聚合物支载的硼氢化钠还原剂系统对苯乙酮的不对称还原

聚合物支载硼氢负离子还原剂Na^+[P-COO(BH~3)]^-中的活泼氢原子能用于酮的不对称还原。该试剂中加入带手性碳的羧酸或醇, 反应后生成的还原系统还原苯乙酮。     

天然海洋环酯肽Stereocalpin A中间体的合成

以D-苯丙氨酸为原料,经过硼氢化钠/碘还原后与三光气在碱性条件下环合得到Evans手性助剂(R)-4-苄基-2-噁唑烷酮(2),然后将其与丙酰氯缩合,经过LDA偶联、反式Aldol等反应,合成了天然环酯肽StereocalpinA中含有的独特结构片段,该片段对3种人实体瘤细胞系(HT-29,B16/F10,HepG2)具有中等细胞毒性,总收率为30.6%。结果表明,合成路线简便可行,反应产率高,立体选择性好。是制备该化合物的有效途径。     

Preparation of Polymer-Supported Chiral 1,2-Diamine as an Efficient Ligand for Asymmetric Hydrogenation Catalyst

An enantiopure 1,2-diamine having two phenolic hydroxy groups was synthesized, and attached to chloromethylated poly(styrene) through a benzyl ether linkage. The polymer-supported Ru precatalysts were prepared from the polymeric chiral 1,2-diamine and RuCl₂/BINAP complex. In the presence of t-BuOK the polymeric catalyst system worked well in asymmetric hydrogenation of aromatic ketones in a mixed solvent of 2-propanol and DMF. The insoluble polymeric catalyst was readily separated from the reaction mixture and reused at least several times without loss of the catalytic activity.     

S-Substituted-2-mercaptobenzthiazolium-based chiral ionic liquids: efficient organocatalysts for enantioselective sodium borohydride reductions of prochiral ketones

Novel chiral ionic liquids having chirality in their cationic part have been synthesized for evaluation of their catalytic potential as organocatalysts in sodium borohydride reduction of prochiral ketones to yield optically active secondary alcohols. The chiral ionic liquids have been synthesized from the reaction of (?)-menthol or (?)-borneol, chloroacetic acid and S-methyl/benzyl-2-mercaptobenzthiazole. The synthesized chiral ionic liquids have been characterized by ¹H, ¹³C NMR and Mass spectrometry. Moderate to excellent enantiomeric excess (ee > 99%) has been obtained in asymmetric sodium borohydride reduction of prochiral ketones using these salts as chiral catalysts.     

Use of poly(sodium oleyl-L-leucylvalinate) surfactant for the separation of chiral compounds in micellar electrokinetic chromatography

A chiral amino acid-based monomeric and polymeric surfactant, sodium oleyl-L-leucylvalinate) (L-SOLV) and poly(sodium oleyl-L-leucylvalinate) (poly-L-SOLV) were synthesized and used for chiral separations in micellar electrokinetic chromatography (MEKC). Poly-L-SOLV was used successfully in the separation of various enantiomers of neutral, acidic, and basic analytes such as 1,1'-bi-2-napthol, 1,1'-binaphthyl-2,2'-diamine, benzoin, hydrobenzoin, benzoin methylether, warfarin, and coumachlor obtaining well-resolved peaks but with only partial separation of temazepam. In addition, the atropisomer 1,1'-binaphthyl-2, 2'-dihydrogen phosphate was chosen to study the applicability of the polymeric surfactant over a wide range of parameters such as concentration, temperature, voltage, and pH. The most striking characteristic of this new surfactant is its high hydrophobicity. It is favorable to interactions with hydrophobic chiral analytes, and thus may provide better chiral recognition for the compounds.     

Chiral separation of polychlorinated biphenyls using a combination of hydroxypropyl-gamma-cyclodextrin and a polymeric chiral surfactant

Chiral separation of moderately to highly hydrophobic polychlorinated biphenyls (PCBs) using a conventional chiral micelle or a polymeric chiral surfactant, as the single chiral selector is very difficult since the hydrophobic interactions between the chiral PCB and the monomeric or polymeric surfactant is very strong. Combined use of a polymeric chiral surfactant, polysodium N-undecanoyl-D-valinate (poly-D-SUV) with hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD) was successful in cyclodextrin modified electrokinetic chromatography (CD-EKC) enantioseparation of PCB congeners. Addition of HP-gamma-CD to the background electrolyte containing poly-D-SUV functioned to improved chiral resolution for the PCBs and reduce the analysis time for these congeners. In addition, concentration of methanol, concentration of 2-(N-cyclohexylamino) ethanesulfonic acid (CHES) buffer and separation voltage was also varied to optimize multicomponent separation of five chiral PCBs. Simultaneous separation and enantioseparation of all five PCBs was possible in less than 50 min under optimized conditions that requires a 5 mM CHES solution buffered at about pH 10 with 1.5% w/v (ca. 60 mM) poly-D-SUV and 16 mM HP-gamma-CD. In addition, 1 M urea and 20% v/v methanol should be added as organic modifier and the capillary temperature maintained at 45 degrees C. As expected the polymeric surfactant showed improved chiral resolution of PCBs over conventional micelles of SUV. Under optimized conditions, when CD-EKC of chiral PCBs using poly-D-SUV was compared to sodium dodecyl sulfate (SDS), better resolution, higher efficiency and shorter analysis time was achieved with poly-D-SUV.     

Chiral bisphosphine BINAP-stabilized gold and palladium nanoparticles with small size and their palladium nanoparticle-catalyzed asymmetric reaction

The reduction of tetrachloroaurate or potassium tetrachloropalladate with sodium borohydride in the presence of optically active 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl [BINAP] gave the chiral (S)- or (R)-BINAP-stabilized gold or palladium nanoparticles which showed the small core (1.7 nm for BINAP-Au and 2.0 nm for BINAP-Pd) with narrow size distribution and remarkably high stability. Asymmetric hydrosilylation of styrene with trichlorosilane in the presence of chiral BINAP-Pd nanoparticles afforded an optically active 1-phenyl-1-trichlorosilylethane which was converted into an optically active 1-phenylethanol (95% enantiomeric excess) by oxidative cleavage of the carbon-silicon bond.     

Preparation of the enantiopure 1,2-diamine monomer and its polymerization: The efficient polymeric chiral ligand of an asymmetric hydrogenation catalyst

An enantiopure 1,2-diamine monomer possessing a p-vinylbenzyl group as a polymerizable group was synthesized from chiral 1,2-bis(p-hydroxyphenyl)-N,N′-bis(tert-butoxycarbonyl)-1,2-diaminoethane. The chiral monomer was copolymerized with styrene, and this was followed by the deprotection of the tert-butoxycarbonyl group, which yielded the polymer-supported chiral 1,2-diamine. The polymeric catalyst system was established with the polymeric chiral 1,2-diamine complexed with 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl/RuCl₂. In the presence of potassium tert-butoxide (t-BuOK), the polymeric catalyst system worked well in the asymmetric hydrogenation of aromatic ketones. The corresponding chiral secondary alcohols were obtained in quantitative yields with a high level of enantioselectivity. The insolubility of the catalyst, caused by the crosslinked structure of the polymer, made it recyclable. The polymeric catalyst was reused several times without a loss of catalytic activity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4556–4562, 2004     

Asymmetric Mukaiyama aldol reaction of silyl enol ethers with aldehydes using a polymer-supported chiral Lewis acid catalyst

Chiral N-sulfonylated α-amino acid monomer (5) derived from (S)-tryptophan was copolymerized with styrene and divinylbenzene under radical polymerization conditions to give a polymer-supported N-sulfonyl-(S)-tryptophan (6). Treatment of the polymer-supported chiral ligand with 3,5-bis(trifluoromethyl)phenyl boron dichloride afforded a polymeric Lewis acid catalyst (16) effective for asymmetric Mukaiyama aldol reaction of silyl enol ethers and aldehydes. Various aldehydes were allowed to react with silyl enol ethers in the presence of the polymeric chiral Lewis acid to give the corresponding aldol adducts in high yield with high levels of enantioselectivity.     

Enantioselective reduction of α-substituted ketones mediated by the boronate ester TarB-NO2

A facile and mild reduction procedure is reported for the preparation of chiral secondary alcohols prepared from α-substituted ketones using sodium borohydride and the chiral boronate ester (l)-TarB-NO₂. Direct reduction of substituted ketones bearing Lewis basic heteroatoms generally provided secondary alcohols of only modest enantiomeric excess likely due to either competition between the target carbonyl and the functionalized sidechains at the Lewis acidic boron atom in TarB-NO₂ or the added steric bulk of the α-sidechain. As an alternative method, these substrates were synthesized using TarB-NO₂ via a two-step procedure involving the reduction of an α-halo ketone to a chiral terminal epoxide, followed by regioselective/regiospecific epoxide opening by various nucleophiles. This procedure provides access to a variety of functionalized secondary alcohols including β-hydroxy ethers, thioethers, nitriles, and amines with enantiomeric excesses of 94% and yields up to 98%.     

一个手性配体的合成及其在钯催化苯乙烯的不对称氢酯基化中的诱导作用

不对称氢酯基化反应是不对称羰基化反应的一部分，与不对称氢甲酰化反应一样是产生多种手性分子的有力手段，比如重要的非麻醉性镇痛消炎药S-布洛芬、S-萘普生就可以通过芳香类烯烃的不对称氢酯基化反应来合成．在不对称羰基化中人们对不对称氢甲酰化的研究较为广泛，并取得了     

Synthesis of Novel Polymers with a Chiral 1,2-Diamine Moiety by Polycondensation and their Application to Catalyst for Asymmetric Hydrogenation of Aromatic Ketones

Summary: Novel polymers with chiral 1,2-diamine moiety were successfully synthesized by polycondensation of N-Boc protected enantiopure 1,2-diamine bearing two phenol groups ( S , S )-4 , bisphenol derivatives, and dibromides, followed by deprotection of N-Boc moiety. Hydrogenation of acetophenone was performed with use of polymeric catalyst system prepared from the polymer-supported chiral 1,2-diamine and RuCl₂/(S)-BINAP. The reaction proceeded smoothly even in 2-propanol to give 1-phenylethanol in quantitative yield with high level of enantioselectivity. Furthermore, various other aromatic ketones could be asymmetrically hydrogenated by the polymeric catalyst system.     

Poly(dimethylamino)ethyl methacrylate for use as a surfactant in the miniemulsion polymerization of styrene

A novel Y-shaped macromonomer based on poly[(dimethylamino)ethyl methacrylate] (PDMAEMA) with a narrow molecular weight distribution was synthesized via oxyanion-initiated polymerization in which a potassium alcoholate of trimethylol propane allyl ether (2K-TMPAE) was used as a difunctional initiator. For the miniemulsion polymerization of styrene, this macromonomer acted well both as a comonomer carrying a reactive C=C double bond in its central section and as a pH-responsive polycationic surfactant in media with different pH values. The resulting microspheres composed of a hydrophobic polystyrene core and a hydrophilic PDMAEMA-protonated corona have shown spherical morphology and are quite stable. The nature of the reactive group, the amount of polymeric surfactant, and pH values in the aqueous medium have been systematically investigated during the miniemulsion polymerization by analyzing the evolution of the monomer conversions. The results of FTIR and (1)H NMR spectra demonstrated the generation of the functional particles. The analyses of TEM micrographs and dynamic light scattering (DLS) confirmed that the latices had a relatively narrow particle size distribution. The measurement of the zeta potential gave further evidence of the "hairy" particle structure. Because the reactive group is located in the central section of the macromonomer, the stabilization mechanism of the polymeric surfactant can be ascribed to (1) the absorption of two polycationic and hydrophilic tails that have electrostatic and steric stabilization to decrease the interface tension and (2) the copolymerization with the styrene monomer.     

Synthesis and characterization of water‐soluble barbiturate‐ and thiobarbiturate‐functionalized polystyrene

The synthesis and characterization of barbiturate‐ and thiobarbiturate‐functionalized polystyrene from polystyrene homopolymer by polymer‐modification reactions is discussed. Polystyrene homopolymer quantitatively functionalized at the para postion with diethyl oxomalonate functionality was subjected to a condensation reaction with urea and thiourea in the presence of sodium methoxide in methanol. This reaction proceeded essentially to quantitative conversion to the barbiturate‐ (BAPS) and thiobarbiturate‐functionalized polystyrenes (TBAPS) as estimated by ¹H NMR, UV, and IR spectroscopies. Thus, several copolymers of styrene with barbiturate‐ and thiobarbiturate‐functionalized styrene were synthesized. The detailed characterizations of quantitatively functionalized polystyrene using gel permeation chromatographic, IR, UV, and ¹H NMR spectroscopic techniques as well as thermogravimetric analysis are discussed. An application of the newly synthesized polymer in removing Cu(II) ions from aqueous solution is demonstrated. This is the first report on the synthesis of BAPS and TBAPS by the polymer‐modification route or otherwise. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 731–737, 2002; DOI 10.1002/pola.10154     

Asymmetric synthesis of (alphaR)-polyfluoroalkylated prolinols based on the perfluoroalkyl-induced highly stereoselective reduction of perfluoroalkyl N-Boc-pyrrolidyl ketones

Reduction of the obtained chiral (S)- tert-butyl 2-(perfluoroalkanoyl)pyrrolidine-1-carboxylate with sodium borohydride or lithium aluminum hydride proceeded smoothly to give the corresponding (S)- tert-butyl 2-((R)-perfluoro-1-hydroxyalkyl)pyrrolidine-1-carboxylate in yields of 73-97% with excellent diastereoselectivities (up to >98% de), compared with the reduction of nonfluorinated (S)-tert-butyl 2-pentanoylpyrrolidine-1-carboxylate.     

用多官能团引发剂合成超支化聚苯乙烯及其C60衍生物

通过α-溴丙酰溴与Z5(季戊四醇与2,2-二羟甲基丙酸缩聚的产物)酯化反应制得超支化原子转移自由基聚合(ATRP)引发剂Z5-B(约含19个引发点).在100℃及CuCl/N,N,N,N",N"-五甲基二亚乙基三胺催化下,用Z5-B引发苯乙烯的ATRP聚合(环己酮为溶剂,体积分数为50%),得到超支化的聚苯乙烯,将溴端基叠氮化后与C60反应,获得超支化聚苯乙烯C60衍生物.该超支化C60衍生物可用于光限制材料.     

Synthesis of 4‐tert‐butyldimethylsilyloxystyrene and its copolymerization with styrene using (η5‐indenyl)trichlorotitanium in the presence of methylaluminoxane

Poly(styrene‐co‐4‐tert‐butyldimethylsilyloxystyrene) as a precursor of hydroxyl‐functionalized syndiotactic polystyrene was successfully synthesized via (η⁵‐indenyl)trichlorotitanium (IndTiCl₃)‐catalyzed copolymerization of styrene with 4‐tert‐butyldimethylsilyloxystyrene in toluene at 25°C in the presence of methylaluminoxane (MAO) ([Al]/[Ti] = 2 000). The amount of styrene derivative incorporated into the polymeric chain for a 20,7 : 1 mole feed ratio of styrene to 4‐tert‐butyldimethylsilyloxystyrene was found to be 1,8 mol‐% from a ¹H NMR analysis. The styrene derivative was successfully prepared from 4‐hydroxybenzaldehyde via first protecting the hydroxyl group using tert‐butyldimethylchlorosilane followed by the ‘Wittig‐type’ reaction with the ‘Tebbe’ reagent. The yield was about 82 wt.‐% on the basis of the initial amount of 4‐hydroxybenzaldehyde used.     

苷类化合物研究(Ⅰ)——天麻苷类似物的合成

本文合成了16种天麻苷类似物,测定了它们的¹³CNMR和¹HNMR。依据NMR数据,这些化合物的端基构型指定为β构型。     

Copolymerized polymeric surfactants: characterization and application in micellar electrokinetic chromatography

An achiral monomeric surfactant (sodium 10-undecenyl sulfate, SUS) and a chiral surfactant (sodium 10-undecenoyl L-leucinate, SUL) were synthesized and polymerized individually to form poly-SUS and poly-SUL. These surfactants were then copolymerized at various molar ratios to produce a variety of copolymerized surfactants (CoPSs), possessing both achiral (sulfate) and chiral (leucinate) head groups. The CoPSs, poly-SUS, poly-SUL, and sodium dodecyl sulfate were characterized using several analytical techniques. The aggregation numbers of the polymeric surfactants and the partial specific volumes were determined by the use of fluorescence quenching and density measurements, respectively. These polymeric surfactants were investigated as novel pseudostationary phases in micellar electrokinetic chromatography (MEKC) for the separation of chiral and achiral solutes. Solute hydrophobicity was found to have major influence on the MEKC retention of alkyl phenyl ketones. In contrast, hydrogen-bonding ability of benzodiazepines is the major factor that governs their retention, but hydrophobicity has an insignificant effect on MEKC retention of benzodiazepines.     

Polymer-supported N-heterocyclic carbene-palladium complex for heterogeneous Suzuki cross-coupling reaction

Poly(1-methylimidazoliummethyl styrene)-surface grafted-poly(styrene) resin was prepared for the first time as a polymer-supported N-heterocyclic carbene (NHC) precursor for palladium complex by suspension polymerization. To prepare this polymer-supported NHC precursor, 1-methyl-3-(4-vinylbenzyl)imidazolium hexafluorophosphate, [MVBIM][PF6-], was synthesized as a monomer and copolymerized with styrene and DVB in water. This polymer-supported NHC precursor with imidazolium as a ligand, which exists solely on the surface of the resin, was well characterized by FE-SEM, CLSM, and IR spectroscopy. The precursor containing imidazolium readily formed a stable complex with Pd(OAc)2, and this polymer-supported N-heterocyclic carbene-palladium complex exhibited excellent catalytic activity for Suzuki cross-coupling reaction in an aqueous medium. The catalyst was recovered quantitatively from the reaction mixture by simple filtration and was able to be reused for a number of recycles with consistent activity in all of the coupling reactions.