Abstract The synthesis, characterization and applications of heteroatom‐substituted group 4 bis(indenyl)metallocene complexes is reviewed. In recent years, an increasing number metallocenes with electronically modified cyclopentadienyl ligands have been reported with, in some cases, considerably altered catalytic properties. This microreview focuses on bis(indenyl) titanium, zirconium hafnium that contain nitrogen, oxygen sulfur atoms directly bonded to the five‐ or six‐membered rings...

The migration of acetyl, pivaloyl, and benzoyl protective groups their relative stabilities at variable pH for a series β-d-galactopyranoses were studied by NMR spectroscopy. clockwise counterclockwise rates the different ester accurately determined use kinetic model. results presented provide new insights into acid base commonly used protecting phenomenon acyl group may prove useful in planning synthesis strategies.

Abstract The substrate scope in the dynamic kinetic resolution ofsecondary alcohols was studied by using 31 structurallydifferent and isopropenyl acetate presence ofdicarbonylchlorido(pentabenzylcyclopentadienyl)rutheniumand Candida antarctica lipase B (Novozym 435, CAL‐B) toluene. enzyme ruthenium complex were shown to function a highly compatible manner allowing conversion of racemic into ( R )‐acetates practically theoretical yields and, most cases, ee values exceeding 99 %. results are...

Abstract Heterogeneously catalyzed one‐pot reactions combining individual reaction steps into sequences enhance the efficiencies of overall chemical processes by reducing costs, time, and labor efforts. This minireview focuses on production chiral compounds using dynamic kinetic resolution (DKR) related sequential reactions, utilizing heterogeneous immobilized metal catalysts enzymes. Enzymes, especially lipases, often possess high chemical, stereo‐, regiospecificities under mild conditions....

Acetylated oligosaccharides are common in nature. While they involved several biochemical and biological processes, the role of acetyl groups complexity their migration has largely gone unnoticed. In this work, by combination organic synthesis, NMR spectroscopy quantum chemical modeling, we show that group is a much more complex phenomenon than previously known. By use synthetic oligomannoside model compounds, demonstrate, for first time, polysaccharides may not be limited to transfer within...

A simple and highly efficient iron-catalyzed method for the chlorination of silanes has been developed. By use 0.5–2% Fe(III)-based catalyst FeCl3 or Fe(acac)3 in presence 1–1.5 equiv acetyl chloride as chlorine donor, a large number silanes, alkoxysilanes, silanols were converted to corresponding chlorosilanes 50–93% yields. In contrast earlier reported methods often suffering from expensive catalysts stoichiometric metal salts, hazardous reagents, reaction conditions, presently described...

The influence of siloxy substitution ethylene-bridged bis(indenyl)- and bis(tetrahydroindenyl)zirconium dichlorides on ethylene/α-olefin copolymerization ethylene homopolymerization performance was investigated. Ethylene copolymerized with 1-hexene 1-hexadecene over rac-[ethylenebis(1-(tert-butyldimethylsiloxy)-3-indenyl)]zirconium dichloride (1), rac-[ethylenebis(1-(tert-butyldimethylsiloxy)-4,5,6,7-tetrahydro-3-indenyl)]zirconium (H1),...

Development of reaction sequences that utilize renewable resources, such as carbohydrates, starting material is topical interest. Particularly attractive are protocols where unprotected mono- and oligosaccharides applied. Herein, selected approaches for direct derivatization carbohydrates highlighted. Ultimately, methodologies also applicable natural polysaccharides resulting in rapid development novel functional biobased materials future applications. 1 Introduction 2 Reacting Unprotected...

The preparation and crystal structure of the first group 4 ansa-metallocene with an oxygen atom directly bonded to 2-position η5-indenyl moiety, rac-[ethylenebis(2-(tert-butyldimethylsiloxy)indenyl)]zirconium dichloride (3), is reported. In combination methylaluminoxane (MAO), complex 3 polymerizes propylene highly isotactic crystalline polypropylene (Tm = 148 °C; Mw 19 000; Mw/Mn 2.4). Under similar conditions, polymerization activity 3/MAO exceeds that conventional catalyst system...

The solution-state conformations of various galactose derivatives were determined by comparison the experimental (1)H-(1)H vicinal coupling constants to those calculated using density functional theory (DFT) at B3LYP/cc-pVTZ//B3LYP/6-31G(d,p) level theory. agreement between and for 1,2:3,4-di-O-isopropylidene-alpha-d-galactopyranose was good, thereby confirming an (O)S(2) skew conformation it its on basis their similar observed couplings. Single-crystal X-ray analysis...

Ethylene and propylene were polymerized over the siloxy-substituted bis(indenyl) ansa-metallocenes, rac-[ethylenebis(2-(tert-butyldimethylsiloxy)indenyl)]zirconium dichloride (1), rac-[ethylenebis(2-(tert-butyldimethylsiloxy)-4,5,6,7-tetrahydroindenyl)]zirconium (2), rac-[ethylenebis(2-(tert-butyldimethylsiloxy)indenyl)]hafnium (3), using methylaluminoxane (MAO) trityl tetrakis(pentafluorophenyl)borate as cocatalysts. Especially complex 1 forms a highly active catalyst precursor for...

Abstract β‐(1→2)‐Linked oligomannosides constitute an important class of carbohydrate structures located on the cell surface several Candida species, including C. albicans . As a result immunostimulating properties such compounds, upscaling their synthesis is relevant. In this paper, highly stereoselective β‐(1→2)‐linked was performed by further development and modifications to methodologies described earlier in literature. addition fully deprotected mannobiose mannotriose, some preliminary...

Abstract Galactoglucomannan (GGM) is a polysaccharide mainly consisting of mannose, glucose, and galactose. GGM the most abundant hemicellulose in Norway spruce ( Picea abies ), but also found cell wall flax seeds, tobacco plants, kiwifruit. Although several applications for polysaccharides have been developed pulp paper manufacturing food medical industries, attempts to synthesize study distinct fragments this not reported previously. Herein, synthesis one core trisaccharide units together...

A simple iron- and silyl chloride catalyzed method for the preparation of symmetrical nonsymmetrical ethers is presented. Various aldehydes ketones were reductively etherified by using triethylsilane as a reducing agent in presence 2 mol% iron(III) oxo acetate 8 chloro(trimethyl)silane. The reactions can be carried out at ambient temperatures pressures with ethyl solvent.

Acyl group migration affects the synthesis, isolation, manipulation and purification of all acylated organic compounds containing free hydroxyl groups, in particular carbohydrates. While several isolated studies on phenomenon different buffers have been reported, comprehensive insights into overall process monosaccharides under similar conditions lacking. Here, we studied acyl using five groups by a combination experimental, kinetic theoretical tools. The results show that anomeric...

Abstract Dicarbonylchloro(pentabenzylcyclopentadienyl)ruthenium has been prepared and its structure confirmed by X‐ray analysis. This complex shows excellent catalytic activity modest stability against air in racemization reactions of secondary alcohols. In Candida antarctica lipase B (CAL‐B) catalyzed dynamic kinetic resolution (DKR) 1‐phenyl‐ 1‐(furan‐2‐yl)ethanol compounds, the new improved performance as an alcohol catalyst comparison with well‐known pentaphenylcyclopentadienyl analogue,...