共查询到20条相似文献,搜索用时 15 毫秒
1.
S. L. Malhotra 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(4):533-552
Abstract The nature of the initiating and propagating species involved in the anionic polymerization of α-methylstyrene has been explored. The earlier hypothesis that multimodal GPC molecular weight distributions in polymers arise solely out of different reaction steps or different ion-pair mechanisms being involved has been modified for poly-α-methylstyrene. Multimodal GPC molecular weight distributions in poly-α-methylstyrene initiated with potassium at 25°C and polymerized at 25°C or higher in THF, p-dioxane, or cyclohexane as solvents have been ascribed to the presence of two different types of tetramers which grow simultaneously but at different rates, each responding to its own well-defined thermodynamic equilibrium and yielding dormant and living polymers. Reaction schemes describing the initiation (at 25°C) and propagation reactions (between -25 and 60°C) in the polymerization (in solution of THF as well as in bulk) of α-methylstyrene initiated with potassium-naphthalene, butyl-lithium, and butyllithium-tetramethylethylenediamine (TMEDA) have been presented. The role of coordinating agents naphthalene and TMEDA in changing irreversible propagations into reversible ones has been emphasized. 相似文献
2.
V. M. Lyubchanskaya L. S. Sarkisova L. M. Alekseeva V. G. Granik 《Chemistry of Heterocyclic Compounds》1992,28(3):299-303
The process of condensation of p-benzoquinone with the secondary cyclic enamines 2-(2-nitromethylene)pyrrolidine, -piperidine, and -hexahydroazepine is very much dependent on the size of the saturated ring in these compounds. With increasing ring size, the content of derivatives of 5-hydroxybenzofuran decreases, and the quantity of derivatives of 5-hydroxyindole increases; with the seven-membered enamine, a substituted 6-hydroxyindole is also formed. For enamines of the pyrrolidine and piperidine series, 1,4-bis-2-(2-nitromethylene)pyrrolidono- or piperidinohydroquinones are also recovered.For Communication 71, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 357–362, March, 1992. 相似文献
3.
New bimolecular sulfur-containing -phenylethylamines and N-benzyltetrahydroisoquinolines have been synthesized from formyl derivatives of diaryl sulfides. The possibility of using metals as catalysts for obtaining diaryl sulfides in the reaction of ortho-substituted benzaldehydes with SCl2 has been shown for the first time.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 731–735, September–October, 1995. Original article submitted November 11, 1994. 相似文献
4.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1976,32(8):1471-1476
The solvent shift method of BELLAMY is re-examined, particularly as a tool for the identification of vibrations that include and are coupled to carbonyl, all of which show solvent sensitivity. For α,β-unsaturated ketones, it is shown that s-cis and s-trans conformers are readily distinguished by plots of νCC vs. νCO. The nature of this coupling is discussed and it is concluded that, in so far as coupling occurs, νCO and νCC take on the character of out-of-phase and in-phase modes respectively. In either conformer, the in-phase (νCC) mode gains in relative intensity as the frequencies converge. While s-cis conformers couple more, conjugation is unaffected by this; the true index of conjugation is neither νCO nor νCC but mean frequency νm. The whole of the solvent effect appears to be relayed by carbonyl: even a highly polar carbon double bond is insensitive to solvent unless so coupled. 相似文献
5.
R. Nurdinov É. É. Liepin'sh I. Ya. Kalvin'sh 《Chemistry of Heterocyclic Compounds》1993,29(11):1352-1357
When N-methoxycarbonyl and N-benzoxycarbonyl derivatives of methyl esters of aziridine-2-carboxylic acid, L-proline, L-thioproline, and pipecolic acid interact with NaBH4 in tert-butanol/methanol, the products of reduction of the C-methoxycarbonyl group of the original compounds are accompanied by bicyclic urethanes and oxazolidines. Reduction of N-maleates and N-fumarates of heterocyclic -iminocarboxylic acids leads to the formation of -hydroxymethyl-N-[4-(2-oxo-2,5-dihydrofuryl)] derivatives of pyrrolidine, piperidine, 1,3-thiazolidine, and 1,4-thiazan. In the latter case, 1-aza-2-hydroxymethyl-4-oxo-5-oxa-9-thiabicyclo [5.4.0]undecene-2 is also obtained. The N-maleates and fumarates of aziridine-2-carboxylic acid are reduced anomalously by sodium borohydride, forming 2-hydroxymethyl-2-(-hydroxyethyl)-3-oxa-1-azabicyclo[3.1.0]hexanes.For Communication 3 see [2].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1567–1573, November, 1993. 相似文献
6.
Recently, anions of “protected” cyanohydrins have been introduced as useful acyl carbanions equivalents in organic synthesis2. Continuing with our interest in the use of these reagents for natural product syntheses3, we wish to report a short total synthesis of the sesquiterpene α-bisabololone 1 4,5, whose salient feature is a novel application of “protected” cyanohydrins to the synthesis of β-hydroxy ketones. 相似文献
7.
H. Tanaka 《Journal of Thermal Analysis and Calorimetry》2000,60(3):715-720
Bibliography
List of Selected Papers of Prof. Dr. Jaroslav Šesták 相似文献8.
《Tetrahedron letters》1986,27(15):1723-1726
α-Metallo benzylselenides and α-metallo selenoacetals derived from aromatic aldehydes have been conveniently prepared by metallation of the corresponding carbon acids. KDA in THF proved among the various basic systems tested, the most efficient.α-Metallo benzylselenides and α-metallo selenoacetals derived from aromatic aldehydes have been conveniently prepared by metallation with KDA of the corresponding carbon acids. These reactions have been used for the synthesis of arylalkanes, including those bearing a trialkylated benzylic carbon, from aromatic aldehydes. 相似文献
9.
B. T. Ibragimov Z. G. Tiljakov K. M. Beketov S. A. Talipov 《Journal of inclusion phenomena and macrocyclic chemistry》1997,27(2):99-104
The formation of host-guest complexes of gossypol at different temperatures has been investigated for the same pressure and concentration. Gossypol forms three different clathrates with dichloromethane within the temperature interval of 22-36 °C. Single crystals of these three modifications (phases) were obtained and their crystallographic parameters measured. The structure of the -phase has been determined previously and the -phase is isostructural to the inclusion complex of gossypol with benzene, while the structure of the -phase has been solved during the present research. Crystals of C30H30O8·CH2Cl2 are triclinic, space group P1, a = 8.604(1), b = 11.858(2), c = 14.405(2) (Å), = 84.60(1), = 89.14(1), = 89.73(1)°, V = 1463(1) Å3, Z = 2, R = 0.089 for 2419 observed reflections.Under ambient conditions gossypol forms unstable tubulates of the -phase; the -phase is a stable cage-type clathrate (cryptate) and the host-guest complex of the -phase is a clathrate of intermediate tubulato-cryptate type. 相似文献
10.
11.
《Tetrahedron letters》1986,27(22):2513-2516
(β-Phenylseleno carbamates have been synthesized by reaction of olefins with phenylselenenyl chloride and carbamates in presence of silver tetrafluoroborate. This reaction constitutes a good method for the conversion of olefins to β-functionalized protected amines. 相似文献
12.
I. Zh. Zhalolov V. U. Khuzhaev K. K. Turgunov B. Tashkhodzhaev S. F. Aripova 《Chemistry of Natural Compounds》2003,39(3):289-291
An indole alkaloid of the N-methyl-tetrahydro--carboline series was isolated for the first time from Arundo donax, Poaceae. Its structure was solved by X-ray structure analysis. 相似文献
13.
14.
15.
《Tetrahedron letters》1988,29(51):6773-6774
Tert-butyl isocyanide reacts with acetals, in presence of diethylaluminium chloride, to afford α-iminonitriles. 相似文献
16.
Three new flavonol glycosides were isolated from the leaves of Helicia nilagirica Beed.The structures were elucidated as kaempferol-3-O-β-D-xylopyranosyl-(1→6)-β-D-glyco-pyranosyl-(1→2)-α-L-rhamnopyranoside,quercetin-3-O-β-D-xylopyranosyl-(1→6)-β-D-glycopy-ranosyl-(1→2)-[-β-D-xylopyranosyl-(1→4)]-α-L-rhamnopyranoside,and quercetin-3-O-β-D-xylopyranosyl-(1→6)-β-D-glycopyranosyl-(1→2)-α-L-rhamnopyranoside,nmaed as Hcilcianeoside A、B and C ,respectively. 相似文献
17.
The reactions of 3-chloropropylphosphonates, 3-chloropropylthiophosphonates, or 3-chloropropylphosphinates with 2-aryloxyethylamines or N-phenylpiperazine afford the corresponding 3-(2-aryloxyethylamino)propylphosphonates and -phosphinates or 3-(4-phenylpiperazin-1-yl)propylphosphonates and -phosphinates. The compounds obtained exhibit -adrenolytic and hypotensive activities, the latter being found to depend on the substituents at the P atom. 相似文献
18.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1980,36(7):621-625
The i.r. spectra of the Li, Na and K salts of β-ketoaldehydes, RCOCH2CHO (R = Me, Et, i-Pr and t-Bu) in DMSO, methanol and water were investigated. Assignments of bands to stretching modes of particular configurations of the enolate system were given. Influence of the cation radius on the Z,Z ⇌ E,E/Z,E equilibrium and of the substituent R on the E,E ⇌ Z,E equilibrium was observed. Shifts of the enolate bands in protic solvents were observed and hydrogen-bond formation accounted for this phenomenon. 相似文献
19.
20.
Tong WU De Yun KONG Hui Ting LI* Shanghai Institute of Pharmaceutical Industry Shanghai 《中国化学快报》2002,13(11)
Helicia nilagirica Beed. belongs to the plant of Proteaceae family. The seeds of the plant is for treatment of insomnia and neurasthenia in Jingpo nationality in Yunnan Province1. Helicid and helicidol were isolated from the seeds of the plant2,3, and the helicid was recorded in the Yunnan Pharmacopoea at the 1987 edition. The chemical constituents of the leaves of this plant has not been reported yet in the literature. This paper is concerning the study of the chemical component of the… 相似文献