The Paramagnetic 2D Chiral—porous Polymer of L—Phenylalanine and Manganese

1 INTRODUCTION Assemblies of chiral and helical structures are common in biology. Molecular materials with chiral porous structures and helical morphology have attracted a great deal of attention in multidiscipli- nary areas such as zeolite-like coordination poly- mers, biomaterials, and chiral chemistry[1～3]. The intensive interest in these materials arises, to a large extent, from their interesting properties and poten- tials in various applications such as electrical con- ductivity, …     

Construction and the Second-order Nonlinear Optics of a New Chiral Coordination Network Based on Two Types of Homo-chiral Helices

A new 2D chiral cadmium coordination network [Cd(TCBA)2]·2EtO H(1) was prepared by the reaction of achiral angular asymmetric bridging ligand 2-((3,5-dimethyl-4H-1,2,4-triazol-4-yl)-carbamoyl)-benzoic acid(TCBA) with cadmium acetate, which was structurally characterized by IR, elemental analysis, thermogravimetric analysis and single-crystal X-ray diffraction. Complex 1 crystallizes in the chiral space group P21 and features a 2D chiral network consisting of two types of homo-chiral helices, which are further extended into a 3D chiral framework along the a-axis via hydrogen bonds. Moreover, powder second-order nonlinear optical(NLO) measurements reveal complex 1 has a modest second-harmonic-generation(SHG) efficiency at room temperature.     

One-dimensional Zigzag Chain Coordination Polymer [Zn(μ-phth)(imi)_2]_∞ Bridged by ο-Phthalato

1 INTRODUCTION The research on coordination polymers is currently of great interest because of their fascinating structure diversity and potential applications as functional materials, which possess potential functions such as molecular recognition, enantiomer separation, chiral synthesis, photoluminescent and selective catalysis[1]. Recently many coordination polymers with special physical and chemical properties have been synthesized and reported[2]. The structures and functions of th…     

Tuning the helical twisting power of nematic liquid crystals induced by chiral 1, 2-propanediol derivatives using varied substituents

In this study,a novel series of chiral 1,2-propanediol derivatives with different electron-donating and electron-withdrawing groups were synthesized and characterized by FT-IR and ~1H NMR.The helical twisting properties of all the chiral dopants were investigated by doping the chiral dopants into a nematic liquid crystal host(SLC-1717).The results indicate that the donor-acceptor electron effect have a prominent influence on helical twisting property of the chiral nematic phase induced by the chiral dopants. Introducing electron-withdrawing groups into the terminal ends of chiral 1,2-propanediol can decrease the absolute values of the helical twisting power.In addition,the helix inversion temperatures of the induced chiral nematic phase are variational with the change of terminal groups.     

Catalytic enantioselective synthesis of β-amino alcohols by nitrene insertion

Chiral β-amino alcohols are important building blocks for the synthesis of drugs, natural products, chiral auxiliaries, chiral ligands and chiral organocatalysts. The catalytic asymmetric β-amination of alcohols offers a direct strategy to access this class of molecules. Herein, we report a general intramolecular C(sp³)–H nitrene insertion method for the synthesis of chiral oxazolidin-2-ones as precursors of chiral β-amino alcohols. Specifically, the ring-closing C(sp³)–H amination of N-benzoyloxycarbamates with 2 mol% of a chiral ruthenium catalyst provides cyclic carbamates in up to 99% yield and with up to 99% ee.The method is applicable to benzylic, allylic, and propargylic C–H bonds and can even be applied to completely non-activated C(sp³)–H bonds, although with somewhat reduced yields and stereoselectivities. The obtained cyclic carbamates can subsequently be hydrolyzed to obtain chiral β-amino alcohols. The method is very practical as the catalyst can be easily synthesized on a gram scale and can be recycled after the reaction for further use. The synthetic value of the new method is demonstrated with the asymmetric synthesis of a chiral oxazolidin-2-one as intermediate for the synthesis of the natural product aurantioclavine and chiral β-amino alcohols that are intermediates for the synthesis of chiral amino acids, indane-derived chiral Box-ligands, and the natural products dihydrohamacanthin A and dragmacidin A.     

Influence of terminal alkyl chain length on helical twisting property of chiral 1,2-propanediol derivatives

In this study,a novel series of chiral 1,2-propanediol derivatives with different terminal alkyl chain length were synthesized and characterized by FT-IR,~1H NMR and DSC.After doped into a nematic liquid crystal host,all the chiral dopants induced chiral nematic liquid crystals exhibiting a helix inversion with temperature variation.The results indicate that terminal alkyl chain length has a prominent influence on helical twisting property of the chiral dopants.With increasing the terminal alkyl chain le...     

Solution Structure and Behavior of Benzophenone-based Achiral Bisphosphine Ligands in Noyori-Type Ru（Ⅱ）-Catalysts

We herein report on solution structural studies of Ru^Ⅱ catalysts （3a, 9） composed of achiral bisphosphine ligands （4, 8） and the enantiopure 1,2-diphenylethylenediamine （DPEN）. Complete chiral induction from enantiopure （R,R）-DPEN to achiral bisphosphine ligand 3a was observed in solution, with the complex adopting a single, stable and non-fluxional （even at 70 ℃） configuration. The coordination of the C=O moiety in 4 to the cationic Run center is considered to be of key importance in providing the higher thermodynamic and kinetic rotation barrier for the flexible bisphosphine ligand in the complex. The obtained enantioselectivity （91% enantiomeric excess） and sense of chiral induction in the hydrogenation of acetophenone were found to be solely dependent on the chirality of the 1,2-diamine. Consistent with the hydrogenation product, the （R,R）-DPEN induces a M-conformation （fight-handed） chirality for flexible phosphine ligand 4 in the complex, resulting in a 2,2-configuration about the Ru^Ⅱ center.     

Construction of three stereocenters via hydrogenative desymmetrization of 2,2,5-trisubstituted cyclohexane-1,3-diones

A Ru-catalyzed hydrogenative desymmetrization of 2,2,5-trisubstituted cyclohexane-1,3-diones was developed for construction of three stereocenters including two coherent and discontiguous chiral centers and a chiral quaternary carbon with excellent enantio-and diastereoselectivities.Stereodivergent synthesis of four stereoisomers could be conducted with high enantioselectivities.The desymmetrization could be achieved at gram scale without loss of reactivity and optical purity,and a formal synthesis of bioactive molecule(-)-isocelorbicol was completed.     

Synthesis and characterization of non-symmetrical liquid crystals containing a cholesteryl ester moiety

In this paper,a series of chiral non-symmetrical liquid crystals(nBA-chol)consisting of a cholesteryl ester moiety as chiral entity and a biphenyl aromatic core with different terminal alkyl chain has been synthesized and investigated for their liquid crystalline properties.Effects of numbers of methylene units in the terminal alkyl chain on the phase transition temperatures and on the temperature-dependent pitch lengths of the chiral liquid crystals have been studied.The long terminal alkyl chain tends ...     

WO3/Salan/30 % H2O2： a Heterogeneous Catalytic System for the Asymmetric Oxidation of Sulfides

Enantiopure sulfoxides constitute a class of the most efficient and versatile chiral controllers and useful synthons in asymmetric synthesis, and they are of great interest in the pharmaceutical industry as biologically significant compounds1. The synthesis of chiral nonracemic sulfoxides with high enantiomeric purity has been a subject of constant interest over the past two decades. The asymmetric oxidation of prochiral sulfides mediated by chiral catalysis has become one of the most efficien…     

手性配位聚合物的构筑及其应用

手性配位聚合物因其结构多样性、可调控性以及潜在的多功能性,已经成为当前化学和材料学的研究热点。在合成中,可以通过选择特定的非手性配体、手性配体、手性溶剂或手性模板剂等来构筑手性配位聚合物。此外,还可以选择特定的金属离子赋予目标手性配位聚合物光、电、磁、催化和非线性光学等性能。本文详细综述了近年来纯手性配位聚合物的合成方法,以及在手性分离、手性催化、非线性光学、铁电和多铁等领域的应用研究进展。最后,对手性配位聚合物的合成方法及应用前景进行了展望。     

Enantioselective Synthesis of a Chiral Coordination Polymer with Circularly Polarized Visible Laser

Circular dichroism is known to be the feature of a chiral agent which has inspired scientist to study the interesting phenomena of circularly polarized light (CPL) modulated molecular chirality. Although several organic molecules or assemblies have been found to be CPL‐responsive, the influence of CPL on the assembly of chiral coordination compounds remains unknown. Herein, a chiral coordination polymer, which is constructed from achiral agents, was used to study the CPL‐induced enantioselective synthesis. By irradiation with either left‐handed or right‐handed CPL during the reaction and crystallization, enantiomeric excesses of the crystalline product were obtained. Left‐handed CPL resulted in crystals with a left‐handed helical structure, and right‐handed CPL led to crystals with a right‐handed helical structure. It is exciting that the absolute asymmetric synthesis of a chiral coordination polymer could be enantioselective when using CPL, and provides a strategy for the control of the chirality of chiral coordination polymers.     

Asymmetric Hydroformylation Using a Rhodium Catalyst Encapsulated in a Chiral Capsule

Supramolecular capsules can be used to change the activity and selectivity of a catalyst through the influence of the second coordination sphere, reminiscent of how enzymes control the selectivity of their processes. In enzymes, this approach is used to also control the enantioselectivity of reactions in which the active catalytic site is often not chiral but the second coordination sphere is. We are interested in the possibility to generate a chiral second coordination sphere around an otherwise achiral transition metal complex for asymmetric catalysis. In this paper we show that the ligand template approach can be used to generate a chiral second coordination sphere around a rhodium complex, which is used in asymmetric hydroformylation.     

氮杂环配体自组装螺旋链状结构配位聚合物的研究进展

螺旋结构配位聚合物在光学装置、生物模拟化学、非对称催化化学、手性识别、生物结构等多学科领域的应用,引起了人们极大的兴趣。本文综述了氮杂环配体自组装螺旋结构配位聚合物的最新进展,按照咪唑、三唑、吡啶、嘧啶及其衍生物配体分类总结了它们构建螺旋配位聚合物的结构,并简述了通过自发手性识别过程得到纯手性螺旋配位聚合物的影响因素,展望了具有螺旋链状配位聚合物的发展前景以及其开发应用潜能。     

Chiral Auxiliaries as Emerging Tools for the Asymmetric Synthesis of Octahedral Metal Complexes

New methods for the stereocontrolled synthesis of octahedral metal complexes are needed in order to fully exploit the stereochemical richness of the octahedron in the fields of catalysis, materials sciences, and life sciences. Whereas a large body of work exists regarding the diastereoselective coordination chemistry with chiral ligands, such efforts are restricted to certain carefully designed chiral ligands which remain in the coordination sphere. The emerging strategy of chiral‐auxiliary‐mediated asymmetric synthesis holds promise to solve the problem of controlling relative and absolute configuration in octahedral metal complexes in a general fashion, thus hopefully in the future providing access to any desired optical active octahedral metal complex without the need for chiral separations. This short review will summarize reported examples of chiral auxiliaries applied to the asymmetric synthesis of octahedral metal complexes.     

Enantioselective supramolecular catalysis induced by remote chiral diols

A new method of creating libraries of chiral diphosphines is presented. Supramolecular coordination compounds based on Ti, Rh, achiral ditopic ligands, and chiral diols were synthesized by in situ mixing and used as catalysts in the asymmetric hydrogenation of (Z)-methyl 2-acetamido-3-phenylacrylate, giving ee's of up to 92%. The ditopic ligands contain a Schiff base that coordinates to the assembly metal Ti and a phosphine as a ligand for Rh. Chirality is introduced by coordination of the chiral diols to Ti. The controlling chiral center and the substrate are separated by as much as 13 ?.     

Nanoscale metal coordination macrocycles fabricated by using "dimeric" dipyrrins

Covalently linked dipyrrin (dipyrromethene) dimers have afforded nanoscale [2+2]-type neutral coordination macrocycles with a diagonal of about 1.6 nm. Two moieties of the achiral dipyrrin-Zn(II) complex yield the chiral coordination macrocycles as minor species, as well as major meso stereoisomers by the covalent linkages. Tetrahedral Zn(II) coordination by using acyclic ligands enables the dipyrrin-metal complex units to readily rotate and pass through the cavity of the nanorings in order to reveal the transitions between the chiral and achiral isomers.     

Chiral recognition of amino acids and dipeptides by a water-soluble zinc porphyrin

A chiral water-soluble zinc porphyrin was optically resolved on a chiral HPLC column, and the binding of chiral amino acids and peptides to each of the enantiomers was examined spectrophotometrically in basic aqueous solution. The binding data apparently indicated that the zinc porphyrin has chiral selectivity for amino acids and dipeptides. This was reasonably explained in terms of the triple cooperation of coordination, Coulomb, and steric interactions of the chiral amino carboxylates with the porphyrin. A compensatory relationship among the thermodynamic parameters for chiral recognition was also shown.     

Separation of enantiomers by gas chromatography

The separation of enantiomers by gas chromatography is performed on chiral stationary phases (CSPs) via hydrogen bonding, coordination and inclusion. Thus, typical chiral selectors are amino acid derivatives, terpene-derived metal coordination compounds and modified cyclodextrins. In Chirasil-type stationary phases the chiral selector is anchored to a polysiloxane backbone improving gas chromatographic performance. The present review article describes the state-of-the-art, scope and limitations, applications and mechanistic considerations at the advent of the millennium incorporating 16 figures and 168 references.     

Lewis acid-mediated radical cyclization: stereocontrol in cascade radical addition-cyclization-trapping reactions

An efficient approach for achieving radical cyclizations by using hydroxamate ester as a coordination tether with Lewis acid was studied. The chiral Lewis acid-mediated cascade radical addition-cyclization-trapping reaction proceeded smoothly with good enantio- and diastereoselectivities, providing various chiral γ-lactams.