共查询到20条相似文献,搜索用时 203 毫秒
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研究了SDP作为双膦配体与金属铑形成的手性催化剂在不对称Pauson-Khand反应中的催化活性和对映选择性, 并考察了影响反应活性和对映选择性的各种因素. 结果表明, SDP配体对铑催化的Pauson-Khand反应是一种有效的手性配体, 它与铑生成的手性催化剂能在1大气压的一氧化碳气氛中, 将一系列1,6-烯炔化合物转化为相应的双环戊烯酮, 反应的对映选择性较高. 在SDP配体中苯环上引入取代基导致反应的对映选择性降低, 但是当取代基为甲氧基时, 催化剂的活性得到明显提高. 溶剂实验表明1,2-二氯乙烷是理想的反应溶剂. 催化剂的阴离子对催化剂活性和对映选择性也有十分重要的影响, 采用六氟锑酸根时, 反应的对映选择性最高. 相似文献
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新型手性配体的设计合成是不对称催化研究的重要内容,其中手性胺膦配体因同时含有"软"的磷原子和"硬"的氮原子而具有丰富的配位化学性能和优秀的不对称诱导能力.本文总结了本研究组最近设计合成的手性环状胺膦配体的制备、表征及其在铁催化酮的不对称还原中的应用.手性1,2-环己二胺与双(2-甲酰基苯基)苯基膦通过[2+2]环缩合反应能够顺利获得手性22元环的亚胺膦配体21,该配体经Na BH4还原后生成大环胺膦配体22.利用手性大环胺膦配体22与Fe3(CO)12原位生成的催化体系,能够高活性、高对映选择性地实现包括杂环芳香酮在内50多种酮的不对称转移氢化和不对称氢化反应,其S/C(底物与催化剂的摩尔比)最高可达5000:1,产物手性芳香醇的光学纯度高达99%ee. 相似文献
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Qian-Yi ZhaoMin Shi 《Tetrahedron》2011,67(20):3724-3732
Axially chiral phosphine-oxazoline ligand L6 was found to be a fairly effective chiral ligand in silver(I)-catalyzed asymmetric Mannich reaction of N-Boc aldimines with trimethylsiloxyfuran to give the corresponding adducts in up to 97% yield, 7:1 dr and 86% ee (major diastereoisomer). 相似文献
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Axially chiral phosphine–oxazoline ligand L7, prepared from (S)-binol, was found to be a fairly effective chiral ligand in the silver(I)-catalyzed asymmetric Mannich reaction of fluorinated aldimines with trimethylsiloxyfuran to give the corresponding adducts in up to 99% yield, over 20:1 dr and 81% ee. 相似文献
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Chikkali SH Bellini R de Bruin B van der Vlugt JI Reek JN 《Journal of the American Chemical Society》2012,134(15):6607-6616
A small family of new chiral hybrid, diphosphorus ligands, consisting of phosphine-phosphoramidites L1 and L2 and phosphine-phosphonites L3a-c, was synthesized for the application in Rh-catalyzed asymmetric hydroformylation of heterocyclic olefins. High-pressure (HP)-NMR and HP-IR spectroscopy under 5-10 bar of syngas has been employed to characterize the corresponding catalyst resting state with each ligand. Indole-based ligands L1 and L2 led to selective ea coordination, while the xanthene derived system L3c gave predominant ee coordination. Application of the small bite-angle ligands L1 and L2 in the highly selective asymmetric hydroformylation (AHF) of the challenging substrate 2,3-dihydrofuran (1) yielded the 2-carbaldehyde (3) as the major regioisomer in up to 68% yield (with ligand L2) along with good ee's of up to 62%. This is the first example in which the asymmetric hydroformylation of 1 is both regio- and enantioselective for isomer 3. Interestingly, use of ligand L3c in the same reaction completely changed the regioselectivity to 3-carbaldehyde (4) with a remarkably high enantioselectivity of 91%. Ligand L3c also performs very well in the Rh-catalyzed asymmetric hydroformylation of other heterocyclic olefins. Highly enantioselective conversion of the notoriously difficult substrate 2,5-dihydrofuran (2) is achieved using the same catalyst, with up to 91% ee, concomitant with complete regioselectivity to the 3-carbaldehyde product (4) under mild reaction conditions. Interestingly, the Rh-catalyst derived from L3c is thus able to produce both enantiomers of 3-carbaldehyde 4, simply by changing the substrate from 1 to 2. Furthermore, 85% ee was obtained in the hydroformylation of N-acetyl-3-pyrroline (5) with exceptionally high regioselectivities for 3-carbaldehyde 8Ac (>99%). Similarly, an ee of 86% for derivative 8Boc was accomplished using the same catalyst system in the AHF of N-(tert-butoxycarbonyl)-3-pyrroline (6). These results represent the highest ee's reported to date in the AHF of dihydrofurans (1, 2) and 3-pyrrolines (5, 6). 相似文献
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采用溴化钯为催化剂前体,与非螯合型双齿膦配体L1(DPPFF)、联吡啶型双齿膦配体L2(P-PHOS)和二茂铁基手性双膦配体L3((S,Rp)-BPPF)制备络合物催化剂,以乙酰丙酮羰基铑为催化剂前体,与手性亚磷酸酯配体L4-L6制备络合物催化剂,将其分别应用于底物环己基甲醛或苯乙醛的不对称酰胺羰化反应中,研究结果表明... 相似文献
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Ya-Shuai Liu Yan Liu Xiao-Wei Ma Ping Liu Jian-Wei Xie Bin Dai 《中国化学快报》2014,25(5):775-778
3-(Diphenylphosphino)propanoic acid(L2) has proved to be an efficient ligand for the copper-catalyzed C–N coupling reactions.N-arylation of imidazoles with aryl iodides catalyzed by CuCl/L2 was smoothly carried out in DMSO at 100 8C with a yield up to 98%.N-arylation of 1H-pyrazole with aryl iodides and bromides catalyzed by Cu(OAc)2/L2 in 1 4-dioxane also gave the corresponding products with yields of40%–98%. 相似文献
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以1.0代聚酰胺-胺(PAMAM)为配体骨架,氯代二苯基膦为原料,通过取代反应合成了1种含有较大空间位阻的新型树枝状PNP配体,再以Cr Cl3(THF)3为络合试剂,通过络合反应合成树枝状PNP铬催化剂.采用傅里叶变换红外光谱(FTIR)、紫外-可见分光光度计(UV-Vis)、核磁共振波谱(NMR)、电喷雾电离质谱(ESI-MS)和元素分析等手段证实合成的新型树枝状PNP配体及其铬催化剂的结构与理论设计的结构一致.以甲基铝氧烷(MAO)为助催化剂,对乙烯齐聚反应进行了研究,考察了溶剂种类、反应温度、反应压力及Al/Cr摩尔比对该催化剂活性和选择性的影响.结果表明,以甲苯为溶剂,MAO为助催化剂,当反应温度为25℃,反应压力为0.9 MPa,Al/Cr摩尔比为500时,该催化剂的活性高达2.15×105g/(mol Cr·h),催化剂对乙烯三聚、四聚反应的选择性共达到36.76%. 相似文献
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E. A. El-Ghany A. A. El-Mohty W. A. Zaghary M. T. El-Kolaly M. Raich A. A. El-Bary 《Journal of Radioanalytical and Nuclear Chemistry》1998,232(1-2):223-228
L,L-ethylenecysteine dimer (L,L-ECD) compound was synthesized with an overall yield 31.2% and a melting point 197–198°C. A
systematic study has been carried out on the labelling of L,L-ECD with technetium-99m by ligand exchange via99mTc-EDTA. The percent labelling yield of L,L-ECD was found ≥95% when 0.75 2.0 mg and 100 μg of L,L-ECD, disodium-EDTA and tin
(II) were used, respectively, at pH 5.5. The produced99mTc-L,L-ECD complex is stable, neutral and lipid soluble. The99mTc-L,L-ECD complex penetrate the blood-brain barrier following intravenous injection in the tail vein of mice with an initial
brain uptake equal to 0.9% at 2 minutes and a slow washout equal to 0.65% after 25 minutes. High uptake in the gastrointestinal
tract (GIT) was observed. It reaches up to 38.9% at 2 minutes and increased as time pass reaching 48.3% at 60 minutes. These
results indicate that this ligand is suitable for brain imaging and has a tendency to be excreted via liver and GIT due to
its lipophilicity. 相似文献
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Rao GK Kumar A Kumar B Singh AK 《Dalton transactions (Cambridge, England : 2003)》2012,41(15):4306-4309
First selenium ligand stabilized Pd(0) nanoparticles (~3-5 nm) catalyze Suzuki-Miyaura C-C coupling in short time and are recyclable (up to 94% yield after 5 reuses). The air stable compound [PdCl(2)(L1)(2)] shows high catalytic efficiency for this coupling as its 3 × 10(-5) mol% is sufficient for activated ArBr. 相似文献