Oil-in-alcohol highly concentrated emulsions as templates for the preparation of macroporous materials

New oil-in-alcohol highly concentrated emulsions were formulated and were used as a templates to obtain macroporous poly(furfuryl alcohol) monoliths by a one-step method. The oil-in-alcohol highly concentrated emulsions were prepared by stepwise addition of the oil phase to the surfactant-alcohol solution and were characterized by optical microscopy and by laser diffraction. The typical structure of highly concentrated emulsions, with close-packed polyhedral droplets, has been observed. Poly(furfuryl alcohol) monoliths were obtained by polymerizing in the external phase of these emulsions. These materials are mainly macroporous and retain the size distribution and morphology from the highly concentrated emulsions. The internal structure of the monoliths was observed by scanning electron microscopy. The images showed an interconnected network with pore size similar to the droplet size of the highly concentrated emulsions used as templates.     

Application of titanium catalysts for the syntheses of heterocycles

The metal catalyzed synthesis of heterocycles is becoming an important and highly rewarding protocol in organic synthesis. Traditional approaches require expensive or highly specialized equipment or would be of limited use to the synthetic organic chemist due to their highly inconvenient approaches. Titanium-mediated cyclization reactions have been recognized as some of the simplest and useful tools for regio- as well as stereoselective syntheses of five-membered N-heterocycles. This review summarizes the applications of titanium catalysts with emphasis of their synthetic applications for different heterocylces. This review covered interesting discoveries in the past few years.     

Hafnium inspired activation of highly hindered anhydrides in the acylation of alcohols and polyols

A novel and highly efficient method for activating highly hindered acid anhydrides towards the acylation of alcohols and carbohydrate-derived polyols has been developed. This new method relies on the capacity of the hafnium triflate catalyst Hf(OTf)₂ to activate highly hindered acid anhydrides, and to direct the acylation reaction. This new acylation protocol is mild and proceed at room temperature with low catalyst loading. The method is versatile and has been extended to different alcohol substrates with different steric encumbrance as well as carbohydrate-derived polyols to afford the corresponding ester products in good to excellent yields.     

微凝胶胶体晶体研究进展

Poly(N-isopropylacrylamide)(PNIPAM)微凝胶粒子是一种软的胶体粒子.和单分散的SiO_2、PS、PMMA等硬的胶体粒子一样,单分散的PNIPAM微凝胶粒子也可以自组装成为高度有序的胶体晶体.微凝胶粒子软物质的特性及其对外部刺激的响应性赋予其不同于硬球的组装行为.微凝胶胶体晶体的高度有序结构及其刺激响应性使其在诸多领域有重要用途.本文分别介绍了三维及二维微凝胶胶体晶体组装的研究进展,并对已开发的基于微凝胶胶体晶体的应用进行了总结.     

A TriPPPro-Nucleotide Reporter with Optimized Cell-Permeable Dyes for Metabolic Labeling of Cellular and Viral DNA in Living Cells

The metabolic labeling of nucleic acids in living cells is highly desirable to track the dynamics of nucleic acid metabolism in real-time and has the potential to provide novel insights into cellular biology as well as pathogen-host interactions. Catalyst-free inverse electron demand Diels–Alder reactions (iEDDA) with nucleosides carrying highly reactive moieties such as axial 2-trans-cyclooctene (2TCOa) would be an ideal tool to allow intracellular labeling of DNA. However, cellular kinase phosphorylation of the modified nucleosides is needed after cellular uptake as triphosphates are not membrane permeable. Unfortunately, the narrow substrate window of most endogenous kinases limits the use of highly reactive moieties. Here, we apply our TriPPPro (triphosphate pronucleotide) approach to directly deliver a highly reactive 2TCOa-modified 2′-deoxycytidine triphosphate reporter into living cells. We show that this nucleoside triphosphate is metabolically incorporated into de novo synthesized cellular and viral DNA and can be labeled with highly reactive and cell-permeable fluorescent dye-tetrazine conjugates via iEDDA to visualize DNA in living cells directly. Thus, we present the first comprehensive method for live-cell imaging of cellular and viral nucleic acids using a two-step labeling approach.     

Pd cluster nanowires as highly efficient catalysts for selective hydrogenation reactions

Palladium is a key catalyst invaluable to many industrial processes and fine-chemical synthesis. Although recent progress has allowed the synthesis of Pd nanoparticles with various shapes by using different techniques, the facile synthesis of Pd nanocrystals and turning them into a highly active, selective, and stable catalyst systems still remain challenging. Herein, we report the highly selective one-pot synthesis of monodisperse Pd cluster nanowires in aqueous solution; these consist of interconnected nanoparticles and may serve as highly active catalysts because of the enrichment of high index facets on the surface, including {443}, {331}, and {221} steps. For the first time, carbon nanotube and γ-Al(2)O(3) immobilized Pd cluster nanowires showed highly enhanced catalytic performance in the liquid-phase selective hydrogenation of cinnamaldehyde and gas-phase hydrogenation of 1,3butadiene relative to immobilized Pd icosahedra and nanocubes, as well as commercial Pd catalysts.     

基于环糊精的高度支化聚合物*

环糊精（CD）与高度支化聚合物都存在空腔结构,若将两者结合起来可构筑出含有两种不同疏水空腔且具有特异物理化学功能的高分子体系,并有望在分子包合与识别、药物控释、基因传输等领域得到新的应用。本文根据高度支化聚合物与环糊精结合方式的不同,从以环糊精为核的高度支化聚合物、外端悬挂环糊精的高度支化聚合物、高度支化聚合物的结构单元与环糊精包合、环糊精与客体分子包合后自组装成高度支化聚合物,以及用功能化的环糊精单体合成超支化聚合物等5个方面对其研究进展进行了总结和评述,并在此基础上展望了该类聚合物的研究方向和发展趋势。     

Complete basis set ab initio computational study of three-dimensional aromaticity in highly symmetric hydrogen clusters

The aromaticity of planar and highly symmetric three-dimensional hydrogen clusters were evaluated with the complete basis set ab initio computational method. The energy of formation of the hydrogen clusters from the hydrogen molecule and hydrogen molecular ions were used in comparison to their relative stabilities. The aromaticity of planar hydrogen clusters, as well as hydrogen clusters in the three dimensions, arranged as highly symmetric regular polyhedra (Plato's polyhedras), were discussed with respect to the Hückel and Möbius aromatic rules.     

Bifunctional cinchona alkaloids-catalyzed asymmetric [4+2] cycloaddition reaction of β,γ-unsaturated α-keto esters with oxazolones

A highly enantioselective [4+2] cycloaddition reaction of β,γ-unsaturated α-keto esters with oxazolones was realized with readily available cinchona alkaloids as the catalysts. Using this reaction, a series of highly functionalized δ-lactones with adjacent α-quaternary-β-tertiary stereocenters were obtained in high yields (up to 97%) and with good-to-excellent enantioselectivities (up to 97% ee).     

Asymmetric Mannich reaction of dicarbonyl compounds with alpha-amido sulfones catalyzed by cinchona alkaloids and synthesis of chiral dihydropyrimidones

The highly enantioselective cinchona alkaloid-catalyzed Mannich reaction of dicarbonyl compounds with alpha-amido sulfones as acyl imine precursors is described. The reaction requires 10 mol % of the cinchona alkaloid catalyst, which serves as a general base to generate acyl imines in situ, and aqueous Na2CO3 to maintain the concentration of free alkaloid catalyst. The reaction products are obtained in good yields and high enantioselectivities, and in diastereoselectivities that range from 1:1 to >95:5. The cinchonine-catalyzed reactions provide practical access to highly functionalized building blocks which have been employed in the synthesis of chiral dihydropyrimidones, a class of compounds rich in diverse biological activity. Dihydropyrimidone modifications include a highly diastereoselective hydrogenation of the enamide moiety, using an H-Cube flow hydrogenator and a Rh(II)-mediated 1,3-dipolar cycloaddition to afford highly functionalized complex heterocycles.     

Scope of palladium-catalyzed alkylative ring opening

We have explored the scope of the palladium-catalyzed nucleophilic ring opening methodology. New highly selective and highly active catalysts have been found for the ring opening of oxabenzonorbornadienes. Employing these catalysts, the addition of various alkyl nucleophiles to oxabenzonorbornadiene has been achieved. In addition, reaction of diethylzinc with [3.2.1] oxabicyclic alkenes has been accomplished to yield ring-opened products as well as functionalized alkene addition products.     

Indium-mediated regio- and diastereoselective reduction of norbornyl alpha-diketones

A novel, efficient, and regio- as well as diastereoselective conversion of non-enolizable bicyclic alpha-diketones into synthetically useful acyloins mediated by indium metal is described. The reduction is highly diastereoselective, leading exclusively to endo-acyloins (endo-hydroxyl groups) in excellent yields, and tolerates a variety of sensitive substituents, such as acetate, ester, and bridgehead halogens. The regioselectivity in the reductions of monosubstituted alpha-diketones varied from 70:30 to 100:0 for the two possible isomeric alcohols. The methodology is extended to the synthesis of highly functionalized cyclopentane carboxaldehydes, potential building blocks in organic syntheses, by cleavage of the acyloins by treating them with Pb(OAc)4 in MeOH/PhH. Allylindium additions to carboxaldehydes 22 have been found to be highly diastereoselective.     

FeCl3: an efficient catalyst for reactions of electron-rich arenes with imines or aziridines

Iron(III) chloride was discovered highly effective as catalyst in the Friedel-Crafts reactions of electron-rich arenes with imines or aziridines. It was found that reactions of imines were highly substrate-dependent, which generated mono- or double-addition products, while arenes reacted with aziridines regioselectively leading to the formation of desired ring-opening products in 2 min with moderate to good yields.     

Novel 1,3-dipolar cycloaddition reactions of calix[4]bis(spirodienones): synthesis of isoxazolidine derived macrocycles

Calix[4]bis(spirodienones) can perform as either 4π or 2π components in cycloaddition reactions with various carbo- and hetero-dienophiles and with 1,2-benzoquinones leading to the formation of highly functionalized macrocycles. In this Letter we report, highly regio- and stereoselective 1,3-dipolar cycloaddition reactions of a bis(spirodienone) derivative of calix[4]arene with nitrones that provide easy access to isoxazolidine derived macrocycles in excellent yields. These isoxazolidine derivatives can be considered as direct precursors of 1,3-amino alcohols.     

De novo asymmetric syntheses of muricatacin and its analogues via dihydroxylation of dienoates

A short and highly efficient route to both enantiomers of muricatacin as well as the C-5-epimer has been developed. The key to the overall transformation is the highly regio- and enantioselective Sharpless asymmetric dihydroxylation of an (E,Z)-dienoate. The highly efficient stereoselective synthesis prepares (-)-muricatacin in seven steps and 66% overall yield.     

High performance "ionic liquid" chromatography

We firstly developed high performance liquid chromatography methods with "ionic liquids" as eluents (HPILC) and successfully demonstrated the analysis of various biopolymers including scarcely soluble highly polymerized cellulose by means of HPILC with highly polar ionic liquid.     

Asymmetric cycloadditions of palladium-polarized aza-o-xylylenes

Vinyl benzoxazinanones undergo highly enantioselective decarboxylative cycloadditions with electron-deficient olefins in the presence of palladium catalysts. Palladium induces the decarboxylation of the parent benzoxazinanones under mild conditions to produce an intermediate that can be described as a polarized aza-o-xylylene. These intermediates undergo a formal [4 + 2] cycloaddition with good Michael acceptors to produce highly substituted hydroquinolines with excellent regio-, diastereo-, and enantioselectivities.     

Highly enantio- and diastereoselective organocatalytic cascade aza-Michael-Michael reactions: a direct method for the synthesis of trisubstituted chiral pyrrolidines

An unprecedented highly enantio- and diastereoselective cascade aza-Michael-Michael reaction of alpha,beta-unsaturated aldehydes with trans-gamma-Ts protected amino alpha,beta-unsaturated ester has been developed; the simple and practical process, efficiently catalyzed by chiral diphenylprolinol TMS ether, serves as a powerful access to highly functionalized trisubstituted chiral pyrrolidines.     

Enantioselective nitroaldol reaction of alpha-ketoesters catalyzed by cinchona alkaloids

The development of highly enantioselective and general catalytic nitroaldol (Henry) reactions with ketones is a challenging yet desirable task in organic synthesis. In this communication, we report an asymmetric nitroaldol reaction with alpha-ketoesters catalyzed by a new C6'-OH cinchona alkaloid catalyst. This is the first highly efficient organocatalytic asymmetric Henry reaction with ketones. This reaction is operationally simple and affords high enantioselectivity as well as good to excellent yield for a broad range of alpha-ketoesters.     

Microfibers as Physiologically Relevant Platforms for Creation of 3D Cell Cultures

Microfibers have received much attention due to their promise for creating flexible and highly relevant tissue models for use in biomedical applications such as 3D cell culture, tissue modeling, and clinical treatments. A generated tissue or implanted material should mimic the natural microenvironment in terms of structural and mechanical properties as well as cell adhesion, differentiation, and growth rate. Therefore, the mechanical and biological properties of the fibers are of importance. This paper briefly introduces common fiber fabrication approaches, provides examples of polymers used in biomedical applications, and then reviews the methods applied to modify the mechanical and biological properties of fibers fabricated using different approaches for creating a highly controlled microenvironment for cell culturing. It is shown that microfibers are a highly tunable and versatile tool with great promise for creating 3D cell cultures with specific properties.