Chromatographic Separation of the Enantiomers of a Series of C2-Asymmetric Bi-Naphthyl Compounds by Molecularly Imprinted Polymers

The aim of this study was to observe the chiral separation of a series of C₂-asymmetric bi-naphthyl compounds on molecularly imprinted polymers (MIPs) using 1,1′-bi-2-naphthol (BINOL) as template. MIP prepared using 4-vinylpyridine as the functional monomer showed better chiral recognition for the template than the MIPs prepared using acrylamide, 2-(diethylamino)ethylmethacrylate and 2-vinylpyridine, respectively. ¹H-NMR was used for comparison of the interactions between template and functional monomers. For chromatographic analysis the effects of mobile phase and temperature on the chiral separation were investigated. When 4-vinylpyridine was employed as the functional monomer, chiral separation of 1,1′-bi-2-naphthol and its analogues were studied. The MIP also demonstrated an ability to discriminate between enantiomers of structurally related compounds that had not been imprinted. The thermodynamic parameters of interactions between substrates and MIP in acetonitrile based mobile phase were investigated by the Van’t Hoff equation. In this study, the specific hydrogen-bonding interactions seemed to be the key factor to achieve chiral separation.     

以混旋邻氯扁桃酸为模板的分子印迹聚合物的制备及拆分性能研究

以混旋邻氯扁桃酸为模板分子和合成的(S)-(1-萘乙基)-丙烯酰胺为手性功能 单体制备分子印迹聚合物作为色谱固定相，对混旋邻氯扁桃酸有较好的拆分能力， 分离因子α达到1.36。但对模板分子的类似物混旋扁桃酸和对氯扁桃酸没有拆分能 力。用Hyperchem软件模拟了(S)-邻氯扁桃酸与(S)-(1-萘乙基)-丙烯酰胺形成的复 合物的结构模型，其在聚合物母体中留下的具有立体构型和作用力双重识别的S-S 型空穴，对(S)-邻氯扁桃酸有较强的保留作用，从而达到对混旋物拆分的目的。     

右旋邻氯扁桃酸分子印迹聚合物的制备及结合特性研究

以右旋邻氯扁桃酸为模板分子合成了具有高选择性的分子印迹聚合物作为手性分离材料 .紫外光谱研究说明在聚合开始之前模板分子与功能单体形成了配合物 ,并用Hyperchem软件模拟其分子结构 ,结合能分别为 -1 643 7× 1 0 4 J·mol- 1 和 -4 2 799× 1 0 4 J·mol- 1 .分子印迹聚合物对模板分子的结合量高于其它类似物 ,手性分离因子α达 1 76.Scatchard分析表明分子印迹聚合物在识别右旋邻氯扁桃酸分子过程中存在两类结合位点 ,与配合物模拟结构数目一致     

Chiral Resolution of Racemic 4-Phenyl(benzyl)-2-Oxazolidone by Use of Molecularly Imprinted Polymers

Polymers imprinted with (S)-4-phenyl-2-oxazolidone and (S)-4-benzyl-2-oxazolidone have been prepared by non-covalent imprinting. A combinational procedure was used to optimize the functional monomer and crosslinker. A copolymer of methacrylic acid and divinylbenzene resulted in the best chiral recognition. The ratio of template to functional monomer and solvent in the pre-polymerization mixture were also optimized. The imprinted polymers were used as stationary phases in high-performance liquid chromatography. The MIPs were more selective when prepared using a less polar solvent, except for toluene. Effective separations of the enantiomers of racemic 4-phenyl-2-oxazolidone and 4-benzyl-2-oxazolidone were achieved by use of acetonitrile as mobile phase; no cross-selectivity was observed. Interactions between functional monomers and template were investigated by ¹H NMR spectroscopy. The results suggest that hydrogen-bonding between the functional monomer and the template and π–π stacking interaction between the cross-linker and the template may contribute to chiral recognition.     

Selective Synthesis of [2＋2] Macrocyclic Schiff Bases from Chiral 1,4-Diamines

[2＋2] macrocyclic Schiff bases of three kinds have been synthesized from chiral 1,4-diamines by use of different methods. Macrocyclic Schiff bases 1a-1c have been selectively obtained based on a non-templated dilution method from chiral 1,4-diamines a-c and dialdehyde DA1, whereas macrocycles 2a-2c have been selectively produced from reaction of diamines a-c and dialdehyde DA2 in the presence of boric acid as templates. Macrocyclic Schiff bases 3a-3c have been afforded in high selectivity from diamines a-c and dialdehyde DA3 by means of sodium-template. All the titled compounds have been confirmed by ^1H NMR and ESI-MS analyses.     

以凝聚子聚集体为模板制备TiO2纳米材料及其性质研究

合成了一种可用作凝聚子(Gelator)并带正电荷的胆固醇酯类化合物.研究其在溶剂中的聚集行为,并以其聚集体为模板,通过Sol-gel方法制备了一维TiO2纳米材料.改变凝聚子和TiO2前驱体的用量比,用扫描电镜观察到生成的TiO2纳米材料具有不同的尺寸和形貌,表明二者的比例对于体现模板转录功能的优劣具有重要意义.圆二色谱(CD)表明,形成的凝胶聚集体具有手性特征.XRD结果表明,生成的TiO2纳米材料具有锐钛矿晶型.通过光催化染料褪色实验,对所得TiO2纳米材料的光化学活性进行了初步研究.     

Asymmetric Synthesis of Overcrowded Alkenes by Transfer of Axial Single Bond Chirality to Axial Double Bond Chirality

Optically active overcrowded alkenes were synthesized by employing bis-β-naphthol as a chiral template during an intramolecular coupling reaction. The major isomer 2 has a unique helical structure with twisted and folded structural moieties. Removal of the chiral template afforded overcrowded thioxanthylidene 3 with 96 % ee, which indicates that no racemization or isomerization of the enantiomers took place.     

Glycosyl‐Templated Chiral Helix Stapling of Ethynylpyridine Oligomers by Alkene Metathesis between Inter‐Pitch Side Chains

Ethynylpyridine polymers and oligomers consisting of 4‐substituted pyridine rings linked by acetylene bonds at the 2‐ and 6‐positions have been investigated. Ethynylpyridine oligomers covalently linked with a glycosyl chiral template form chiral helical complexes by intramolecular hydrogen bonding, in which the chirality of the template is translated to the helix. With a view to fixation of the chiral architecture, D /L ‐galactosyl‐ and D /L ‐mannosyl‐linked ethynylpyridine oligomers have been developed with 4‐(3‐butenyloxy)pyridine units having alkene side chains. The helical structures are successfully stapled by alkene metathesis of the side chains. Subsequent removal of the chiral templates by acidolysis produces template‐free stapled oligomers. The chiral, template‐free, stapled oligomers show chiral helicity, which is resistant to polar solvents and heating.     

Synthesis of (+)-(1S,2R) and (−)-(1R,2S)-2-aminocyclobutane-1-carboxylic acids

(+)-(1S,2R) and (−)-(1R,2S)-2-aminocyclobutane-1-carboxylic acids have been prepared in >97% ee and in 33% and 20% overall yields starting from a single, chiral, bicyclic compound perceived as a chiral uracil equivalent. Construction of the cyclobutane ring is achieved via a [2+2] photocycloaddition reaction of this chiral precursor with ethylene.     

Kinetic resolution of 2-hydroxy-2-aryl-ethylphosphonates by a non-enzymatic acylation catalyst

Optically pure hydroxyphosphonates are widely used as derivatizable compounds that can be incorporated into a variety of synthetic strategies for the preparation of other high value organic products. A non-enzymatic kinetic resolution procedure to obtain chiral 2-hydroxy-2-arylethylphosphonates from the easily available racemic counterparts is described. A range of 2-hydroxy-2-arylethylphosphonates was efficiently resolved employing a planar-chiral DMAP derived catalyst with good selectivities (up to S=68). The chiral hydroxyphosphonates were isolated in good yields and high enantiomeric excess (>94% ee).     

Asymmetric hydroarsination reactions toward synthesis of alcohol functionalised C-chiral As–P ligands promoted by chiral cyclometallated complexes

The asymmetric hydroarsination reactions between diphenylarsine and 3-diphenylphosphanyl-but-3-en-1-ol and 2-diphenylphosphanyl-prop-2-en-1-ol have been achieved using the organopalladium complex containing ortho-metallated (R)-[1-(dimethylamino)ethylnaphthalene as the chiral reaction template in high stereoselectivities under mild conditions. Hydroarsination of 3-diphenylphosphanyl-but-3-en-1-ol with diphenylarsine generated only one stereoisomer as five-membered As–P bidentate chelate on chiral naphthylamine palladium template. Using the same chiral metal template, similar hydroarsination reaction was carried out on 2-diphenylphosphanyl-prop-2-en-1-ol which gave two different products in the ratio of 2.6 to 1. The major isomer was identified as the expected five-membered As–P bidentate ligand and the minor isomer was identified as the elimination product. The naphthylamine auxiliary could be removed chemoselectively by treatment with concentrated hydrochloric acid. Optically pure As–P ligands containing the hydroxy groups at the chiral carbon centres were prepared by ligand displacement. The absolute configuration and coordination properties of the complexes have been established by single crystal X-ray analysis.     

Asymmetric hydroarsination reactions toward synthesis of alcohol functionalised C-chiral As–P ligands promoted by chiral cyclometallated complexes

The asymmetric hydroarsination reactions between diphenylarsine and 3-diphenylphosphanyl-but-3-en-1-ol and 2-diphenylphosphanyl-prop-2-en-1-ol have been achieved using the organopalladium complex containing ortho-metallated (R)-[1-(dimethylamino)ethylnaphthalene as the chiral reaction template in high stereoselectivities under mild conditions. Hydroarsination of 3-diphenylphosphanyl-but-3-en-1-ol with diphenylarsine generated only one stereoisomer as five-membered As–P bidentate chelate on chiral naphthylamine palladium template. Using the same chiral metal template, similar hydroarsination reaction was carried out on 2-diphenylphosphanyl-prop-2-en-1-ol which gave two different products in the ratio of 2.6 to 1. The major isomer was identified as the expected five-membered As–P bidentate ligand and the minor isomer was identified as the elimination product. The naphthylamine auxiliary could be removed chemoselectively by treatment with concentrated hydrochloric acid. Optically pure As–P ligands containing the hydroxy groups at the chiral carbon centres were prepared by ligand displacement. The absolute configuration and coordination properties of the complexes have been established by single crystal X-ray analysis.     

Formation of chiral 21-helical columnar host system with phenylacetylene unit by using (1R,2S)-2-amino-1,2-diphenylethanol

A tunable supramolecular phenylacetylene host system with a chiral channel-like cavity is developed by using (1R,2S)-2-amino-1,2-diphenylethanol. This host system possesses a chiral 2₁-helical columnar structure; chiral cavities are constructed by the self-assembly of the 2₁-helical column, and guest molecules are included by varying the packing of this column.     

同时烙印分子烙印手性固定相

对采用两种对本同时烙印的方法,制备的氨基酸衍生物分子烙印手性固定相进行了考察。研究表明,如果两种烙印分子单独烙印的分子烙印手性对固定相对两种烙印分子具有较强的手性交叉拆分能力,那么这两种烙印分子同时烙印制得的分子烙印手性固定相就可对两种烙印分子均具有很好的手性分离能力,从而使专一性强的分子烙印手性固定相能同时分离多种对映体。     

Chiral N-phosphino sulfinamide ligands in rhodium(I)-catalyzed [2+2+2] cycloaddition reactions

The combination of cationic rhodium(I) complexes with N-phosphino tert-butylsulfinamides (PNSO) ligands is efficient for catalytic intra- and intermolecular [2+2+2] cycloaddition reactions. PNSO ligands are a new class of chiral bidentate ligands, which have the characteristic of combining the easily accessible sulfur chirality with the coordinating capacity of phosphorous. Cycloaddition of open-chained and macrocyclic E-enediynes with these chiral complexes have proved to be highly efficient in terms of yields, giving moderate enantiomeric excesses of the corresponding cyclohexadiene derivatives. In addition Rh(I)/PNSO complexes catalyzed the intermolecular cycloaddition of diynes with monoalkynes in mild reaction conditions and short reaction times.     

Studies in stereoselective [2+2]-cycloadditions with dichloroketene

During the investigation of the reaction of dichloroketene with cyclic enoxy-lactones and acyclic enoxy-ester substrates it was found that only the acylic variants effectively participated in the [2+2]-cycloaddition. Although a complete understanding of the reasons for this are lacking, molecular mechanics calculations do suggest that an out of plane twist of the cabonyl group in the acyclic compounds may be partially responsible. After screening a variety of chiral auxiliaries it was found that useful levels of diastereoselectivity (2.6-10.8:1) could be obtained in this cycloaddition reaction when (R)-2,2-diphenylcyclopentanol was used as the chiral auxiliary.     

手性1，4-二胺构建的双核铜[2+2]席夫碱大环化合物：制备和催化研究

Dinuclear copper(Ⅱ) complexes of [2+2] macrocyclic Schiff bases have been prepared from chiral 1,4-diamines using sodium ions as template. Catalytic investigation on the titled complexes has been carried out on model reactions (asymmetric sulfoxidation and asymmetric oxidative-coupling reactions).     

Tuning mechanism in helical columnar thiophene host system with 2-thienylacetic acid by using (1R,2S)-2-amino-1,2-diphenylethanol

A tunable supramolecular thiophene host system with a chiral channel-like cavity is developed using (1R,2S)-2-amino-1,2-diphenylethanol. This thiophene host system possesses a chiral helical columnar structure. The chiral cavities are formed by the self-assembly of the helical column, and guest molecules are included by varying the helical structure and packing arrangement of this column.     

Selective synthesis of either enantiomer of alpha-amino acids by switching the regiochemistry of the tricyclic iminolactones prepared from a single chiral source

Preparation of l-alpha-amino acids was easily accomplished simply by exchanging the position of the lactone group of our recently reported chiral template 1 from C2 to C3. The new chiral template 7 was prepared in 54% overall yield over five steps from (1R)-(+)-camphor. Alkylation of iminolactone 7 afforded the alpha-monosubstituted products in good yields and excellent diastereoselectivities (>98%). Hydrolysis of the alkylated iminolactones furnished the desired l-alpha-amino acids in good yields and ee with nearly quantitative recovery of chiral auxiliary 4.     

Reactivity of 2-halo-2H-azirines. Part 3: Dehalogenation of 2-halo-2H-azirine-2-carboxylates

The dehalogenation of 2-halo-3-phenyl-2H-azirine-2-carboxylates is described. Using sodium borohydride and tributyltin hydride 3-phenyl-2H-azirine-2-carboxylates were obtained in moderate yields. The synthesis of a new 2-bromo-2H-azirines with a chiral auxiliary, 10-phenylsulfonylisobornyl 2-bromo-3-phenyl-2H-azirine-2-carboxylate, is reported. Its dehalogenation led to 10-phenylsulfonylisobornyl 2H-azirine-2-carboxylate as single stereoisomer together with the formation of 10-phenylsulfonylisobornyl acetate.