scholarly journals Late-stage C–H thiolation via sulfonium salts using β-sulfinylesters as the versatile sulfur source

2021 ◽  
Author(s):  
Yanhui Chen ◽  
Si Wen ◽  
Qingyu Tian ◽  
Yuqing Zhang ◽  
Guolin Cheng
Keyword(s):  
Michael Reaction ◽  
Bond Cleavage ◽  
Sulfur Source ◽  
Reaction Conditions ◽  
Sulfonium Salts ◽  
Drug Molecules ◽  
Organic Sulfides ◽  
Wide Range ◽  
Successful Capture

Abstract Organic sulfides form the core scaffold of a wide range of pharmaceuticals, natural products, and materials, and serve as key intermediates in synthesis. Prior methods to organic sulfides require the use of transition metal (TM) catalysts, prefunctionalized or chelating group-containing substrates, and elevated reaction temperatures. A general TM-free C–H thiolation protocol using readily accessible sulfur source is highly desirable. Herein, we disclose a direct C(sp)–, C(sp2)–, and C(sp3)–H thiolation reaction using β-sulfinylesters as the versatile sulfur source. The key step of this protocol is chemoselective C–S bond cleavage of the sulfonium salts that is in situ formed from the corresponding (hetero)arenes, alkenes, alkynes, and 1,3-dicarboxyl compounds with β-sulfinylesters. The successful capture of acrylate byproduct supports a retro-Michael reaction mechanism. This method is expected to be used widely because of several advantageous aspects including TM-free, mild reaction conditions, and broad substrate scope including drug molecules.

Molybdenum-Mediated One-Pot Synthesis of Pyrazoles from Isoxazoles

Synthesis ◽  
2019 ◽  
Vol 51 (20) ◽  
pp. 3796-3804 ◽  
Author(s):  
Marine Rey ◽  
Stéphane Beaumont
Keyword(s):  
Bond Cleavage ◽  
Direct Synthesis ◽  
Molybdenum Complex ◽  
One Pot ◽  
One Pot Synthesis ◽  
Wide Range ◽  
Hydrolysis Of ◽  
Substituted Pyrazoles

A one-pot approach for the direct synthesis of substituted pyrazoles from isoxazoles is reported. The process involves isoxazole N–O bond cleavage mediated by a molybdenum complex, in situ hydrolysis of the resulting β-amino enone to the corresponding 1,3-diketone, followed by pyrazole formation in the presence of hydrazine or substituted hydrazine. Good to excellent yields and regioselectivities are obtained with nonsymmetric isoxazoles. By using readily available starting materials, a wide range of substituted pyrazoles may be synthesized by this method.

Cu-Catalyzed Allylation of Amines with Cyclopropyldiphenylsulfonium Trifluoromethanesulfonate

Synthesis ◽  
2022 ◽  
Author(s):  
Yu Ma ◽  
Ze-Yu Tian ◽  
Shuang-Yang Zheng ◽  
Cheng-Pan Zhang
Keyword(s):  
Aromatic Amines ◽  
Functional Group ◽  
Secondary Amines ◽  
Reaction Conditions ◽  
Drug Molecules ◽  
Wide Range ◽  
Catalyzed Reactions ◽  
Cyclic Compounds

Cyclopropyldiphenylsulfonium salt is a famous ylide precursor that was previously extensively employed in the preparation of cyclic compounds and has been successfully utilized as an efficient allylation reagent in this work. The Cu-catalyzed reactions of cyclopropyldiphenylsulfonium trifluoromethanesulfonate with amines in the presence of an appropriate ligand provided the N-allylated products in good yields. Aliphatic/aromatic amines and primary/secondary amines were all mildly converted under the reaction conditions. This protocol was also applicable to N-functionalization of drug molecules, supplying the corresponding N-allylated compounds in satisfactory yields. The reaction showed good functional group tolerance, a wide range of substrates, and excellent chemoselectivity, which offered an interesting method for the synthesis of N-allyl amines.

scholarly journals Preparation, Characterization, and Optimization of an In Vitro C30 Carotenoid Pathway

2005 ◽  
Vol 71 (11) ◽  
pp. 6578-6583 ◽  
Author(s):  
Bosung Ku ◽  
Jae-Cheol Jeong ◽  
Benjamin N. Mijts ◽  
Claudia Schmidt-Dannert ◽  
Jonathan S. Dordick
Keyword(s):  
Phase System ◽  
Reaction Conditions ◽  
Two Phase ◽  
Gene Encoding ◽  
In Situ Extraction ◽  
Steady State Kinetics ◽  
Wide Range ◽  
Carotenoid Synthesis

ABSTRACT The ispA gene encoding farnesyl pyrophosphate (FPP) synthase from Escherichia coli and the crtM gene encoding 4,4′-diapophytoene (DAP) synthase from Staphylococcus aureus were overexpressed and purified for use in vitro. Steady-state kinetics for FPP synthase and DAP synthase, individually and in sequence, were determined under optimized reaction conditions. For the two-step reaction, the DAP product was unstable in aqueous buffer; however, in situ extraction using an aqueous-organic two-phase system resulted in a 100% conversion of isopentenyl pyrophosphate and dimethylallyl pyrophosphate into DAP. This aqueous-organic two-phase system is the first demonstration of an in vitro carotenoid synthesis pathway performed with in situ extraction, which enables quantitative conversions. This approach, if extended to a wide range of isoprenoid-based pathways, could lead to the synthesis of novel carotenoids and their derivatives.

scholarly journals Turning a Methanation Catalyst into a Methanol Producer: In-Co Catalysts for the Direct Hydrogenation of CO2 to Methanol

2018 ◽  
Author(s):  
Anastasiya Bavykina ◽  
Irina Yarulina ◽  
Lieven Gevers ◽  
Mohamed Nejib Hedhili ◽  
Xiaohe Miao ◽  
...  
Keyword(s):  
Fossil Fuels ◽  
Close Contact ◽  
Active Phase ◽  
Reaction Conditions ◽  
Hydrogenation Of Co2 ◽  
Co Catalysts ◽  
Wide Range ◽  
Direct Hydrogenation ◽  
Co Precipitation

<div> <div> <div> <p>The direct hydrogenation of CO2 to methanol using green hydrogen is regarded as a potential technology to reduce greenhouse gas emissions and the dependence on fossil fuels. For this technology to become feasible, highly selective and productive catalysts that can operate under a wide range of reaction conditions near thermodynamic conversion are required. Here, we demonstrate that indium in close contact with cobalt catalyses the formation of methanol from CO2 with high selectivity (>80%) and productivity (0.86 gCH3OH.gcatalyst-1.h-1) at conversion levels close to thermodynamic equilibrium, even at temperatures as high as 300 °C and at moderate pressures (50 bar). The studied In@Co system, obtained via co- precipitation, undergoes in situ transformation under the reaction conditions to form the active phase. Extensive characterization demonstrates that the active catalyst is composed of a mixed metal carbide (Co3InC0.75), indium oxide (In2O3) and metallic Co. </p> </div> </div> </div>

scholarly journals Organozinc Pivalates for Cobalt-Catalyzed Difluoroalkylarylation of Alkenes and Mechanistic Insights

2021 ◽  
Author(s):  
Xinyi Cheng ◽  
Xingchen Liu ◽  
Shengchun Wang ◽  
Ying Hu ◽  
Bingjing Hu ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Functional Groups ◽  
Halogen Atom ◽  
Cobalt Catalyst ◽  
Bond Formation ◽  
Single Electron Transfer ◽  
Mechanistic Studies ◽  
Reaction Conditions ◽  
Wide Range

Abstract A set of cobalt-catalyzed regioselective difluoroalkylarylation of both activated and unactivated alkenes with bench-stable solid arylzinc pivalates and difluoroalkyl bromides through a cascade Csp3‒Csp3/Csp3‒Csp2 bond formation has been developed under mild reaction conditions. Indeed, a wide range of functional groups on difluoroalkyl bromides, olefins, 1,3-dienes as well as (hetero)arylzinc pivalates are well tolerated by the cobalt-catalyst, thus furnishing three-component coupling products in good yields and with high regio- and diastereoselectivity. Kinetic experiments comparing arylzinc pivalates and conventional arylzinc halides highlight the unique reactivity of these new organozinc pivalates. Detailed mechanistic studies strongly support that the reaction involves direct halogen atom abstraction via single electron transfer to difluoroalkyl bromides from the in situ formed cobalt(I) species, thus realizing a Co(I)/Co(II)/Co(III) catalytic cycle.

Two new high-nuclearity copper(II) chloride oligomers with herringbone stacking patterns synthesized by in situ templation

2006 ◽  
Vol 84 (2) ◽  
pp. 140-145 ◽  
Author(s):  
Zhiyong Fu ◽  
Tristram Chivers
Keyword(s):  
Copper Chloride ◽  
Bond Cleavage ◽  
Chloride Salt ◽  
Two Dimensional ◽  
Reaction Conditions ◽  
Chloride Ligand ◽  
Chain Lengths ◽  
Copper Halides ◽  
Stacking Patterns

The use of trichloroiminophosphoranes Cl3P=NR to control the concurrent release of the templating cation [RNH3]+ and chloride ligand via in situ P—N and P—Cl bond cleavage produced two new copper(II) chloride oligomers. The nature of the organic substituent R was a factor in determining the chain lengths. For n-propyltrichloroiminophosphorane, the hexanuclear cluster [n-PrNH3]2[Cu6Cl14] (1) was obtained, while p-tolyltrichloroiminophosphorane generated the tetranuclear copper chloride salt [4-CH3C6H4NH3][2-Cl-4-CH3C6H3NH3][Cu4Cl10] (2). In both structures a two-dimensional framework displaying a herringbone arrangement is created by Cu—Cl secondary bonding interactions. The direct addition of the [n-PrNH3]+ cation to a CuCl2·2H2O solution under the same reaction conditions produced [n-PrNH3]2[CuCl4]. Key words: copper halides, templation, oligomers, two-dimensional frameworks.

scholarly journals Turning a Methanation Catalyst into a Methanol Producer: In-Co Catalysts for the Direct Hydrogenation of CO2 to Methanol

2018 ◽  
Author(s):  
Anastasiya Bavykina ◽  
Irina Yarulina ◽  
Lieven Gevers ◽  
Mohamed Nejib Hedhili ◽  
Xiaohe Miao ◽  
...  
Keyword(s):  
Fossil Fuels ◽  
Close Contact ◽  
Active Phase ◽  
Reaction Conditions ◽  
Hydrogenation Of Co2 ◽  
Co Catalysts ◽  
Wide Range ◽  
Direct Hydrogenation ◽  
Co Precipitation

<div> <div> <div> <p>The direct hydrogenation of CO2 to methanol using green hydrogen is regarded as a potential technology to reduce greenhouse gas emissions and the dependence on fossil fuels. For this technology to become feasible, highly selective and productive catalysts that can operate under a wide range of reaction conditions near thermodynamic conversion are required. Here, we demonstrate that indium in close contact with cobalt catalyses the formation of methanol from CO2 with high selectivity (>80%) and productivity (0.86 gCH3OH.gcatalyst-1.h-1) at conversion levels close to thermodynamic equilibrium, even at temperatures as high as 300 °C and at moderate pressures (50 bar). The studied In@Co system, obtained via co- precipitation, undergoes in situ transformation under the reaction conditions to form the active phase. Extensive characterization demonstrates that the active catalyst is composed of a mixed metal carbide (Co3InC0.75), indium oxide (In2O3) and metallic Co. </p> </div> </div> </div>

scholarly journals Organozinc pivalates for cobalt-catalyzed difluoroalkylarylation of alkenes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xinyi Cheng ◽  
Xingchen Liu ◽  
Shengchun Wang ◽  
Ying Hu ◽  
Binjing Hu ◽  
...  
Keyword(s):  
Cobalt Catalyst ◽  
Bond Formation ◽  
Vital Role ◽  
Transition Metal Catalysis ◽  
Single Electron Transfer ◽  
Mechanistic Studies ◽  
Reaction Conditions ◽  
Metal Catalysis ◽  
Wide Range

AbstractInstallation of fluorine into pharmaceutically relevant molecules plays a vital role in their properties of biology or medicinal chemistry. Direct difunctionalization of alkenes and 1,3-dienes to achieve fluorinated compounds through transition-metal catalysis is challenging, due to the facile β-H elimination from the Csp3‒[M] intermediate. Here we report a cobalt-catalyzed regioselective difluoroalkylarylation of both activated and unactivated alkenes with solid arylzinc pivalates and difluoroalkyl bromides through a cascade Csp3‒Csp3/Csp3‒Csp2 bond formation under mild reaction conditions. Indeed, a wide range of functional groups on difluoroalkyl bromides, olefins, 1,3-dienes as well as (hetero)arylzinc pivalates are well tolerated by the cobalt-catalyst, thus furnishing three-component coupling products in good yields and with high regio- and diastereoselectivity. Kinetic experiments comparing arylzinc pivalates and conventional arylzinc halides highlight the unique reactivity of these organozinc pivalates. Mechanistic studies strongly support that the reaction involves direct halogen atom abstraction via single electron transfer to difluoroalkyl bromides from the in situ formed cobalt(I) species, thus realizing a Co(I)/Co(II)/Co(III) catalytic cycle.

In-situ electrical-resistivity measurements in the high-voltage electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 68-69
Author(s):  
W. E. King
Keyword(s):  
Electrical Resistivity ◽  
Electron Microscope ◽  
High Voltage ◽  
Resistivity Measurements ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Wide Range ◽  
Helium Gas

A side-entry type, helium-temperature specimen stage that has the capability of in-situ electrical-resistivity measurements has been designed and developed for use in the AEI-EM7 1200-kV electron microscope at Argonne National Laboratory. The electrical-resistivity measurements complement the high-voltage electron microscope (HVEM) to yield a unique opportunity to investigate defect production in metals by electron irradiation over a wide range of defect concentrations.A flow cryostat that uses helium gas as a coolant is employed to attain and maintain any specified temperature between 10 and 300 K. The helium gas coolant eliminates the vibrations that arise from boiling liquid helium and the temperature instabilities due to alternating heat-transfer mechanisms in the two-phase temperature regime (4.215 K). Figure 1 shows a schematic view of the liquid/gaseous helium transfer system. A liquid-gas mixture can be used for fast cooldown. The cold tip of the transfer tube is inserted coincident with the tilt axis of the specimen stage, and the end of the coolant flow tube is positioned without contact within the heat exchanger of the copper specimen block (Fig. 2).

Site specific agricultural soil management with the use of new technologies

2013 ◽  
Vol 16 (1) ◽  
pp. 59-67
Keyword(s):  
New Technologies ◽  
Digital Interface ◽  
Appropriate Treatment ◽  
Wide Range ◽  
Soil Variation ◽  
Soil Information ◽  
Remote Sensing Techniques ◽  
Agricultural Areas

<p>The Soil Science Institute of Thessaloniki produces new digitized Soil Maps that provide a useful electronic database for the spatial representation of the soil variation within a region, based on in situ soil sampling, laboratory analyses, GIS techniques and plant nutrition mathematical models, coupled with the local land cadastre. The novelty of these studies is that local agronomists have immediate access to a wide range of soil information by clicking on a field parcel shown in this digital interface and, therefore, can suggest an appropriate treatment (e.g. liming, manure incorporation, desalination, application of proper type and quantity of fertilizer) depending on the field conditions and cultivated crops. A specific case study is presented in the current work with regards to the construction of the digitized Soil Map of the regional unit of Kastoria. The potential of this map can easily be realized by the fact that the mapping of the physicochemical properties of the soils in this region provided delineation zones for differential fertilization management. An experiment was also conducted using remote sensing techniques for the enhancement of the fertilization advisory software database, which is a component of the digitized map, and the optimization of nitrogen management in agricultural areas.</p>

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