X-ray photoelectron spectroscopic analysis of effect of EB on electronic state of Ti species in TiCl4/MgCl2/EB Ziegler-Natta catalysts

Donor free TiCl4/MgCl2 Ziegler-Natta catalysts could not be successfully used to produce polypropylene ini- tially because of their low stereospecificity for propyl- ene polymerization. The addition of Lewis bases as internal donors and external donors to…     

Recent advances in catalytic asymmetric hydrogenation： Renaissance of the monodentate phosphorus ligands

The history for the development of chiral phosphorus ligands in catalytic asymmetric hydrogenation is briefly highlighted. This review focuses on the recent advances in the synthesis of the monodentate phosphorus ligands and their applications in catalytic asymmetric hydrogenation. The examples highlighted in this article clearly demonstrated the importance and advantages of monodentate phosphorus ligands, which had been ignored for 30 a and experienced a renaissance at the very beginning of this millennium, particularly in the area of asymmetric hydrogenation.     

Absolute Asymmetric Synthesis Using A Cocrystal Approach

1 Results Absolute asymmetric synthesis by means of solid-state reaction of chiral crystals self-assembled from achiral molecules is an attractive and promising methodology for asymmetric synthesis because it is not necessary to employ any external chiral source like a chiral catalyst.In order to design reliably absolute asymmetric syntheses in the solid state,it is inevitable to prepare and predict the formation of chiral crystals from achiral compounds.We have prepared a number of chiral cocrystals co...     

La/Ca改性NiO/MgO耐高温氨分解催化剂制备

采用MgO为载体,以La及Ca掺杂对其改性,以Ni为活性组分,制备了La/Ca改性NiO/MgO氨分解催化剂,试验测试了催化剂物化性能,结果表明La/Ca改性NiO/MgO耐高温氨分解催化剂的耐热性能达1450℃、强度达1480N/颗。     

二茂铁衍生物的手性HPLC分离

以γ-缩水甘油醚氧丙基三甲氧基硅烷为连接臂,合成了β-环糊精键合硅胶固定相(CDs).研究了二茂铁衍生物的手性HPLC分离,结果表明此固定相对手性二茂铁衍生物有很好的分离能力.优化了色谱分离条件,讨论了可能的分离机理,并考察温度对二茂铁衍生物手性分离的影响,实验所选取的温度都低于对映体转折温度Tiso,在该实验温度范围内,固定相构型未发生明显变化;保留机制及对映选择作用不变;Δ(ΔH0)和Δ(ΔS0)均为负值,说明该化合物的拆分为焓驱动过程.     

铜锰基SBA-15催化剂的制备及其甲苯燃烧消除的催化性能

以介孔分子筛SBA-15为载体,采用浸渍法分别制备了Cu、Mn和CuMn（物质的量比为1∶1）的质量分数为5%～17%的Cu/SBA-15、Mn/SBA-15和CuMn/SBA-15催化剂,以及Ce质量分数为2.5%～7%、CuMn（物质的量比为1∶1）质量分数为12%的Ce/CuMn/SBA-15催化剂,在常压固定床反应器上评价了这些催化剂对甲苯催化燃烧的反应性能,用X-射线衍射、透射电镜、程度升温还原等分析手段对催化剂的结构进行了研究。活性评价结果表明,Cu质量分数大于12%时,Cu/SBA-15催化剂具有好的活性;Mn质量分数大于8%时,Mn/SBA-15催化剂具有好的活性;CuMn质量分数大于8%时,CuMn/SBA-15催化剂具有好的活性。并且相同Cu、Mn质量分数的双组分催化剂比单组分催化剂的活性要好,在Ce/CuMn/SBA-15催化剂中,Ce质量分数为2.5%～3.5%时,能提高催化剂的活性。结构研究表明,所有催化剂的SBA-15介孔结构仍然保持,并且Cu、Mn等活性组分都已分散在SBA-15分子筛的孔道中。在Ce/CuMn/SBA-15催化剂中,Ce质量分数小于5%时能促进CuMn的分散,并且提高了催化剂的氧化还原能力。     

不对称Heck反应合成手性哌啶衍生物

手性哌啶骨架广泛存在于药物和活性天然产物分子中。本研究发展了一种新型不对称Heck反应,用于合成手性哌啶衍生物。通过对反应条件进行筛选,得到了最优反应条件：催化剂为[Pd(allyl)Cl]₂（5 mol %）,配体为L5（10 mol %),NaOMe（3.0 equiv）作碱,在110℃的混合溶剂（PhMe/MeOH = 5/1）中回流反应20 h。该不对称Heck反应显示出良好的底物普适性,可用于构建多种含有季碳中心的手性哌啶衍生物。     

Application of modified amino acid as a chiral building block in asymmetric synthesis

Phenylglycine 1 as a representative of natural resourceful α-amino acid was modified by reduction and protection of functional group to afford the amino alcohol as a chiral building block 3. A new chiral compound, the chiral building block/spiro-cyclopropane derivative containing four stereogenic centers, compound 7, has been obtained in 52% yield with de⩾98% via the tandem double Michael addition/internal nucleophilic substitution under mild condition of 5-l-menthyloxy-3-bromo-2-(5H)-furanone 4 with the nucleophilic reagent, the amino alcohol 3. The new chiral compound 7 is identified on the basis of its analytical data and spectroscopic data, such as UV, IR,¹H NMR,¹³C NMR, MS and elementary analysis. The absolute configuration of the interesting spiro-cyclopropanes 7 was established by X-ray crystallography. This result can provide new route and method for the introduction of chiral building block and the important synthetic strategy in synthesis of some complex molecules containing spiro-cyclopropane skeleton with multiple chiral centers and the study of their biological activity.     

N-正丁基吡啶-L-脯氨酸盐手性离子液体的合成及表征

以L-脯氨酸为手性源,合成了吡啶类手性离子液体,并进行了结构表征。以吡啶和溴代正丁烷为原料采用微波法合成中间体溴化N-正丁基吡啶,再与氢氧化钾、L-脯氨酸制备N-正丁基吡啶-L-脯氨酸盐手性离子液体,反应过程简单,产物具有较好的收率。测定了化合物N-正丁基吡啶-L-脯氨酸盐的比旋光度,考察了其光学活性和电导率。     

光学活性胺的不对称合成

采用前手性的酮1a-d为原料,R-或S-α-苯乙胺为手性试剂,经3步反应合成光学活性的胺类化合物4a-d.全部合成过程不用昂贵试剂,不用加压,立体选择性在中等以上,总产率39%～50%.亚胺化反应的时间长短对产物的E/Z选择性有明显影响,降低还原温度有助于提高立体选择性.