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1.
Sergiy V. Rosokha Jian Jiang Lu Sergey M. Dibrov Jay K. Kochi 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(8):o464-o466
The title compound, C6H2N6O10·2C2H4Cl2, forms layered stacks of pentanitroaniline molecules, which possess twofold symmetry. The voids between these stacks are occupied by dichloroethane molecules, which reside near a 2/m symmetry element and display pseudo‐inversion symmetry. The C atoms in one of the two solvent molecules are threefold disordered. In the pentanitroaniline molecule, considerable distortion of the benzenoid ring, coupled with the short C—N(H2) bond and out‐of‐plane NO2 twistings, point to significant intramolecular `push–pull' charge transfer at the amino‐ and nitro‐substituted (ortho and para) positions, as theoretically quantified by natural bond orbital analysis of the π‐electron density. 相似文献
2.
A general method is described for asymmetric synthesis of both syn- and anti-1,3-amino alcohols. The first application of metalloenamines derived from N-sulfinyl imines is reported for the highly diastereoselective addition to aldehydes. The reduction of the product beta-hydroxy N-sulfinyl imines 2 with catecholborane and LiBHEt(3) provides syn- and anti-1,3-amino alcohols with very high diastereomeric ratios. This method was found to be effective for a variety of substrates incorporating either aromatic or various aliphatic substituents. The convergent and efficient asymmetric syntheses of the two natural products, (-)-8-epihalosaline and (-)-halosaline, were also accomplished. 相似文献
3.
Bridged diarenes form very strong [1:1] complexes with nitrosonium/nitric oxide in which the NO moiety is optimally sandwiched in the cleft between a pair of cofacial aromatic rings which act as a molecular "Venus flytrap". The spectral features of these associates are generally similar to those for [1:1] and [2:1] nitrosonium complexes with mononuclear alkyl-substituted benzenes, and they are appropriately described within the LCAO molecular-orbital methodology and the Mulliken (charge-transfer) formulation of donor/acceptor electronic transitions. The thermodynamics study indicates that the efficient binding is determined by (i) the close matching of the donor/acceptor redox potentials and (ii) the ability of bridged diarenes for multicentered interactions with a single NO moiety. The best fit of the electronic and structural parameters is provided by a calixarene host that allows the interacting centers to be arranged in a manner similar to those extant in [2:1] nitrosonium complexes with analogous (nonbridged) aromatic donors; this results in its very strong noncovalent binding with nitrosonium/nitric oxide with the formation constant of K(B) approximately 10(8) M(-)(1) and free-energy change of -DeltaG degrees = 45 kJ mol(-)(1). Such strong, selective, and reversible bindings of nitrosonium/nitric oxide by (cofacial) aromatic centers thus provide the basis for the development of efficient NO sensors/absorbents and also suggest their potential relevance to biochemical systems. 相似文献
4.
Strong (orange/red) colourations resulting immediately upon the exposure of nitrogen dioxide and its equilibrium dimer (dinitrogen tetroxide) to various aromatic hydrocarbons (ArH) are shown to arise from the nitrosonium EDA or electron donor-acceptor complexes [ArH, NO+NO 3 ? ]. The latter exhibit diagnostic charge-transfer absorptions and characteristic N-O stretching bands in the UV-vis and IR spectra, respectively, that relate directly to ArH/NO+ interactions extant in the EDA complexes previously derived from the authentic nitrosonium salt, NO+PF 6 - . Time-resolved picosecond spectroscopy establishes the charge-transfer excited state of [ArH, NO+NO 3 ? ] to be essentially identical to that from [ArH, NO+BF 4 ? ]. Furthermore, the same temporal decay of the spectral transients (ArH+?) from both systems indicates minimal ion-pairing effects of the counterions (NO 3 ? and BF 4 ? ) on the kinetics of back electron transfer. 相似文献
5.
Keisuke Kato Chie Matsuba Hiroyuki Takayama Tomoyuki Mochida Tat'yana A. Peganova Oleg V. Gusev 《Tetrahedron》2006,62(42):9988-9999
The oxidative cyclization-carbonylation of meso-2-alkyl-2-propargylcyclohexane-1,3-diols mediated by Pd(II) with chiral bisoxazoline (box ligand) afforded bicyclic-β-alkoxyacrylates. Based on a ligand screening, 2,2′-isopropylidenebis[(4S,5R)-4,5-di(2-naphthyl)-2-oxazoline] ligand has been developed. The products with a chiral quaternary carbon were obtained in 71-100% yields with 85-95% ee. 相似文献
6.
Peroxotungstate immobilized on ionic liquid-modified silica as a heterogeneous epoxidation catalyst with hydrogen peroxide 总被引:6,自引:0,他引:6
Yamaguchi K Yoshida C Uchida S Mizuno N 《Journal of the American Chemical Society》2005,127(2):530-531
Peroxotungstate immobilized on ionic liquid-modified SiO2 is capable of heterogeneously epoxidizing a wide range of olefins with the maintenance of the catalytic activity of homogeneous analogue. The epoxidation was immediately stopped by the removal of the catalyst, and no tungsten species could be found in the filtrate after the removal of the catalyst. These results can rule out any contribution to the observed catalysis from the tungsten species that leached into the reaction solution, and the observed catalysis is truly heterogeneous in nature. Furthermore, the catalyst was reusable without the loss of the catalytic performance. 相似文献
7.
Kamoda S Nomura C Kinoshita M Nishiura S Ishikawa R Kakehi K Kawasaki N Hayakawa T 《Journal of chromatography. A》2004,1050(2):211-216
Carbohydrate chains in glycoprotein pharmaceuticals have important roles for the expression of their biological activities. Therefore, development of an assessment method for the carbohydrate chains is an important parameter for quality control of glycoprotein pharmaceuticals such as newly developed therapeutic antibodies. In this report, we applied capillary electrophoresis with laser-induced fluorescence detection to the analysis of carbohydrate chains after releasing with glycoamidase followed by derivatization with 3-aminobenzoic acid. We found that four major oligosaccharides present in antibody pharmaceuticals were successfully separated with good resolution. The present method showed good precision in both migration times and relative peak areas, and gave comparable accuracy with that using a derivatization method with 8-aminopyrene-1,3,6-trisulfonate. 相似文献
8.
Iida T Satoh H Maeda K Yamamoto Y Asakawa K Sawada N Wada T Kadowaki C Itoh T Mase T Weissman SA Tschaen D Krska S Volante RP 《The Journal of organic chemistry》2005,70(23):9222-9229
[Reaction: see text]. The synthesis of neuropeptide Y antagonist 1, currently under clinical investigation for the treatment of obesity, is described. The convergent synthesis from trans-spirolactone carboxylic acid intermediate 2a and aminopyrazole 3 is predicated on a stereoselective route to the former. The coupling reaction of ethyl 4-oxocyclohexanecarboxylate (10a) with lithiated isonicotinamide 11 was investigated in detail, but even optimized conditions only provided a 45:55 ratio of trans:cis isomers (12a:12b). While selective crystallization schemes were developed to isolate the thermodynamically less stable trans isomer 2a, improved stereocontrol was subsequentially achieved by the application of ketene chemistry. The ketene formation and quench was investigated under a variety of conditions aimed at maximizing the trans:cis ratio. Reacting a mixture of carboxylic acids 2a and 2b with POCl3 in THF, followed by concomitant addition of tert-butyl alcohol in the presence of TMEDA at 35 degrees C provided a 4:1 ratio of trans:cis tert-butyl esters (18a:18b) via in situ ketene formation. Ester hydrolysis, followed by selective crystallization of undesired 2b as the HCl salt, led to isolation of 2a in 47% overall yield. Aminopyrazole intermediate 3 was synthesized via the condensation reaction of 2-fluorophenylhydrazine hydrochloride (4a) with acrylonitrile derivative 5 in 65-70% yield. Coupling of advanced intermediates 2a and 3b via activation with thionyl chloride gave a 92% yield of 1. 相似文献
9.
Shinya Hamasaki Chie Sawauchi Masami Kamigaito Mitsuo Sawamoto 《Journal of polymer science. Part A, Polymer chemistry》2002,40(4):617-623
A fast living radical polymerization of methyl methacrylate (MMA) proceeded with the (MMA)2? Cl/Ru(Ind)Cl(PPh3)2 initiating system in the presence of n‐Bu2NH as an additive [where (MMA)2? Cl is dimethyl 2‐chloro‐2,4,4‐trimethyl glutarate]. The polymerization reached 94% conversion in 5 h to give polymers with controlled number‐average molecular weights (Mn's) in direct proportion to the monomer conversion and narrow molecular weight distributions [MWDs; weight‐average molecular weight/number‐average molecular weight (Mw/Mn) ≤ 1.2]. A poly(methyl methacrylate) with a high molecular weight (Mn ~ 105) and narrow MWD (Mw/Mn ≤ 1.2) was obtained with the system within 10 h. A similarly fast but slightly slower living radical polymerization was possible with n‐Bu3N, whereas n‐BuNH2 resulted in a very fast (93% conversion in 2.5 h) and uncontrolled polymerization. These added amines increased the catalytic activity through some interaction such as coordination to the ruthenium center. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 617–623, 2002; DOI 10.1002/pola.10148 相似文献
10.
Jay K. Kochi 《Angewandte Chemie (International ed. in English)》1988,27(10):1227-1266
The broad varieties of organic and organometallic reactions merge into a common unifying mechanism by considering all nucleophiles and electrophiles as electron donors (D) and electron acceptors (A), respectively. Comparison of outer-sphere and inner-sphere electron transfers with the aid of Marcus theory provides the thermochemical basis for the generalized free energy relationship for electron transfer (FERET) in Equation (37) and its corollaries in Equations (43) and (44) that have wide predictive applicability to electrophilic aromatic substitutions, olefin additions, organometallic cleavages, etc. The FERET is based on the conversion of the weak nucleophile–electrophile interactions extant in the ubiquitous electron donor—acceptor (EDA) precursor complex [D, A] to the radical ion pair [D⊕, A?], for which the free energy change can be evaluated from the charge-transfer absorption spectra according to Mulliken theory. FERET analysis thus indicates that the charge-transfer ion pairs [D⊕, A?] are energetically equivalent to the transition states for nucleophile/electrophile transformations. The behavior of such ion pairs can be directly observed immediately following the irradiation of the charge-transfer bands of various EDA complexes with a 25-ps laser pulse. Such studies confirm the radical ion pair [Arene⊕, NO2] as a viable intermediate in electrophilic aromatic nitration, as presented in the electron-transfer mechanism between arenes and the nitryl cation (NO) electrophile. 相似文献