桥联茂钛配合物催化丙烯聚合反应选择性的理论研究

采用密度泛函方法对3种不同类型的硅桥联茂钛配合物[Me_2SiN(Me_4Cp)TiCl_2(A),Me_2SiCpFluTiCl_2(B)及Me_2SiInd_2TiCl_2(C)]催化丙烯聚合反应的选择性进行了理论研究.计算结果表明,硅桥联茂金属配体的空间结构是其催化烯烃聚合反应的区域选择性和立体选择性的主要原因.聚合过程中,α-烯烃配位有1,2插入(一级插入)和2,1插入(二级插入)2种方式,3种硅桥联茂金属催化剂均表现为烯烃的一级插入,这种区域选择性与催化剂硅桥联配体的刚性结构密切相关.对烯烃聚合反应链增长机理进行了理论计算,结果表明,具有Cs对称性的Me_2SiN(Me_4Cp)TiCl_2和Me_2SiCpFluTiCl_2催化丙烯聚合分别得到无规立构和间规立构的聚烯烃产物,而具有C_2对称性的Me_2SiInd_2TiCl_2催化丙烯聚合得到等规立构的聚烯烃产物,与实验结果一致.     

膦亚胺半茂钛催化体系合成无规聚丙烯弹性体的研究

采用2种膦亚胺半茂化合物[(t-Bu)_3P=N]CpTiCl_2(PT1)和[(t-Bu)_3P=N]CpTiMe_2(PT2)为主催化剂,分别以甲基铝氧烷(MAO)或[Ph_3C][B(C_6F_5)_4]为助催化剂用于丙烯聚合研究.详细考察了不同n(Al)/n(Ti)、反应温度、反应压力、反应时间等因素对丙烯聚合活性、分子量与分子量分布及其分子结构的影响.还与典型的(rac-[En(IndH_4)_2]ZrCl_2)(1),CpTiCl_3(2)及Cp_2TiCl_2(3)催化剂的催化效果进行了比较.凝胶渗透色谱(GPC)、核磁共振氢谱与碳谱(1H/13C-NMR)、示差扫描量热分析(DSC)和红外(FTIR)分析结果表明:这2种催化剂催化丙烯聚合的活性可高达3.25×10~6g聚合物/molTi×h,重均分子量高达4.4×10~5,分子量分布2.0.降低温度及升高反应压力和延长反应时间都能使聚丙烯分子量增加.观察到聚合初期产物分子量随聚合时间线性增大.在-100~200oC范围内没有观察到熔融峰出现,但在-3.7~-2.6oC区间可以观察到有玻璃化转变温度出现.序列结构分析表明,所生成的聚丙烯为无规结构,但二元组r(62.28%)高于m(37.72%),意味着聚合过程中有间规聚合倾向.[mr/(2mm+mr)]+[mr/(2rr+mr)]=1.04的计算结果进一步说明,由此类催化剂体系催化丙烯聚合生成的产物立体结构序列分布服从伯努利统计模型,聚合主要以1,2-插入方式为主,同时含有少量2,1-插入.     

双核苯氧亚胺类催化剂的制备及烯烃聚合

合成了5个不同结构的苯氧亚胺配体L1～L5,用Et_3N,Me_3SiCl或HNa处理后与TiCl_4·2THF或CpZrCl_3·DME进行配位反应得到不同取代基结构的化合物C1～C6,经过~1H NMR,~(13)C NMR,IR和元素分析等表征,确认了化学结构.以甲基铝氧烷(MAO)为助催化剂,化合物C1～C6为催化剂催化乙烯聚合,考察了聚合温度、乙烯压力、铝钛或铝锆比对催化剂活性及聚合物分子量的影响.聚合实验结果表明,刚性桥基结构提高了双核化合物(LMCl_3)_2的稳定性,催化剂的活性基本都能达到10~5～10~~6g/(mol M·h),其中C5的催化活性最高,达到1. 23×10~6g/(mol Zr·h); C4在Al/Ti摩尔比为50∶1时也具有较好的催化活性[5. 89×10~5g/(mol Ti·h)],聚合物分子量1. 11×10~6.该类催化剂还可以有效催化乙烯与1-辛烯共聚,1-辛烯插入率达到10. 65%(摩尔分数).     

双组分茂金属催化剂催化乙烯聚合的研究

选择能形成支链的不对称桥联茂金属化合物Me2 C[(Cp) (Ind) ]ZrCl2 和非桥联的不同结构的茂金属化合物二氯二 (烯基取代环戊二烯 )锆如 ( Cp) 2 ZrCl2 ,(Cp) 2 ZrCl2 和 (Cp) 2 ZrCl2 ,以MAO为助催化剂 ,分别组成三组双组分茂金属催化剂的催化体系 ,催化乙烯聚合 .结果表明 ,两类催化剂组成的双组分茂金属催化体系催化乙烯聚合能得到支化的宽分子量分布的聚乙烯 ;聚合温度和改变两种茂金属催化剂的摩尔比对催化活性和分子量有很大影响 .因此可以利用改变双组分茂金属催化剂的摩尔比例和聚合温度来调控聚合物的分子量和分子量分布 .改变两种茂金属催化剂的摩尔比和聚合温度也能使聚合物的结晶度发生改变     

HOMO- AND COPOLYMERIZATION OF ETHYLENE CATALYZED BY ANSA-METALLOCENES WITH DOUBLY HETERO-BRIDGES

Three ansa-metallocenes(Me_2C)(Me_2Si)Cp_2TiCl_2(1),[(CH_2)_5C](Me_2Si)Cp_2TiCl_2 (2)and (Me_2C)(Me_2Si)Cp_2ZrCl_2 (3)with larger dihedral angles and longer distance from metal to the center of Cp planes were synthesized and used as catalysts for ethylene polymerization in the presence of methylaluminoxane (MAO).In the case of ethylene polymerization,compared the feature structures of unbridged metallocenes, singly bridged metallocenes and doubly bridged metallocenes 1,2,3,there exhibit the relationship ...     

MgBu_2/AlEt_2Cl为助催剂的钛催化剂上丙烯聚合动力学——Ⅰ.烷基金属浓度的影响

烯烃聚合催化剂种类繁多,改变金属离子或配位体能得到性能不同的烯烃聚合催化剂.可供选择的助催化剂主要有烷基铝,烷基氯化铝,铝氧烷和Cp_2MtMe化合物等(Mt=Ti,V,Zr,Hf).有实用价值的助催化剂只有烷基铝或烷基氯化铝.对丙烯聚合非载体钛系催化剂而言,AlEt_2Cl是较好的助催化剂,而对载体型MgCl_2/TiCl_4钛系催化剂,较好的助催化剂则是AlEt_3.如果将MgBu_2与AlEt_2Cl的混合物用     

芳基亚胺桥联双核茂钛络合物催化乙烯聚合

 采用芳基亚胺桥联双核茂钛络合物催化乙烯聚合反应,考察了茂环上不同取代基、聚合温度、聚合时间和助催化剂用量对络合物催化活性和所得聚合物分子量的影响. 结果表明,该类络合物催化乙烯聚合的活性很高,所得聚合物具有较高的分子量和较宽的分子量分布. 络合物催化活性最高可达3.420×105 g/(mol·h),所得聚合物分子量最高可达659345 g/mol,分子量分布最宽为Mw/Mn=5.88. 茂环上的取代基增大,络合物的催化活性提高,而且催化活性随着助催化剂甲基铝氧烷(MAO)用量的增大而增大. 聚合时间为1.0 h和聚合温度为60 ℃时,络合物的催化活性最高.     

三乙基铝调控的Ziegler-Natta/茂金属复合催化剂制备聚丙烯催化合金

基于具有"反应器颗粒技术(RGT)"特征的Ziegler-Natta/茂金属复合催化剂(MgCl2/TiCl4/racEt(Ind)2ZrCl2),以三乙基铝(AlEt3,TEA)和烷基铝氧烷(MAO)分别作为Ti和Zr 2种催化剂组分的助催化剂,利用TEA对茂金属Zr中心在丙烯均聚反应中的阻聚作用,以及乙烯对"失活"中心的活性复原,实现了复合催化剂中茂金属Zr中心在聚丙烯催化合金(丙烯均聚+乙烯/丙烯共聚)过程中的"可逆失活".基于这种方法,以MgCl2/TiCl4/rac-Et(Ind)2ZrCl2为催化剂,TEA/MAO为助催化剂,通过一步法(催化剂和助催化剂一次加入)制备了新型聚丙烯催化合金,聚丙烯基体(PP)选择性地由Ti金属中心生成,而乙丙共聚物(EPR)则有相当大的比例由茂金属Zr中心生成.与完全由Ziegler-Natta催化剂所产生的聚丙烯催化合金相比,新型合金中的EPR共聚序列结构更加无规,同时EPR保持在PP基体中均匀分散.     

MgCl_2/AlEt_n(OEt)_(3-n)负载单茂钛催化剂催化乙烯聚合研究

以MgCl2/AlEtn(OEt)3-n为载体,分别负载五甲基茂基三氯化钛(Cp*TiCl3)和五甲基茂基三苄氧基钛(Cp*Ti(OBz)3),得到两种负载催化剂,在较廉价的AlEt2Cl为助催化剂常压下可以高效地催化乙烯聚合.报道了载体的制备、聚合条件(不同的烷基铝助催化剂、聚合温度、铝钛摩尔比)对催化剂的聚合行为以及聚合物结构的影响.研究结果表明,两种负载催化体系对乙烯聚合具有较高的催化活性,可达105g PE/(molTi·h)数量级,所得聚乙烯的黏均分子量在105以上.经过13C-NMR和DSC分析,两种负载催化剂得到的均为线型聚乙烯.与均相催化剂相比,负载后的单茂钛催化体系的聚合反应动力学表现高效而平稳.这表明载体的微孔结构使活性中心得到了有效的分散,有效地提高了催化剂的活性,同时载体的受限空间有效抑制了聚乙烯增长链的β-H消除反应.     

茂钛对乙烯基单体的催化聚合——Ⅷ.二氯二茂钛催化乙烯基单体聚合机理的证明

本文以 UV 和~1HNMR 跟踪方法研究了二氯二茂钛(Cp_2TiCl_2)在二甲亚砜中的光化学反应,用自旋捕获技术来捕获 Cp_2TiCl_2催化丙烯腈单体聚合体系中所生成的自由基.UV 和~1HNMR 跟踪结果表明,Cp_2TiCl_2逐渐分解并生成环戊二烯.ESR 测定表明,用自旋捕获剂 PBN 和 BNO 都捕获到了环戊二烯自由基.进一步证明了 Cp_2TiCl_2催化乙烯基单体聚合反应是一种自由基机理.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.