-cyclooctene and converted into a PET imaging agent at high yields and with good selectivity. The agent accumulates in beta cells in vivo and has sufficiently high accumulation in mouse models of insulinomas to enable in vivo imaging. 相似文献
7.
Keld L. Bak Aage E. Hansen Kenneth Ruud Trygve Helgaker Jeppe Olsen Poul Jørgensen 《Theoretical chemistry accounts》1995,90(5-6):441-458
Summary The second-quantization magnetic dipole operator that arises when London atomic orbitals are used as basis functions is derived. In atomic units, the magnetic dipole operator is defined as the negative of the first derivative of the electronic Hamiltonian containing the interaction with the external magnetic field. It is shown that for finite basis sets, the gauge origin dependence of the resulting magnetic dipole operator is analogous to that of the exact operator, and that the derived operator converges to the exact operator in the limit of a complete basis set. It is also demonstrated that the length expression for the rotatory strength in linear response calculations gives gauge-origin-independent results. Sample calculations ontrans-cyclooctene and its fragments are presented. Compared to conventional orbitals, the basis set convergence of the rotatory strengths calculated in the length form using London atomic orbitals is favourable. The rotatory strength calculated fortrans-cyclooctene agrees nicely with the corresponding experimental circular dichroism spectrum, but the spectra for the fragment molecules show little resemblance with that oftrans-cyclooctene.Dedicated to Prof. Jan Linderberg 相似文献
8.
The pretargeting strategy has recently emerged in order to overcome the limitations of direct targeting, mainly in the field of radioimmunotherapy (RIT). This strategy is directly dependent on chemical reactions, namely bioorthogonal reactions, which have been developed for their ability to occur under physiological conditions. The Staudinger ligation, the copper catalyzed azide-alkyne cycloaddition (CuAAC) and the strain-promoted [3 + 2] azide–alkyne cycloaddition (SPAAC) were the first bioorthogonal reactions introduced in the literature. However, due to their incomplete biocompatibility and slow kinetics, the inverse-electron demand Diels-Alder (IEDDA) reaction was advanced in 2008 by Blackman et al. as an optimal bioorthogonal reaction. The IEDDA is the fastest bioorthogonal reaction known so far. Its biocompatibility and ideal kinetics are very appealing for pretargeting applications. The use of a trans-cyclooctene (TCO) and a tetrazine (Tz) in the reaction encouraged researchers to study them deeply. It was found that both reagents are sensitive to acidic or basic conditions. Furthermore, TCO is photosensitive and can be isomerized to its cis-conformation via a radical catalyzed reaction. Unfortunately, the cis-conformer is significantly less reactive toward tetrazine than the trans-conformation. Therefore, extensive research has been carried out to optimize both click reagents and to employ the IEDDA bioorthogonal reaction in biomedical applications. 相似文献
9.
Perpentylated γ-cyclodextrin is a very hydrophobic liquid which exhibits enantioselectivity toward a number of non-polar chiral substrates including the saturated hydrocarbons cis- and trans-pinane, β-chiral olefins, iron(O) tricarbonyl complexes of prochiral olefins and 3,3,8,8-tetramethyl-trans-cyclooctene, a compound with planar chirality. 相似文献
10.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1992,48(8):1083-1090
Gas phase IR spectroscopic measurements of ethyl acetate are reported and the vibrational bands are assigned for the trans—trans and trans—gauche conformers. An extensive ab initio calculation has been carried out for both the conformers to obtain molecular structure, barrier heights, vibrational frequencies, force field, IR intensities and multipole moments. Theoretical calculations are of great help for assignment of the free molecule frequencies, which often show deviation from the condensed phase values. 相似文献
11.
Günter Haufe 《Monatshefte für Chemie / Chemical Monthly》1979,110(1):121-127
The reactions of (E)-cyclooctene withN-bromosuccinimide in the presence of water or methanol are described. Major products of the hydroxybromination aretrans-4-bromocyclooctanol as a product of intermediary transanular hydride migration, and two ring contracted bromohydrines. The methoxybromination has been found to occur similarly.
6. Mitt.:G. Haufe undM. Mühlstädt, Z. Chem., im Druck. 相似文献
12.
Linsheng Feng Eugenijus Urnezius Rudy L. Luck 《Journal of organometallic chemistry》2008,693(8-9):1564-1571
The dioxo molybdenum and tungsten complexes MoO2Cl2(OPPh2CH2OH)2 and WO2Cl2(OPPh2CH2OH)2 have been synthesized and characterized by FT-IR, 1H and 31P NMR. Their structures, as determined by single crystal X-ray diffraction analysis, reveal distorted octahedral geometries with cis terminal oxygen atoms, trans Cl ligands and that the hydroxymethyldiphenylphosphine oxide ligands coordinate through the oxygen atom bonded to the P atom. Both of the compounds are studied as catalysts for the epoxidation of cis-cyclooctene in the presence of hydrogen peroxide as a source of oxygen. Both complexes showed good activity and very high selectivity for the formation of cyclooctene oxide. 相似文献
13.
Ab initio molecular orbital theory with minimal and extended basis sets and a flexible rotor geometric model has been used to investigate the rotational potential surfaces of methyl formate and methyl vinyl ether. For both molecules, the most stable structures (IA and IIA, respectively) are planar cis; additional potential minima are found which correspond to planar trans structures (IB and IIB). The latter lie respectively about 4—8 and 1—2 kcal mol?1 above the corresponding cis rotational isomers. Methyl rotational barriers have been determined for cis and trans structures of each molecule. For trans methyl formate, there is a slight but unexpected preference for an eclipsed arrangement of the methyl group. 相似文献
14.
trans-RhCl(CO)(TPPTS)2 (TPPTS=tris(m-sulfonatophenyl)phosphine) has been intercalated into Zn-Al layered double hydroxides (LDHs) by the method of ion exchange. The structure, composition and thermal stability of the composite material have been characterized by powder X-ray diffraction, Fourier transform infrared and 31P solid-state magic-angle spinning nuclear magnetic resonance spectroscopy, elemental analysis, thermogravimetry, and differential thermal analysis. The geometry of trans-RhCl(CO)(TPPTS)2 was fully optimized using the PM3 semiempirical molecular orbital method, and a schematic model for the intercalated species has been proposed. The thermal stability of trans-RhCl(CO)(TPPTS)2 is significantly enhanced by intercalation, which suggests that such materials may have prospective application as the basis of a supported catalyst system for the hydroformylation of higher olefins. 相似文献
15.
A cis-geometry was proposed for the green complex bis(β-mercaptoethylamine) nickel(II) on the basis of its reactivity, IR spectroscopy and orbital geometry considerations. The crystal and molecular structure of this complex has been determined by X-ray diffraction and shows that the complex has a trans geometry. The crystal structure consists of trans-NiL2 molecules strongly linked through NH-S hydrogen bonds. Electronic and IR spectroscopy, and powder X-ray analysis are in agreement with the same trans geometry for the complexes bis(β-mercaptoethylamine)palladium(II) and bis-(γ-mercaptopropylamine)nickel(II). As a result of the new assignment of the structure of these complexes some concepts, such as its reactivity with nickel(II), are reconsidered. 相似文献
16.
A.S. Gybin W.A. Smti M.Z. Krimer N.S. Zefirov L.A. Novgorodtseva N.K. Sadovaya 《Tetrahedron》1980,36(10):1361-1366
The reactions of the stable S-methylepisutfonium ions derived from cis-cyclooctene with various nucleophiles were found to proceed mainly as the attack at a C atom of episulfonium ring in contrast to the previous data of Helmkamp et al.4 The course of the RSCI AdE-reaction with cyclooctene under the conditions of increased polarity corresponded to the formation of intermediates closely related to episulfonium ions. Transannular 1,5-hydride shift was observed for the reaction of 2,4-dinitrobensenesuilfenyl derivatives with cis-cyclooctene. 相似文献
17.
J Leitich 《Tetrahedron letters》1980,21(32):3025-3028
The relative rates of formation of and [2+2]cycloadducts of benzyne to , - and , -1,5-cyclooctadiene, - and -cyclooctene are discussed and properties of the adducts (e.g., their unusual hydrogenation) are described. 相似文献
18.
The linear dichroism spectra of trans-azobenzene and trans-stilbene aligned in stretched polyethylene films are reported for the u.v.-vis region. On the basis of the results the u.v. transition moment directions with respect to the long molecular axis are determined. Infrared data indicate that trans-azobenzene has a non-planar geometry while trans-stilbene is more planar in the polyethylene matrix. The polarization direction of the nπ* transition in azobenzene is different from that of the first ππ* absorption band, which indicates a vibrational borrowing mechanism corresponding to a nonplanar geometry. 相似文献
19.
《Journal of Coordination Chemistry》2012,65(11):1863-1872
The oxomolybdenum(VI) complex [MoOCl(L)] with a tetradentate glycine bisphenol ligand (H3L) was prepared by reaction of [MoO2Cl2(DMSO)2] with a ligand precursor in hot toluene. The product was isolated in moderate yield as separable cis and trans isomers along with the third minor component, [MoO2(HL)]. The solid-state structure of trans-[MoOCl(L)] was determined by X-ray diffraction. The ligand has tetradentate coordination through three oxygens and one nitrogen, which is located trans to the terminal oxo whereas the sixth coordination site is occupied by a chloride. Both cis and trans isomers of [MoOCl(L)] are active catalysts for epoxidation of cis-cyclooctene and sulfoxidation of tolyl methyl sulfide. The cis isomer gave higher activity in epoxidation and sulfoxidation reactions at room temperature than the trans isomer but they performed identically at 50?°C. 相似文献