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1.
有机锡在不对称合成中的应用研究进展   总被引:7,自引:0,他引:7  
金属有机化合物是不对称合成中常用的有机试剂。有机锡试剂易于制备,而且碳-锡键又易于断开,因此它们被广泛应用于有机合成中,当然也是不对称合成常用的试剂之一,是制备某些手性天然产物必备的试剂。由于锡的结构特点,它可以形成四配位、五配位甚至六配位的配合物,这些配合物作为路易斯酸可用作不对称合成中的催化剂、助催化剂。从已报道的文献看,大多数反应的产率及对映体选择性都在中等或中等以上水平,某些已达到了优良的水平。本文综述了有机锡作为反应试剂、催化剂、助催化剂在不对称合成中的应用。  相似文献
2.
茉莉醛相转移催化合成法的改良   总被引:4,自引:0,他引:4  
黄文榜  官仕龙 《有机化学》1991,11(5):526-529
茉莉醛又称2-戊基肉桂醛,具有优雅的茉莉花香,是一种深受调香师喜爱的合成香料。目前已广泛应用于各种日用化学品中。  相似文献
3.
Cp2TiCl2/助催化剂体系催化异戊二烯齐聚反应的研究   总被引:1,自引:0,他引:1  
过渡金属催化剂催化异戊二烯齐聚反应, 因其重要的应用背景及学术研究价值而受到人们的关注. 其中研究得最多的是镍催化体系, 采用不同的镍催化体系可以选择性地得到各种线性或环状的二聚物或齐聚物[1,2].  相似文献
4.
助催化剂对N催化剂催化乙烯-苯乙烯共聚反应的影响   总被引:1,自引:0,他引:1  
研究了N催化剂分别与助催化剂AlEt3和Et2 AlOAlEt2 结合 ,在给电子体二苯基二甲氧基硅烷 (DDS)存在下 ,催化乙烯和苯乙烯共聚合反应 ,考察了Al Ti摩尔比对共聚反应的影响 .共聚产物经过丁酮 (MEK)和四氢呋喃 (THF)连续抽提 ,表明共聚产物包括无规聚苯乙烯 ,乙烯 苯乙烯共聚物和乙烯均聚物 .乙烯 苯乙烯共聚物分别用1 3C NMR、DSC和GPC进行表征 ,结果表明 ,助催化剂不仅对N催化剂的聚合活性有影响 ,而且对共聚产物中各级份的重量比例也有显著影响 ;特别是对乙烯 苯乙烯共聚物中苯乙烯的含量、熔点 (Tm)和玻璃化转变温度 (Tg)有明显的影响 .  相似文献
5.
Polymerizations of ethylene have been carried out by using Cp2*Zr(NMe2)2 (Cp*=C5Me5) compound combined with common alkyl aluminums (AlR3) and methylaluminoxane (MAO) as cocatalysts. The AlMe3 cocatalyzed system showed no activity due to the formation of stable but inactive heterodinuclear [Cp2*2Zr(μ-Me)2AlMe2]+ cations; however, the bulkier AlR3 [AlEt3, Al(i-Bu)3 and Al(i-Bu)2H] cocatalyzed systems showed very high activities. Especially, Cp2*Zr(NMe2)2/Al(i-Bu)3 catalyst showed higher catalytic activity and produced higher molecular weight (MW) polymer than Cp2*Zr(NMe2)2/MAO catalyst, demonstrating both MAO and bulky AlR3 are effective cocatalysts for Cp2*Zr(NMe2)2 compound.  相似文献
6.
N,N-Dimethylanilinium salt of molybdenum disulfide (MoS2) was developed as a novel cocatalyst for metallocene catalysts. The cocatalyst is composed of N,N-dimethylanilinium ion as a cationic part and “topotactic” reduction product of MoS2, obtained by acquisition of an electron by neutral host lattice of MoS2 without structural alteration, as an anionic part. In ethylene polymerization, addition of the N,N-dimethylanilinium salt of MoS2 to the bis(indenyl)zirconium dichloride (Ind2ZrCl2)/triethylaluminum (Et3Al) catalyst improved the catalytic activity per mmol of Ind2ZrCl2. The catalytic activity of this system activated by addition of the cocatalyst depended significantly on the amount of the cocatalyst and the N,N-dimethylanilinium ion content in the cocatalyst. Poly(ethylene) and poly(ethylene-co-1-hexene) obtained with the metallocene catalyst activated by addition of the cocatalyst have typical features such as narrow molecular weight distribution and narrow composition distribution like polymers obtained with conventional metallocene catalysts.  相似文献
7.
The effect of adamantane (Ad) has been studied on the activity and selectivity of the H- and Pt/H-forms of zeolite Y and mordenite (MOR) in the hydroisomerization and cracking ofn-heptane at 443 K.Ad was found to induce pronounced increase in the isomerization activity and selectivity of the H-Y zeolite, while the activity of the Pt/H-Y and MOR was only moderately influenced. Findings suggest thatAd acts as a hydride transfer cocatalyst, but, its activity is controlled by the limited accessibility of the active sites within the zeolitic channels.  相似文献
8.
We have studied the palladium-catalyzed alkoxycarbonylation of allyl bromide in supercritical (sc) CO2 and found the reaction rate in sc CO2 was lower than those in some organic solvents1. The possible reason was the lower solubility of sc CO2 for the palladium catalyst. As an effective approach to improve the solubility of varieties of solutes, cosolvent such as ethanol has been widely used in the sc CO2 extraction2,3. Based on the above consideration, we chose several organic reagents…  相似文献
9.
Methylalundnoxane(MAO)isthemostimportantcocatalystformetallocenecatalyzedolefinpolymerization.Intheearlyyearsofthefieldithadbeentheonlycocatalystwhichcanactivatemetallocenecatalyststoveryhighactivity.MAOispreparedbypartialhydrolysisofAl(CHs)s(TMA)undercontrolledconditions1.TMAisanextremelyreactiveanddangerousreagent,andthismakesMAOapreciouschendcalreagent.MAOaccountsforalargepercentageinthecostofthemetallocenecatalystsystem,becauseahighMAO/metalloceneratioisneededforpoIymerization'.I…  相似文献
10.
The heterogeneous bis(cyclopentadienyl)zirconium(IV) dichloride catalyst of the composition MgCl2(THF)/(AlEt2Cl)0.34/(Cp2ZrCl2)0.01 as determined by FTIR, XRD, and AAS analyses was synthesised and, after activation by MAO, applied for ethylene polymerisation. The catalyst turned out to be stable and more active than those magnesium supported catalysts already known from the literature. The polyethylene produced has a relatively high molecular weight (Mw > 200,000 g/mol), a narrow and monomodal molecular weight distribution (MWD = 2.4), a bulk density of about 180 g/dm3, and monomodal particle size distribution. Application of a ternary Al(i-Bu)3/MAO/B(C6F5)3 activator decreased the amount of MAO needed and increased catalyst activity, but did not change the reaction mechanism.  相似文献
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