A novel chiral porous metal-organic framework: asymmetric ring opening reaction of epoxide with amine in the chiral open space

A novel chiral metal-organic framework, [Cu(2)(5,5'-BDA)(2)] was synthesized by treating chiral 2,2'-dihydroxy-1,1'-binaphthalene-5,5'-dicarboxylic acid (5,5'-H(2)BDA) with a Cu(II) ion, in which the asymmetric ring opening reaction of an epoxide with amine proceeds efficiently under solvent-free conditions.     

One dense and two open chiral metal-organic frameworks: crystal structures and physical properties

Three 3D robust homochiral helical coordination polymers, [Cu(2,2',3,3'-H2odpa)(bpy)] (1), {[Ni4(2,2',3,3'-odpa)2(bpy)4(H2O)4].(H2O)16} (2), and {[Co4(2,2',3,3'-odpa)2(bpy)4(H2O)4].(H2O)14} (3), have been hydrothermally synthesized from a flexible ligand of 2,2',3,3'-odpda (2,2',3,3'-oxydiphthalic dianhydride). Compound 1 crystallized in space group P3(1)21 and has a rare chiral dense qzd 7.(5)9 topology that incorporates single helical substructures with the same accessibility, whereas compounds 2 and 3 crystallized in the space group C2 and possessed isostructural 3D chiral open frameworks based on the homochiral 2D sheets and 4,4'-bpy pillars. TGA and PXRD analyses show that the porous framework of 2 is stable after the removal of solvent water molecules. In contrast, 3 changed its structure to an amorphous one because of the simultaneous loss of solvent and coordination water molecules. 1 is nearly paramagnetic, whereas weak ferromagnetic interactions between M(II) (M = Ni, Co) ions have been found in 2 and 3.     

Enhancement of catalytic activity for hydrogenation of nitroaromatic by anionic metal-organic framework

Nitroaromatic hydrogenation catalysis without precious metals remains a longstanding challenge. The rate of electron transfer is the crucial factor affecting hydrogenation catalysis. Herein, an ionic Cd-based metal-organic framework(I-Cd-MOF) exhibiting a unique structure with one-dimensional(1D) opening nanochannels and good electron transfer ability was synthesized for catalyzing hydrogenation of 4-nitrophenol(4-NP). The catalytic activity of the unique I-Cd-MOF without noble metals is detecte...     

Synthesis,characterization and catalytic performance of Mo based metal-organic frameworks in the epoxidation of propylene by cumene hydroperoxide

Two types of Mo containing metal-organic frameworks, denoted as Mo@COMOC-4 and PMA@MIL-101 (Cr), were synthesized respectively by a post-synthetic modification and a ship-in-bottle approach. The catalytic performance of both compounds in the epoxidation of propylene using cumene hydroperoxide (CHP) as oxidant was compared with MoO₃@SiO₂. A higher conversion (46.2%) and efficiency (87.4%) of CHP was observed for Mo@COMOC-4, whereas the heteropoly acids supported MIL-101 resulted in the decomposition of CHP due to its strong acidic character. Regenerability tests demonstrated that Mo@COMOC-4 could be reused for multiple runs without significant loss in both activity and stability. © 2017 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.     

Two metal-organic frameworks based on a double azolium derivative: post-modification and catalytic activity

A new bifunctional N-heterocyclic carbene (NHC) precursor was used to construct two metal-organic frameworks, which can anchor palladium(II) sites by post-modification, presenting remarkable framework dependent catalytic activities.     

Cyclohexane selective oxidation over metal-organic frameworks of MIL-101 family: superior catalytic activity and selectivity

Mesoporous metal-organic frameworks Cr- and Fe-MIL-101 are highly efficient, true heterogeneous and recyclable catalysts for solvent-free selective oxidation of cyclohexane with molecular oxygen and/or tert-butyl hydroperoxide under mild conditions.     

Asymmetric alkene epoxidation catalysed by a novel family of chiral metalloporphyrins: effect of structure on catalyst activity,stability and enantioselectivity

A selection of alkenes has been epoxidised with iodosylbenzene, catalysed by three related iron(III) tetraarylporphyrins: 1*, 2* and 3* with four 2,6-di(1-phenylbutoxy)phenyl groups, with one pentafluorophenyl and three 2,6-di(1-phenylbutoxy)phenyl groups and with two pentafluorophenyl and two 2,6-di(1-phenylbutoxy)phenyl groups, respectively. 1* is very sterically hindered and prone to self-oxidation which makes it a relatively poor epoxidation catalyst. Introducing the smaller pentafluorophenyl groups, in place of 2,6-di(1-phenylbutoxy)phenyl, increases catalyst reactivity, stability and selectivity. This change allows easier access of the substrates to the active oxidant and also, by decreasing the electron density on the porphyrin ligand, increases the reactivity of the oxoiron intermediate and its stability towards self-oxidation. A family of five homochiral catalysts, 1, 2 and 3, [the analogues of 1*, 2* and 3*, prepared from (R,R)-2,6-di(1-phenylbutoxy)benzaldehyde] and catalyst 4 with three pentafluorophenyl and one (R,R)-2,6-di(1-phenylbutoxy)phenyl group and 5 the manganese(III) analogue of 3 have been used to epoxidise three prochiral alkenes. All the reactions give low enantioselectivities. Using styrene as the substrate, (S)-styrene epoxide is the major enantiomer obtained with all the catalysts except 1 which leads to the (R)-styrene epoxide being preferred. In contrast cis-hept-2-ene and 2-methylbut-2-ene give the same major epoxide enantiomer with all the catalysts. The dependence of the ee values on catalyst and substrate structure, temperature and solvent is examined and discussed.     

Electronically tuned chiral ruthenium porphyrins: extremely stable and selective catalysts for asymmetric epoxidation and cyclopropanation

We report the use of three enantiomerically pure and electronically tuned ruthenium carbonyl porphyrin catalysts for the asymmetric cyclopropanation and epoxidation of a variety of olefinic substrates. The D(4)-symmetric ligands carry a methoxy, a methyl or a trifluoromethyl group at the 10-position of each of the 9-[anti-(1,2,3,4,5,6,7,8-octahydro-1,4:5,8-dimethanoanthracene)]-substituents at the meso-positions of the porphyrin. Introduction of a CF(3)-substituent in this remote position resulted in greatly improved catalyst stability, and turnover numbers of up to 7500 were achieved for cyclopropanation, and up to 14,200 for epoxidation, with ee values typically >90 % and approximately equal to 80 %, respectively. In one example, the axial CO ligand at the ruthenium was exchanged for PF(3), resulting in the first chiral ruthenium porphyrin with a PF(3) ligand reported to date. In cyclopropanations with ethyl diazoacetate, the latter catalyst performed exceedingly well, and gave a 95 % ee in the case of 1,1-diphenylethylene as substrate.     

Kinetic separation of propene and propane in metal-organic frameworks: controlling diffusion rates in plate-shaped crystals via tuning of pore apertures and crystallite aspect ratios

A series of isostructural, noncatenated, zinc-pillared-paddlewheel metal-organic framework materials has been synthesized from 1,2,4,5-tetrakis(carboxyphenyl)benzene and trans-1,2-dipyridylethene struts. Substantial kinetic selectivity in the adsorption of propene over propane can be observed, depending on the pore apertures and the rectangular-plate morphology of the crystals.     

The first montmorillonite‐supported surface single‐structure titanium complex: synthesis,characterization and catalytic activity in alkene epoxidation

A well‐defined single‐site titanium‐modified montmorillonite (MMT) with only one geometric construction ((?SiO)₃–Ti–NMe₂) was obtained in moderate conditions. Reaction of tetrakis(dimethylamido)titanium with hydroxylated MMT was conducted by surface organometallic chemistry technique, and the surface structure was characterized by in situ Fourier transform infrared spectroscopy, ¹³C cross polarization magic angle spinning nuclear magnetic resonance, X‐ray photoelectron spectroscopy, extended X‐ray absorption fine structure, and elemental analysis. The catalytic activity in alkene epoxidation was evaluated, and the results revealed that the steric hindrance of the substances is responsible for the catalytic activity of the MMT‐supported titanium complex but to the characteristic restricted layer‐like structure of the MMT. Copyright © 2014 John Wiley & Sons, Ltd.     

Chiral imidates as a new class of nitrogen-based chiral ligands: synthesis and catalytic activity in asymmetric aziridinations and diethylzinc additions

Chiral imidates were efficiently synthesized in one step and with high yields (seven examples). These chiral imidates were used as ligands in the Cu(I)-catalyzed asymmetric aziridination of methyl cinnamate and in the asymmetric diethylzinc additions to benzaldehyde as a proof of principle. The imidate catalyst system showed high catalytic activities and induced encouraging selectivities. An X-ray structure analysis of an imidate-Cu(I) complex is included, showing a distorted tetrahedral arrangement with two bidentate ligand molecules surrounding the metal.     

Energy-gaining formation and catalytic behavior of active structures in a SiO(2)-supported unsaturated Ru complex catalyst for alkene epoxidation by DFT calculations

The formation and catalytic behavior of active structures in a SiO(2)-supported unsaturated Ru complex catalyst for alkene epoxidation were studied by means of hybrid density functional theory (DFT) calculations. An energy-gaining route for the catalyst activation was found to allow the formation of active unsaturated Ru complexes and the remarkable alkene epoxidation via an exothermic reaction path between isobutyraldehyde and oxygen. In the proposed Bartlett mechanism, Ru promotes the formation of peracid intermediate and facilitates the intermolecular hydrogen transfer in the peracid intermediate, while alkene molecules do not directly coordinate to the Ru site. It was found that stilbene epoxidation is easier to achieve than ethene epoxidation thanks to the electron donating phenyl groups.     

Molybdenum(VI)-complexes with chiral N,O-ligands derived from carbohydrates: synthesis, structure and catalytic properties in asymmetric olefin epoxidation

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.     

Catalytic epoxidation of olefins using MoO3 and TBHP: Effect of the addition of chiral 2-substituted pyridines on the catalytic rate and asymmetric induction

Attempts were made at epoxidising enantioselectively some simple olefins using MoO₃ (0.17 mol%), TBHP and five different chiral non-racemic 2-substituted pyridine ligands. A maximum conversion of 88% using 4-methylstyrene, and a maximum selectivity of ≥98% using 1-methylcyclohexene and 1-phenylcyclohexene were obtained. All ligands screened showed the ability to accelerate the reaction. However, it was ligand 4, that was the quickest to do so and showed the greatest acceleration. The observation of a reaction rate acceleration in the presence of such ligands appeared to indicate the formation of a Mo(VI)oxoperoxy-ligand complex. In no case was asymmetric induction observed.     

Synthesis of new tridentate chiral aminoalcohols by a multicomponent reaction and their evaluation as ligands for catalytic asymmetric Strecker reaction

A one-step, multicomponent Mannich-type reaction between phenols, paraformaldehyde, and β-aminoalcohols in the presence of LiCl afforded N-2-hydroxybenzyloxazolidines with high ortho-selectivity. Hydrolytic or reductive ring opening of the oxazolidines provided a series of N-salicyl-β-aminoalcohols in 84-92% overall yield. The synthesized compounds were evaluated as ligands for a titanium-catalyzed catalytic asymmetric Strecker reaction. The reaction employing 10 mol % of catalyst provided the Strecker products in excellent yields and up to 98% ee.     

Polystyrenes with chiral phosphoramide substituents as Lewis base catalysts for asymmetric addition of allyltrichlorosilane: enhancement of catalytic performance by polymer effect

In the asymmetric addition of allyltrichlorosilane to benzaldehyde, polystyrenes with chiral phosphoramide substituents as Lewis base catalysts showed up to 2.4 times better catalytic activity and 1.4 times higher enantioselectivity than the corresponding low-molecular-weight analogues.     

刚性双(三氮唑)和羧酸混合配体构建的两种金属有机骨架材料及其在CO2环加成反应中的催化性质

通过酸碱混合配体策略合成了 2 例含刚性双三氮唑配体的金属有机骨架(MOF)材料：{[Zn₂(L)(TP)₂(H₂O)·H₂O]}_n (1)和[Zn(L)(HTMA)]_n (2),其中L=4,4''-(3,3''-dimethyl-(1,1''-biphenyl)-4,4''-diyl)bis(4H-1,2,4-triazole),H₂TP=对苯二甲酸,H₃TMA=1,3,5-均苯三甲酸。用单晶 X 射线衍射表征其结构。结构分析表明,MOF 1显示出 3,6-双节点的二维结构,其拓扑符号为(4²·6)2(4⁸·6⁶·8),MOF 2呈现为经典的 sql二维拓扑结构。在温和条件下,2对 CO₂与环氧化物的环加成反应具有优异的催化活性,且重复使用至少3次后仍然保持其催化性能。     

刚性双(三氮唑)和羧酸混合配体构建的两种金属有机骨架材料及其在CO2环加成反应中的催化性质

通过酸碱混合配体策略合成了 2 例含刚性双三氮唑配体的金属有机骨架(MOF)材料：{[Zn₂(L)(TP)₂(H₂O)·H₂O]}_n (1)和[Zn(L)(HTMA)]_n (2),其中L=4,4''-(3,3''-dimethyl-(1,1''-biphenyl)-4,4''-diyl)bis(4H-1,2,4-triazole),H₂TP=对苯二甲酸,H₃TMA=1,3,5-均苯三甲酸。用单晶 X 射线衍射表征其结构。结构分析表明,MOF 1显示出 3,6-双节点的二维结构,其拓扑符号为(4²·6)₂(4⁸·6⁶·8),MOF 2呈现为经典的 sql二维拓扑结构。在温和条件下,2对 CO₂与环氧化物的环加成反应具有优异的催化活性,且重复使用至少3次后仍然保持其催化性能。     

Amination of N-aryl prolinol via ring expansion and contraction: application to the chiral ligand for the catalytic asymmetric reaction

Chiral diaminophosphines 4 were prepared from (S)-prolinol-derived aminophosphine oxide 5 by bromination with ring expansion followed by amination with ring contraction and reduction, using trichlorosilane. In the presence of 4 as a ligand, palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate (11) with a dialkyl malonate-BSA-LiOAc system was successfully carried out with good enantioselectivities (up to 98% ee).