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The reaction of pentamethylcyclopentadienyl titanium trichloride (Cp*TiCl3) with lithium N,N-bis{6-[2-(diethylboryl)phenyl]pyridyl-2-yl}amide resulted in the formation of chlorido[η3-N-{6-[2-(diethylboryl)phenyl]pyridyl-2-yl}-N-(6-C6H4)pyrid-2-yl)amido]pentamethylcyclopentadienyltitanium (Ti-1). The structure of Ti-1 was elucidated by using single-crystal XRD. The same compound is formed upon the reaction of Cp*TiCl3 with lithium N-{6-[2-(diethylboryl)phenyl]pyridyl-2-yl}-N’-[6-(2-bromophenyl)pyridyl-2-yl]amide. The reaction of N,N-bis[6-(2-bromophen-1-yl)pyrid-2-yl]amine (4) with lithium hexamethyldisilazide followed by the addition of Cp*TiCl3 leads to the formation of [N,N-bis{6-(2-bromophen-1-yl)pyrid-2-yl}amide]dichloridopentamethylcyclopentadienyltitanium (Ti-2). The reaction of Ti-1 with benzylmagnesium chloride yields the pentamethylcyclopentadienyl titanium vinyl complex pentamethylcyclopentadienyl{N-(6-phenylpyridyl-2-yl)-N-[6-(2-ethyl-η2-vinylboryl-C6H4)pyrid-2-yl]amido}titanium (Ti-3) by C−H activation; Ti-3 is best described as a monosubstituted titanacyclopropane. Upon activation with methylaluminoxane (MAO), Ti-1 produces linear, high-density polyethylene with molecular weights >6×106 g mol−1, whereas Ti-2 yielded ethyl-branched polyethylene. Both Ti-1 and Ti-2 are able to copolymerize ethylene (E) with norborn-2-ene (NBE) and E with cyclopentene (CPE) and to terpolymerize E with NBE and CPE. Ti-1 activated by MAO is also active in the ring-opening metathesis polymerization of NBE to produce up to 97 % cis-syndiotactic poly(NBE). The polymer structure of all resulting homo- and copolymers was elucidated by using 13C NMR spectroscopy.

Al-F-Bindungen gehoren zu den starksten bekannten σ-Bindungen und weisen sogar hohere Bindungsenergien als Si-F-Bindungen auf. Trotz eines Stabilitatsvorteils und einer potenziell hohen Lewis-Aciditat von Al-F-Komplexen, wurden diese bisher nicht als strukturell definierte Katalysatoren fur enantioselektive Reaktionen beschrieben. Hier zeigen wir, dass Al-F-Salen-Komplexe mit gekoppelten Ammonium-Einheiten eine ausergewohnlich hohe katalytische Aktivitat in asymmetrischen Carboxycyanierungen aufweisen. Neben aromatischen Aldehyden wurden auch Enale und aliphatische Substrate effizient umgesetzt. Umsatzzahlen bis zu ca. 104 wurden erreicht, wohingegen sie mit vorherigen Katalysatoren ublicherweise im Bereich von 101–102 lagen. Anders als Al-Me- und Al-Cl-Salen-Komplexe sind die analogen Al-F-Spezies bemerkenswert stabil gegenuber Luft, Wasser und Hitze, und sie konnten nach der Katalyse unverandert zuruckgewonnen werden. Sie zeichnen sich laut DFT-Rechnungen durch eine betrachtlich erhohte Lewis-Aciditat aus.

Al−F bonds are among the most stable σ bonds known, exhibiting an even higher bond energy than Si−F bonds. Despite a stability advantage and a potentially high Lewis acidity of Al−F complexes, they have not been described as structurally defined catalysts for enantioselective reactions. We show that Al−F salen complexes with appended ammonium moieties give exceptional catalytic activity in asymmetric carboxycyanations. In addition to aromatic aldehydes, enal and aliphatic substrates are well accepted. Turnover numbers up to around 104 were achieved, whereas with previous catalysts 101–102 turnovers were typically attained. In contrast to Al−Me and Al−Cl salen complexes, the analogous Al−F species are remarkably stable towards air, water, and heat, and can be recovered unchanged after catalysis. They possess a considerably increased Lewis acidity as shown by DFT calculations.

Azulenes and crystal-smectic E-phases (SmE) both have recently raised attention for the design of novel organic devices. However, the combination of self-assembly into soft-crystalline mesophases with the unique electronic properties of azulene derivatives has not been probed yet. Therefore, a convenient synthesis of 6-alkoxy-2-bromoazulenes, forming ambient temperature SmE-phases, was developed. Differential scanning calorimetry, polarising optical microscopy and X-ray diffraction provided insight into the self-assembly of the liquid crystalline phase. Comparison of experimental data and quantum chemical calculations of 6-alkoxy-2-bromoazulene with the ‘inverted’ 2-alkoxy-6-bromoazulene revealed large differences in polarity, which affected optical and mesomorphic properties, and provided insight into structure–property relationships enabling the design of novel thin-film devices.

Pulsed Electric Fields, a known technique for permeabilization of cell membranes, can considerably foster intracellular component extraction from microalgae. However, it is currently uncertain in what way, apart from the cell membrane, the cell wall is affected during pulsation. In this study, fresh Auxenochlorella protothecoides and Chlorella vulgaris were subjected to treatment with pulsed electric fields and energy input of 1.5 MJ/kgDryWeight. Subsequently the biomass was fed into a High Pressure Homogenizer for 5 passes at 1500 bar. The percentage of intact cells after each pass was determined through cell counting and compared with Control biomass that underwent the same homogenization. No major difference on the disruption degree of pulsed and control samples was observed, indicating that the resistance to mechanical stress of the cell, a function of the cell wall, is not affected by pulsed electric fields. Scanning Electron Microscopy observation also showed no superficial or structural cell alteration after pulsation.

Pulsed electric field (PEF) was conducted for the extraction of proteins/C-Phycocyanins from Arthrospira platensis. The cyanobacterial suspension was treated with 1 µs long pulses at an electric field strength of 40 kV·cm−1 and a treatment energy of 114 kJ·kgsus−1 and 56 kJ·kgsus−1. For benchmarking, additional biomass was processed by high pressure homogenization. Homogeneity of the suspension prior to PEF-treatment influenced the protein/C-phycocyanin extraction efficiency. Stability of C-Phycocyanin during post-PEF incubation time was affected by incubation temperature and pH of the external medium. Biomass concentration severely affect proteins/C-Phycocyanins extraction yield via PEF-treatment. The optimum conditions for extraction of proteins/C-Phycocyanin was obtained at 23 °C while incubating in pH 8-buffer. The energy demand for PEF-treatment amounts to 0.56 MJ·kgdw−1 when processing biomass at 100 gdw·kgsus−1. PEF treatment enhances the protein/C-Phycocyanin extraction yield, thus, it can be suggested as preferential downstream processing method for the production of C-Phycocyanin from A. platensis biomass.

The synthesis of macrocycles is severely impeded by concomitant oligomer formation. Here, we present a biomimetic approach that utilizes spatial confinement to increase macrocyclization selectivity in the ring-closing metathesis of various dienes at elevated substrate concentration up to 25 mM using an olefin metathesis catalyst selectively immobilized inside ordered mesoporous silicas with defined pore diameters. By this approach, the ratio between macro(mono)cyclization (MMC) product and all undesired oligomerization products (O) resulting from acyclic diene metathesis polymerization was increased from 0.55, corresponding to 35% MMC product obtained with the homogeneous catalyst, up to 1.49, corresponding to 60% MMC product. A correlation between the MMC/O ratio and the substrate-to-pore-size ratio was successfully established. Modification of the inner pore surface with dimethoxydimethylsilane allowed fine-tuning the effective pore size and reversing surface polarity, which resulted in a further increase of the MMC/O ratio up to 2.2, corresponding to >68% MMC product. Molecular-level simulations in model pore geometries help to rationalize the complex interplay between spatial confinement, specific (substrate and product) interaction with the pore surface, and diffusive transport. These effects can be synergistically adjusted for optimum selectivity by suitable surface modification.

Enzymes are Nature's polyfunctional catalysts tailor-made for specific biochemical synthetic transformations, which often proceed with almost perfect stereocontrol. From a synthetic point of view, artificial catalysts usually offer the advantage of much broader substrate scopes, but stereocontrol is often inferior to that possible with natural enzymes. A particularly difficult synthetic task in asymmetric catalysis is to overwrite a pronounced preference for the formation of an inherently favored diastereomer; this requires a high level of stereocontrol. In this Article, the development of a novel artificial polyfunctional catalyst type is described, in which an imidazolium-aryloxide betaine moiety cooperates with a Lewis acidic metal center (here Cu(II)) within a chiral catalyst framework. This strategy permits for the first time a general, highly enantioselective access to the otherwise rare diastereomer in the direct 1,4-addition of various 1,3-dicarbonyl substrates to β-substituted nitroolefins. The unique stereocontrol by the polyfunctional catalyst system is also demonstrated with the highly stereoselective formation of a third contiguous stereocenter making use of a diastereoselective nitronate protonation employing α,β-disubstituted nitroolefin substrates. Asymmetric 1,4-additions of β-ketoesters to α,β-disubstituted nitroolefins have never been reported before in literature. Combined mechanistic investigations including detailed spectroscopic and density functional theory (DFT) studies suggest that the aryloxide acts as a base to form a Cu(II)-bound enolate, whereas the nitroolefin is activated by H-bonds to the imidazolium unit and the phenolic OH generated during the proton transfer. Detailed kinetic analyses (RPKA, VTNA) suggest that (a) the catalyst is stable during the catalytic reaction, (b) not inhibited by product and (c) the rate-limiting step is most likely the C-C bond formation in agreement with the DFT calculations of the catalytic cycle. The robust catalyst is readily synthesized and recyclable and could also be applied to a cascade cyclization.

The reaction of [W(N-2,6-iPr2C6H3)(CHCMe2Ph)(OTf)2(DME)] (DME = 1,2-dimethoxyethane, OTf = CF3SO3) with the N-heterocyclic carbene (NHC) 1,3-bis(2,4,6-trimethylphenyl)imidazolidin-2-ylidene (IMesH2) leads to DME activation followed by transmethylation and in due consequence to the formation of the N-heterocyclic olefin complex [W(N-2,6-iPr2C6H3)(CHCMe2Ph)(OTf)2(IMesH2CH2)] along with [W(N-2,6-iPr2C6H3)(CHCMe2Ph)(OTf)(IMesH2)(κ2-O(CH2)2OMe)], [1,3-bis(2,4,6-trimethylphenyl)-2-methylimidazolidinium+ (OTf−)] and [1,3-bis(2,4,6-trimethylphenyl)-2-H-imidazolidinium+ (OTf−)]. A reaction pathway is proposed and confirmed by the use of 13C-labelled compounds; structures of the products were verified by NMR and/or single-crystal X-ray analysis.

Six molybdenum imido alkylidene complexes bearing an N-chelating N-heterocyclic carbene (NHC), i.e., Mo(N-2,6-Me2-C6H3)(CHCMe2Ph)(1-(2-pyridyl)methylene-3-mesitylimidazol-2-ylidene)(OTf)2 (1), Mo(N-2,6-Me2-C6H3)(CHCMe2Ph)(1-(2-pyridyl)methylene-3-mesitylimidazol-2-ylidene)(OTf)(OC6F5) (3), Mo(N-2,6-Me2-C6H3)(CHCMe2Ph)(1-(2-pyridyl)methylene-3-mesitylimidazol-2-ylidene)(OTf)(OCMe3) (4), and their cationic counterparts [Mo(N-2,6-Me2-C6H3)(CHCMe2Ph)(1-(2-pyridyl)methylene-3-mesitylimidazol-2-ylidene)(OTf)]B(ArF)4 (2), [Mo(N-2,6-Me2-C6H3)(CHCMe2Ph)(1-(2-pyridyl)methylene-3-mesitylimidazol-2-ylidene)(OC6F5)]B(ArF)4 (5), and [Mo(N-2,6-Me2-C6H3)(CHCMe2Ph)(1-(2-pyridyl)methylene-3-mesitylimidazol-2-ylidene)(OCMe3)]B(ArF)4 (6), have been prepared. The influence of the alkoxide ligand on the loss of triflate in the hexacoordinated complexes 1, 3, and 4 resulting in the corresponding cationic complexes was studied. The 2-pyridyl-donor-functionalized NHC ligand renders the high oxidation state cationic molybdenum imi...

Macroalgae are potential feedstock for biorefineries. However, integration of macroalgae into biorefinery network requires new processing technologies that will lead to energy efficient and zero waste conversion of macroalgae biomass into food, chemicals and fuels. Here we report on the selective extraction of proteins from green macroalgae from Ulva genus by electroporation with energy efficient pulsed electric field (PEF) process. We show that application of 75 pulses with an average electric field strength of 2.964 ± 0.007 kV cm − 1 , and pulse duration 5.70 ± 0.30 μs, delivered at approximately 0.5 Hz, combined with hydraulic pressing of the treated samples for 5 min with force of 45 daN cm − 2 led to the total protein concentration of 59.13 ± 3.82 μg mL − 1 in the extracted juice. The final temperature of the extracted juice was 35.50 ± 2.02 °C. The energy consumption of the process is 251 ± 3 kWh kg − 1 of protein. We show that PEF process is selective and its extraction efficiency and damage are protein specific.

Pulsed electric field (PEF) treatment of microalgae has been demonstrated to exhibit processing advantages compared to conventional processing. Besides low specific energy requirements, PEF treatment can separate microalgae biomass into aqueous and oleaginous fractions. To minimize processing energy demand, the treatment of pre-concentrated microalgae suspensions is advantageous. For suspensions with a biomass density of approximately 80 g of dry weight per liter, microalgae precipitation at the electrodes of cross-linear treatment chambers was observed. This phenomenon is examined using the microalgae species Chlorella vulgaris and Auxenochlorella protothecoides. An interrelation between pH and zeta potential on the one hand and the amount of precipitated microalgae on the electrodes on the other hand is emerging. Impact of electric pulse parameters and pH was investigated and suggested that precipitation is caused by electrophoretic forces. The results indicate that shorter pulses can be used to reduce the unwanted precipitation. Industrial relevance The manuscript describes an undesirable effect occurring while performing pulsed electric field (PEF) treatment on microalgae. We have indeed observed that microalgae tend to precipitate on the surface of the treatment electrodes during PEF processing. This precipitation of microalgae results in the distortion of the flow through the treatment chamber and in the modification of the electric field distribution. At an industrial scale, this will affect the process efficiency and therefore increase processing costs. In the worst case, the affected electroporation reactors might be blocked and require additional maintenance, generating extra costs. We demonstrate that the precipitation is induced by the interaction between the electric field and the surface-charged algae. Driving parameters for the precipitation effect were identified and strategies to avoid it are proposed in the manuscript.

Tetrakis(dimethoxyphenyl)adamantane (TDA) readily forms crystalline inclusion complexes with reactive, toxic, or malodorous reagents, such as benzoyl chloride, acetyl chloride, cyclohexyl isocyanide, phosphorus trichloride, and trimethylsilyl chloride. The crystals are stable and largely free of the problematic properties of the free reagents. When exposed to solvents such as DMSO or MeOH, the reagents react, and a large portion of the TDA precipitates. The TDA-coated reagents may lead to a safer way of storing, handling, and delivering reagents, and ultimately to synthetic protocols that do not require fume hoods.

Substrates bearing both a β-ketoester moiety and a (het)aryl halide structure element were dimerized to 1-naphthols and related products in the presence of catalytic amounts of CuI in isopropanol. The reaction starts with an intermolecular C-arylation, which is followed by an intramolecular condensation. The final aromatization delivers the highly substituted products with yields up to 81%.

2-(1-Benzyl-1H-1,2,3-triazol-4-yl)-imidazolines (L1 and L2/L2′), -1,3-oxazoline (L3), -1,3-thiazoline (L4) and -tetrahydropyrimidine (L5) were prepared in one step from a 1,2,3-triazole-4-carboxamidinium tetraphenylborate and studied as novel ligands for copper(II) and nickel(II) ions. The solid-state structures of the following complexes were established: [Cu(L1)2](OTf)2, [CuL2L2′(OTf)2] · 2H2O, [[Cu(L4)2(H2O)2](OTf)2 · [Cu(L4)2(OTf)2], [Cu(L5)2(OTf)2], Cu(L3)2Cl2] · THF, [Ni(L1)2Cl2].

The streamlined catalytic access to enantiopure allylic amines as valuable precursors towards chiral β- and γ-aminoalcohols as well as α- and β-aminoacids is desirable for industrial purposes. In this article an enantioselective method is described that transforms achiral allylic alcohols and N-tosylisocyanate in a single step into highly enantioenriched N-tosyl protected allylic amines via an allylic carbamate intermediate. The latter is likely to undergo a cyclisation-induced [3,3]-rearrangement catalysed by a planar chiral pentaphenylferrocene palladacycle in cooperation with a tertiary amine base. The otherwise often indispensable activation of palladacycle catalysts by a silver salt is not required in the present case and there is also no need for an inert gas atmosphere. To further improve the synthetic value, the rearrangement was used to form dimethylaminosulfonyl-protected allylic amines, which can be deprotected under non-reductive conditions.

A transition metal-free, diastereospecific reaction between substituted (Z)-1,2-dibromo-3-phenyl-2-propenes and substituted catechols using Cs2CO3 as a base at 140 °C for 18 h delivers exclusively substituted (Z)-2-arylidene-2,3-dihydrobenzo[b][1,4]dioxines in yields up to 89%. Experiments as well as quantum chemical calculations support the assumption that the one pot transformation proceeds as an intermolecular O-allylation/intramolecular O-vinylation.

We present the in-depth determination of the magnetic properties and electronic structure of the luminescent and volatile dysprosium-based single molecule magnet [Dy2(bpm)(fod)6] (Hfod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione, bpm = 2,2-bipyrimidine)., We present the in-depth determination of the magnetic properties and electronic structure of the luminescent and volatile dysprosium-based single molecule magnet [Dy2(bpm)(fod)6] (Hfod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione, bpm = 2,2′-bipyrimidine). Ab initio calculations were used to obtain a global picture of the electronic structure and to predict possible single molecule magnet behaviour, confirmed by experiments. The orientation of the susceptibility tensor was determined by means of cantilever torque magnetometry. An experimental determination of the electronic structure of the lanthanide ion was obtained combining Luminescence, Far Infrared and Magnetic Circular Dichroism spectroscopies. Fitting these energies to the full single ion plus crystal field Hamiltonian allowed determination of the eigenstates and crystal field parameters of a lanthanide complex without symmetry idealization. We then discuss the impact of a stepwise symmetry idealization on the modelling of the experimental data. This result is particularly important in view of the misleading outcomes that are often obtained when the symmetry of lanthanide complexes is idealized.

Pulsed electric field (PEF) treatment was evaluated for phycocyanin and proteins extraction from Arthrospira platensis (Spirulina platensis). PEF extractions were performed using different specific energies (28, 56 and 122 J·ml−1 of suspension) and the results were compared to the extraction with bead milling. At highest PEF-treatment energies a damage of the cell morphology could be observed and the highest yields (up to 85.2 ± 5.7 mg·g−1 and 48.4 ± 4.4 g·100 g−1 of phycocyanins and proteins, respectively) could be obtained at 122 and 56 J·ml−1. The yields increased with incubation time after PEF-treatment. The antioxidant capacity of the extracts obtained after PEF-treatment was higher than of those obtained after bead milling. PEF treatment is a promising technology to obtain blue-green antioxidant extracts from A. platensis in an environmental friendly process.

International audience; In this work, the synthesis, X-ray crystal structure analysis, studies on meso-morphism and luminescence spectroscopy of 2,7-diphenyl-4,5-diazafluorenones carrying 2, 4 or 6 peripheral alkoxy side chains of different lengths in the mesogenic unit are reported. The latter was attached to starting 2,7-dibromo-4,5-diazafluoren-9-one via Suzuki cross coupling of the respective 2-(alkoxyphenyl)-tetramethyl-1,2,3-borolane. The liquid crystalline properties were found to depend on both the number of side chains and their lengths. Derivatives with two short alkoxy chains (C6-C8) in the periphery formed nematic (N) and smectic C (SmC) mesophases while for the higher homologues only SmC mesophases were observed. Compounds carrying six alkoxy side chains with a minimum length of C8 assembled into columnar hexagonal phases. Homologues with C14 and C16 chain length displayed additionally two columnar rectangular mesophases. Four peripheral alkoxy chains, however, led to the loss of mesomorphism. Crystal structure data of a series of rod-shaped diazafluorenones helped to rationalize their liquid crystalline self-assembly and to understand geometry and thermal stability. Temperature-dependent luminescence spectra of diazafluorenone with two C12 chains revealed aggregation-induced emission (AIE) depending on the supramolecular order of the bulk phase. These studies suggested that AIE requires a lower degree of aggregation as compared to mesophase formation.

We present the in-depth determination of the magnetic properties and electronic structure of the luminescent and volatile dysprosium-based single molecule magnet [Dy2(bpm)(fod)6] (Hfod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione, bpm = 2,2'-bipyrimidine). Ab initio calculations were used to obtain a global picture of the electronic structure and to predict possible single molecule magnet behaviour, confirmed by experiments. The orientation of the susceptibility tensor was determined by means of cantilever torque magnetometry. An experimental determination of the electronic structure of the lanthanide ion was obtained combining Luminescence, Far Infrared and Magnetic Circular Dichroism spectroscopies. Fitting these energies to the full single ion plus crystal field Hamiltonian allowed determination of the eigenstates and crystal field parameters of a lanthanide complex without symmetry idealization. We then discuss the impact of a stepwise symmetry idealization on the modelling of the experimental data. This result is particularly important in view of the misleading outcomes that are often obtained when the symmetry of lanthanide complexes is idealized. ispartof: CHEMICAL SCIENCE vol:10 issue:7 pages:2101-2110 ispartof: location:England status: published

International audience; A series of tetraguanidinium tetraphenylethene (TPE) arylsulfonates with different chain lengths was prepared via ionic self‐assembly of tetraguanidinium TPE chloride and the respective methyl arylsulfonates. Liquid crystalline properties were studied by differential scanning calorimetry, polarizing optical microscopy and X‐ray diffraction. Tetraguanidinium TPE arylsulfonates with chain lengths of C8–C12 displayed hexagonal columnar mesophases over a broad temperature range, while derivatives with longer chains showed oblique columnar phases. In solution all compounds displayed aggregation‐induced emission behaviour. Temperature‐dependent luminescence spectra of the bulk phase of the tetraguanidinium TPE arylsulfonate with C14 side chains revealed a strong luminescence both in the solid state and the oblique columnar mesophase. The emission behaviour was rationalized by a unique combination of restriction of intramolecular rotation of the TPE core, Coulomb interaction between the guanidinium cations and π–π interactions of the anionic arylsulfonate moieties.

Photoautotrophic microalgae based biorefinery concepts are currently not competitive compared to other established production systems. Therefore, innovative upstream processes need to be developed to increase the competitiveness of photoautotrophic microalgae biorefinery concepts. Abiotic sub-lethal stress induction via nanosecond pulsed electric field (nsPEF) treatment might be a viable process to increase the efficiency of photoautotrophic microalgae cultivation. In this work, an increased cell growth after nsPEF treatment was observable. Application of nsPEF to highly proliferating cells in a repetitive process resulted in a statistical significant increase in cell growth (p = 0.009). The effect was most pronounced after five days wherefore cellular structures and processes were analyzed to reveal a possible mechanism. Within this work, a protocol for increased cell proliferation with a possible mechanism was derived, which improves competitiveness of photoautotrophic microalgae biorefineries in the future. However, based on the derived mechanism, the results are also relevant for other microorganisms., Bioresource Technology, 271, ISSN:1873-2976, ISSN:0960-8524

Asymmetric 1,2-additions of cyanide yield enantioenriched cyanohydrins as versatile chiral building blocks. Next to HCN, volatile organic cyanide sources are usually used. Among them, cyanoformates are more attractive on technical scale than TMSCN for cost reasons, but catalytic productivity is usually lower. Here, the development of a new strategy for cyanations is described, in which this activity disadvantage is overcome. A Lewis acidic Al center cooperates with an aprotic onium moiety within a remarkably robust bifunctional Al-F-salen complex. This allowed for unprecedented turnover numbers of up to 104 . DFT studies suggest an unexpected unique trimolecular pathway in which the ammonium bound cyanide attacks the aldehyde, which itself is activated by the carbonyl group of the cyanoformate binding to the Al center. In addition, a novel practical carboxycyanation method was developed that makes use of KCN as the sole cyanide source. The use of a pyrocarbonate as carboxylating reagent provided the best results.

A concise enantioselective total synthesis of three sesquiterpenoid alkaloids—(−)-dendrobine, (−)-mubironine B, and (−)-dendroxine—is presented, which highlights the state-of-art catalytic methods, including enantioselective Diels–Alder cycloaddition, iron-catalyzed aerobic lactonization, copper-catalyzed cycloisomerization, and free-radical-initiated hydroazidation.

Cationic Fe complexes of the general type [(Ph3 P)2 Fe(CO)(NO)]X (X=BF4 , BArF4 ) catalyze the redox-neutral cycloisomerization of 1,6- and 1,7-enyneacetates to afford bicyclic cyclobutanes under mild conditions in good yields and diastereoselectivities.

Cembranoids constitute a large family of 14-membered oxygenated macrocyclic diterpenoids with potential as therapeutic agents. Selective late-stage oxidations of cembranoid scaffolds remain a challenge for chemical catalysts but can be accomplished by enzymes. Here, a new chemoenzymatic route to oxyfunctionalized 14-membered macrocycles including cembranoids is described. This route combines a metal-catalyzed ring-closing metathesis with a subsequent P450 BM3-catalyzed hydroxylation and delivers cembranoid-like analogues. Systematic substrate probing with a set of synthetic 14-membered macrocycles revealed that the regioselectivity of a P450 BM3-based biocatalyst increased with increasing ring rigidity as well as size and polarity of the exocyclic substituents. Enzyme regioselectivity could further be improved by first-sphere active site mutagenesis. The V78A/F87A variant catalyzed hydroxylation of cembranoid-ol (9S/R)-3 d with 90 % regioselectivity for C5 position. Extensive NMR analysis of Mosher esters and single crystal X-ray structure determination revealed a remarkable diastereoselectivity of this P450 BM3 mutant depending on substrate stereochemistry, which led exclusively to the syn-cembranoid-diols (5S,9S)-4 and (5R,9R)-4.

C20H17NO2S, triclinic, P1̅ (no. 2), a = 8.2737(5) Å, b = 16.6403(9) Å, c = 17.733(1) Å, α = 86.372(3)°, β = 86.317(4)°, γ = 78.607(3)°, V = 2385.2(2) Å3, Z = 6, R gt (F) = 0.0429, wR ref (F 2 ) = 0.1086, T = 100 K.

The novel dialkylzirconium complexes L′ZrR2, (R = CH3, Bn = benzyl, CH2SiMe3, L′ = Me2Si{η5-tetramethylcyclopentadienyl}{6-[2-(dimesitylboryl)phenyl]pyrid-2-ylamido}) were synthesized. Upon activation with 1 equiv. of [Ph3C]+[B(C6F5)4]−, both L′Zr(CH3)2 and L′Zr(Bn)2 are quantitatively converted in situ into [L′Zr(CH3)]+[B(C6F5)4]− and [L′Zr(Bn)]+[B(C6F5)4]− while only 28 mol% conversion is observed with L′Zr(CH2SiMe3)2. The aluminum-free cationic catalysts [L′Zr(CH3)]+[B(C6F5)4]−, [L′Zr(Bn)]+[B(C6F5)4]− and [L′Zr(CH2SiMe3)]+[B(C6F5)4]− initiate ring-opening metathesis polymerization (ROMP) of NBE to form predominantly cis-poly(NBE)ROMP. Upon activation with [Ph3C]+[B(C6F5)4]− and AliBu3, L′Zr(CH3)2, L′Zr(Bn)2 and L′Zr(CH2SiMe3)2 also exhibit moderate catalytic activity in the copolymerization of ethylene (E) with NBE. The resulting copolymers do not contain any ROMP-derived poly(NBE), which is in stark contrast to the complexes’ homopolymerization propensity for NBE. Upon activation with methylalumoxane (MAO), L′Zr(CH3)2 and L′Zr(Bn)2 produce pure vinyl-insertion polymerization-derived poly(NBE)-co-poly(E) while L′Zr(CH2SiMe3)2 allows for the synthesis of predominantly trans-poly(NBE)ROMP-co-poly(NBE)VIP-co-poly(E)-based copolymers via an α-H+ elimination/addition process. Our findings are discussed on the basis of the instability of the alkylidenes in the presence of E and the blocking effect of aluminum alkyls on ROMP via coordination to the pyridyl-moiety in the cationic complexes.

One pot synthesis of two novel hitherto unreported thiophenes was achieved by a facile and selective synthetic method. The crystal structures of the synthesized compounds were determined using an X-ray single crystal technique. The synthesized thiophenes were evaluated for their anti-cancer and antimicrobial activities. Molecular docking studies of the synthesized compounds were performed by (MOE). The predicted results from the molecular docking studies were in complete agreement with the experimental data for antimicrobial evaluation.

The use of a convenient protecting group for boronates allows a selective, catalyzed S(N)2' reaction to generate allylboronates which are applied for the synthesis of enantiomerically pure homoallylic alcohols. Depending on the configuration of both catalyst and the protecting group any of the four possible stereoisomers can be formed. The rationale behind the selective addition is supported by density functional theory calculations.

The Michael addition of enaminoesters to coumarins (1) does not lead to the formation of simple adducts3but to the rearranged 4-aryl-2-pyridone4a. Now,N-carbamoylation of the 6-amino-2-pyridone4awith alkyl isocyanates and further transformation of the corresponding novel ureido-2-pyridone derivatives6a–ginto chromeno[3,4-c]pyridines5d,gandO-acetyl derivatives7a–gare reported. All newly synthesized compounds were characterized by means of1H/13C NMR, MS, IR spectra and elemental analysis. The structure of the ureide6fand of theN-cyclohexyl-O-acetyl derivative7gwere additionally confirmed by crystal structure determinations. Acute toxicity after intraperitoneal administration, blood clotting time, analgesic activity and the effects on the hexobarbital sleeping time were tested on laboratory animals (compounds4a,6a,6c,6dand6g).

The electronic structure of a novel lanthanide-based single-ion magnet, {C(NH2)3}5[Er(CO3)4]·11H2O, was comprehensively studied by means of a large number of different spectroscopic techniques, including far-infrared, optical, and magnetic resonance spectroscopies. A thorough analysis, based on crystal field theory, allowed an unambiguous determination of all relevant free ion and crystal field parameters. We show that inclusion of methods sensitive to the nature of the lowest-energy states is essential to arrive at a correct description of the states that are most relevant for the static and dynamic magnetic properties. The spectroscopic investigations also allowed for a full understanding of the magnetic relaxation processes occurring in this system. Thus, the importance of spectroscopic studies for the improvement of single-molecule magnets is underlined.

The synthesis and single-crystal X-ray structures of the novel molybdenum imido alkylidene N-heterocyclic carbene complexes [Mo(N-2,6-Me2C6H3)(IMesH2)(CHCMe2Ph)(OTf)2] (3), [Mo(N-2,6-Me2C6H3)(IMes)(CHCMe2Ph)(OTf)2] (4), [Mo(N-2,6-Me2C6H3)(IMesH2)(CHCMe2Ph)(OTf){OCH(CF3)2}] (5), [Mo(N-2,6-Me2C6H3)(CH3CN)(IMesH2)(CHCMe2Ph)(OTf)](+)BArF(-) (6), [Mo(N-2,6-Cl2C6H3)(IMesH2)(CHCMe3)(OTf)2] (7) and [Mo(N-2,6-Cl2C6H3)(IMes)(CHCMe3)(OTf)2] (8) are reported (IMesH2=1,3-dimesitylimidazolidin-2-ylidene, IMes=1,3-dimesitylimidazolin-2-ylidene, BArF(-)=tetrakis-[3,5-bis(trifluoromethyl)phenyl] borate, OTf=CF3SO3(-)). Also, silica-immobilized versions I1 and I2 were prepared. Catalysts 3-8, I1 and I2 were used in homo-, cross-, and ring-closing metathesis (RCM) reactions and in the cyclopolymerization of α,ω-diynes. In the RCM of α,ω-dienes, in the homometathesis of 1-alkenes, and in the ethenolysis of cyclooctene, turnover numbers (TONs) up to 100,000, 210,000 and 30,000, respectively, were achieved. With I1 and I2, virtually Mo-free products were obtained (

The regio- and stereoselective cyclopolymerization of a series of 1,6-heptadiynes and 1,7-octadiynes, i.e., of 4,4-bis(ethoxycarbonyl)-1,7-heptadiyne (M1), 4-ethoxycarbonyl-4-(1R,2S,5R)-(−)-menthyloxycarbonyl-1,6-heptadiyne (M2), (R,S)-4,5-bis((1R,2S,5R)-(−)-menthyloxymethylcarboxymethyl)-1,7-octadiyne (M3), and (S,S/R,R)-4,5-bis((1R,2S,5R)-(−)-menthyloxymethylcarboxymethyl)-1,7-octadiyne (M4), by the action of the molybdenum–imidoalkylidene N-heterocyclic carbene (NHC) complexes (Mo(N-2,6-Me2C6H3)(CHCMe2Ph)(OTf)2(IMesH2) (I1), Mo(N-2,6-Me2C6H3)(CHCMe3)(OTf)2(IMesH2) (I2), (Mo(N-2,6-Me2-C6H3)(CHCMe2Ph)(OTf)(OCH(CF3)2)(IMesH2) (I3), Mo(N-2,6-Cl2C6H3)(CHCMe3)(OTf)2(IMes) (I4, IMesH2 = 1,3-dimesitylimidazolidin-2-ylidene, IMes = 1,3-dimesitylimidazolin-2-ylidene) and by the molybdenum–imidoalkylidene monoaryloxide monopyrrolide (MAP) complexes Mo(N-2,6-iPr2-C6H3)(CHCMe2Ph)(2,5-Me2-pyrrolide)(O-2,6-Me2-C6H3) (MAP1), Mo(N-2,6-iPr2-C6H3)(CHCMe2Ph)(2,5-Me2-pyrrolide)(O-2,6-Mes2-C6H3) (MAP2), and Mo(N-2-tBu-C6H4)...