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991.
手性5-l-(艹孟)氧基丁内酯并[3,4-d]-3-取代基-异(口恶)唑啉类化合物的合成 总被引:2,自引:0,他引:2
研究了手性元5-(R)-(l-(艹孟)氧基)-2(5H)-呋喃酮与取代苯甲醛肟以次氯酸钙作为氧化剂进行的区域选择性原位1,3-偶极环加成反应,同步生成两个新的手性中心,得到了一系列光学纯丁内酯并[3,4-d]-3-取代基-异(口恶)唑啉类化合物;应用波谱学手段及X射线单晶衍射法确证了产物的绝对构型,并对产物的核磁共振氢谱规律性加以总结. 相似文献
992.
Cycloheptatrienes were obtained by the reaction of 2-substituted allylic alcohols with alkynes in the presence of catalytic amounts of palladium complexes and p-toluenesulfonic acid. 相似文献
993.
以99.995% Ce(NO3)3和强碱性阴离子交换树脂为原料,采用离子交换-双氧水氧化法合成制备出纳米CeO2晶体。并就离子交换反应中的Ce3+浓度、树脂加入速度和离子交换温度及H2O2加入速度等条件对CeO2粒径的影响进行了探讨,得出了离子交换-双氧水氧化法制备纳米CeO2晶体的最佳工艺条件。FTIR、TEM分析表明,离子交换法无需对合成的Ce(OH)3溶胶进行洗涤即可去除NO3-、CO32-等阴离子杂质,并用H2O2将该溶胶氧化,经真空干燥可制得粒径分布均匀,平均晶粒尺寸约3 nm,高纯度的CeO2粉体。 相似文献
994.
Metathesis of hex-1-ene in ionic liquids catalyzed by WCl6 was studied. The metathesis is preceded by isomerization of hex-1-ene to hex-2-ene, from which the main reaction product, viz., oct-4-ene, is derived. The WCl6-1-butyl-3-methylimidazolium tetrafluoroborate (BMIM·BF4) system efficiently catalyzes metathesis of linear olefin, the ionic liquid serving as the reaction medium by forming a stable homogeneous catalytic system with WCl6. The yields of the metathesis products increase with increasing reaction temperature. The addition of tin-containing promoters leads to a substantial increase in the reaction rate. In the WCl6-BMIM·BF4-SnBu4 system, the selectivity of the formation of oct-4-ene is significantly enhanced.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2094–2097, October, 2004. 相似文献
995.
Krasnov V. P. Levit G. L. Korolyova M. A. Bukrina I. M. Sadretdinova L. Sh. Andreeva I. N. Charushin V. N. Chupakhin O. N. 《Russian Chemical Bulletin》2004,53(6):1253-1256
The influence of the reaction conditions (solvent, base) on the diastereoselectivity of acylation of (±)-3-methyl-2,3-dihydro-4H-1,4-benzoxazine with (S)-naproxen and N-tosyl-(S)-proline chlorides was studied. The highest diastereoselectivity was observed for the reaction carried out in benzene in the presence of aliphatic tertiary amines. 相似文献
996.
Reactions of organo(trichloromcthyl)silanes RMc2SiCCl3 (R = Me, Ph, Mc3Si) with aluminum chloride have been studied. The interaction of trimetltyl(tricltlorometltyl)silane with AlCl3 carried out in cyclohexane or in benzene leads to Me3SiCHCI2 (in 75 % yield) or ClMe2SiCPh2Me (in 70 % yield), respectively; whereas no conversions are observed inn-hexane and methylene chloride. Treatment of dimetltyl(phenyl)(ricltloromethyl)silane with aluminum chloride in an-C5H12/CH2CI2 mixture gives an aromatic cross-linked insoluble polymer. The reaction of pentamethyl(trichloromcthyl)disilane (R = Mc3Si) with AICl3 in pentane affords the rearrangement product, Me3SiCCl2SiMc2Cl, in 65 % yield. In methylene chloride the further cleavage of the disilane occurs to yield Me2SiCl2 and CH2=CHMe2SiCl.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1511-1515, June, 1996. 相似文献
997.
Duygu Avci Selim H. Kseflu Robert D. Thompson Lon J. Mathias 《Journal of polymer science. Part A, Polymer chemistry》1994,32(15):2937-2945
New ester derivatives of ethyl α-hydroxymethylacrylate were synthesized using acid chlorides (traditional solution reactions), sodium salts of acids (with phase transfer catalysis), and trifluoroacetic anhydride (trifluoroacetate). The interfacial process gave high yields of clean products under very mild conditions. Derivatives obtained include the formate, acetate, hexanoate, stearate, benzoate, trifluoroacetate, and adamantanoate. Bulk polymerizations with 2,2′-azobis (isobutyronitrile) gave high molecular weight polymers with intrinsic viscosities of over 2 dL/g and molecular weights of several million [based on size-exclusion chromatography (SEC) comparison to polystyrene standards]. These high molecular weights were the result of autoacceleration in the bulk as shown by monitoring molecular weight with respect to conversion. Solution polymerization in benzene gave more typical polymer, e.g., the acetate derivative showed an SEC molecular weight of 52,000. Glass transition temperatures for the n-alkyl esters decreased from the formate (77°C) to the hexanoate (15°C); the stearate showed a side-chain melting point of 40°C but no Tg. Glass transitions were observed for the trifluoroacetate, benzoate, and adamantanoate polymers at 69, 130, and 214°C, respectively. Solution 13C-NMR showed evidence of tacticity information for the formate and acetate derivatives with appaent preference for syndiotactic polymer formation similar to that of methyl methacrylate. FTIR and solid-state 13C-NMR analysis gave spectra with functional group peaks and chemical shift values expected based on composition. The stearate monomer and polymer gave solid-state 13C chemical shifts of 34 and 33 ppm, respectively, for the central CH2 units consistent with monoclinic and orthorhombic crystal packing. © 1994 John Wiley & Sons, Inc. 相似文献
998.
999.
Alkylation of 3-nitro-1,2,4-triazole and 5-methyl-3-nitro-1,2,4-triazole with dialkyl sulfates or alkyl halides in the presence
of alkali proceeds with a low selectivity for the alkylating agent with the formation of two regioisomers at the N(1) and N(2) atoms of the heterocycle. Depending on the reaction conditions the proportion of the N(2) isomer was 14.6-33.8%.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1020–1025, July, 2005. 相似文献
1000.
Migration behavior and enantioseparation of racemic hydrobenzoin and structurally related compounds, including benzoin and benzoin methyl ether, in CZE with a dual CD system consisting of heptakis-(2,3-dihydroxy-6-O-sulfo)-beta-CD (SI-S-beta-CD) and beta-CD as chiral selectors in the presence and absence of borate complexation at pH 9.0 were investigated. The results indicate that enantioseparation of hydrobenzoin is mainly governed by CD complexation of hydrobenzoin-borate complexes with SI-S-beta-CD when SI-S-beta-CD concentration is relatively high. Whereas CD complexation of hydrobenzoin-borate complexes with beta-CD plays a significant role in enantioseparation when SI-S-beta-CD concentration is comparatively low. The (S,S)-enantiomer of the hydrobenzoin-borate complex was found to interact more strongly than the corresponding (R,R)-enantiomer with both SI-S-beta-CD and beta-CD. These two types of CD show the same chiral recognition pattern, but they exhibit opposite effects on the mobility of the enantiomers of hydrobenzoin-borate complexes. Enantiomer migration reversal of hydrobenzoin occurred in the presence of borate complexation when varying the concentration of beta-CD, while keeping SI-S-beta-CD at a relatively low concentration. Binding constants of the enantiomers of benzoin-related compounds to beta-CD and those of hydrobenzoin-borate complexes to SI-beta-CD were evaluated; the mobility contributions of all complex species to the effective mobility of the enantiomers of hydrobenzoin as a function of beta-CD concentration in a borate buffer were analyzed. In addition, comparative studies on the enantioseparation of benzoin-related compounds with SI-S-beta-CD and with randomly sulfate-substituted beta-CD were made. 相似文献