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61.
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
62.
Ken-ichi Ogu 《Journal of fluorine chemistry》2003,124(1):69-80
Treatment of allylic alcohols with hexafluoropropene-diethylamine adduct (PPDA) afforded N,N-diethyl-2-fluoro-2-trifluoromethyl-4-alkenamides which were formed by the Claisen rearrangement of intermediary 2-alkenyl-1-diethylamino-2,3,3,3-tetrafluoro-1-propenyl ethers. Although (E)-allylic alcohols gave two diastereomeric products in about 1:1 ratio, (Z)-allylic alcohols gave the corresponding product as a single diastereomer. 相似文献
63.
To make clear the reason of unsuitability of poly(vinyl alcohol) (PVA) protective colloid for the emulsion polymerization
of conjugated monomers, a model experiment of emulsion polymerization of methyl methacrylate (MMA) was carried out with ammonium
persulfate (APS) or azobis(isobutyronitrile) (AIBN) initiators, where a small amount of MMA (1/100th of the concentration
compared with ordinary emulsion polymerization) was employed. This corresponds to the initial stage of the emulsion polymerization.
Grafting of MMA onto PVA took place remarkably irrespective of the kind of the initiators. Formation of homo-poly(MMA) was
observed to a small extent. The formation of new emulsion particles smaller than 100 nm continued to increase to almost the
end of the polymerization. PVA molecules in the grafted polymer are supposed to act as stabilizers of newly formed particles.
From kinetic treatment using the experimental data, the important issues were derived as follows. Firstly, the sulfate anion
radical from APS is much more reactive than the isobutyronitrile radical from AIBN in terms of hydrogen abstraction from PVA.
Secondly, high grafting ability of the latter initiator system, notwithstanding the much lower reactivity in the hydrogen
abstraction compared with the APS system, is attributed to the relative reactivity of the primary radicals, i.e., hydrogen
abstraction reaction from PVA to initiation reaction with MMA. The much slower rate of addition of the isobutyronitrile radical
to the monomer compared with that of hydrogen abstraction from PVA facilitates the grafting, although the rate constant of
hydrogen abstraction is far smaller than that with the sulfate anion radical by 10−4 times.
Received: 26 April 2001 Accepted: 6 September 2001 相似文献
64.
锌和锡参与下末端环氧化物的选择性烯丙基化反应 总被引:1,自引:0,他引:1
烯丙基溴和金属辛或锡成功地将末端环氧化合物1一锅法合成高烯丙基醇2和双高烯丙基醇3. 还研究了环氧化合物取代基的影响, 并提出了此烯丙基化的反应途径 . 相似文献
65.
Jörg Fridgen Georg Eickerling Ana M. Santos 《Journal of organometallic chemistry》2004,689(17):2752-2761
Novel chiral 2′-pyridinyl alcohols derived from isopropylidene-protected carbohydrates are reported. They show different characteristics at the hydroxy group, but are all suitable ligands for chiral molybdenum(VI) complexes of the type MoO2L2 (L = chiral 2′-pyridinyl alcoholate). MoO2(acac)2 served as starting material in the complex syntheses. The structure of one ligand and one dioxo complex were exemplary established by X-ray crystallography. For catalytic runs in the enantioselective epoxidation catalysis trans-methylstyrene was used as model substrate, tert-butylhydroperoxide and cumolhydroperoxide, resp., as the oxidant. 相似文献
66.
Ahmed Abd El-Fattah Mohamad Nageeb Hassan Ahmad Rashad Mona Marei Sherif Kandil 《International Journal of Polymer Analysis and Characterization》2020,25(5):362-373
Abstract An injectable composite hydrogel composed of polyvinyl alcohol (PVA) and bioactive glass (BG) particles were synthesized by a physical crosslinking approach. The morphology, mechanical properties, and viscoelasticity of the PVA/BG composite hydrogel were characterized. Scanning electronic microscopy (SEM) showed uniform and homogeneous distribution of BG particles throughout the composite hydrogel. The incorporation of 2.5?wt% of BG particles in the composite hydrogel formulations, enhanced the static compressive strength and static elastic modulus by 325% and 150%, respectively. The storage molds (G′) was greater than the loss modules (G′′) at all the frequency range studied, which revealed a self-standing elastic composite hydrogel with a smooth injectability. The PVA/BG composite hydrogel was also implanted subcutaneously in the dorsal region of adult male rats. After 4?weeks of implantation, no inflammatory cells were seen within and around the implant, which indicated that the composite hydrogel was biocompatible. The properties of the synthesized injectable PVA/BG composite hydrogel demonstrate its capability toward bone regeneration. 相似文献
67.
新型糠醛加氢制糠醇催化剂研究 总被引:8,自引:0,他引:8
新型糠醛加氢制糠醇催化剂研究林培滋,黄世煜,周焕文,赵彤彤,刘崇早,罗洪原,梁东白(中国科学院大连化学物理研究所,大连116023)关键词铜催化剂,糠醛,加氢,糠醇糠醇是重要的化工原料,糖醇树脂是耐酸、碱腐蚀的材料,在工业发达的国家中,铸造工业广泛采... 相似文献
68.
贵金属对钴基催化剂上肉桂醛选择加氢反应的影响 总被引:5,自引:0,他引:5
研究了贵金属改性的Co/γ-Al2O3催化剂上的肉桂醛选择加氢反应.结果表明,通过Pt,Pd和Ru贵金属改性,提高了催化剂的活性,但只有Pt改性的催化剂具有较高的选择性.w(Pt)<0.5%时,催化剂的活性随着Pt含量的增加呈直线升高,当w(Pt)=0.5%时,催化剂活性可提高近5倍,但催化剂的选择性变化很小.XRD结果表明,催化剂经还原后,γ-Al2O3上的钴主要为α-Co0.TPR结果表明,Pt的加入提高了Co3O4的还原性能,且Pt含量越高,Co3O4的还原温度越低.XPS结果表明,Pt改性的催化剂样品,其Co3O4大部分被还原为Co0.由于Pt与Co具有协同效应,故Pt改性的Co/γ-Al2O3催化剂既具有较高的活性,又具有很高的选择性. 相似文献
69.
70.
A direct catalytic asymmetric Mannich-type reaction of isomerizable aliphatic imines is described. A Et2Zn/(S,S)-linked-BINOL complex was suitable for chemoselective enolate formation from a hydroxyketone in the presence of isomerizable aliphatic N-diphenylphosphinoyl imines. The reaction proceeds smoothly and β-alkyl-β-amino-α-hydroxyketones were obtained in good yield and high enantioselectivity (up to 99% ee), albeit in modest to low diastereoselectivity. 相似文献