ChemInform Abstract: Copper‐Catalyzed Difluoromethylation of Aryl Iodides with (Difluoromethyl)zinc Reagent.

Assessment of algal biofuel resource potential in the United States with consideration of regional water stress

The combination of difluoroiodomethane and zinc dust or diethylzinc can readily lead to (difluoromethyl)zinc reagents. Therefore, the first copper-catalyzed difluoromethylation of aryl iodides with the zinc reagents is accomplished to afford the difluoromethylated arenes. The reaction proceeds efficiently through the ligand/activator-free operation without addition of ligands for copper catalyst (e.g., phen and bpy) and activators for zinc reagent (e.g., KF, CsF, and NaO-t-Bu). Moreover, transmetalation of the CF2H group from zinc reagent to copper catalyst proceeds even at room temperature to form the cuprate [Cu(CF2H)2](-).

The palladium-catalyzed Negishi cross-coupling reaction of aryl iodides and bromides with (difluoromethyl)zinc reagent bearing a diamine such as TMEDA is achieved to provide the difluoromethylated aromatic compounds in good to excellent yields. The advantages of (difluoromethyl)zinc reagent are that (1) the derivatives, which possess different stability and reactivity, can be readily prepared via ligand screening and (2) transmetalation of a difluoromethyl group from the zinc reagent to palladium catalyst efficiently proceeds without an activator.

Synthetic applications of ethyl 3-bromodifluoromethyl-3-benzyloxy-acrylate as a gem-difluorination building-block: Its reactions with aldehyde and epoxide

A novel Zn-mediated preparation of propiolonitriles using electrophilic cyanation of alkynyl bromides with N-cyano-N-phenyl-p-methylbenzenesulfonamide (NCTS) has been achieved here. The zinc dust was firstly used to activate the C(sp)–Br bond in the presence of tetrabutylammonium iodide (TBAI) to form an alkynyl zinc reagent in situ, which would undergo a nucleophilic addition with NCTS at the cyano group to afford an imine. Finally the propiolonitrile product was obtained after the elimination of the zinc complex. According to this new protocol, various phenylpropiolonitriles have been prepared from alkynyl bromides in moderate to excellent yields (51–95%), and could also be generated from the combination of inactive alkynyl chlorides with tetrabutylammonium bromide (TBAB) in lower yields (23–70%).

During start-up of the CERN AA, many hours of machine experiments went into the study and optimization of antiproton yields. Those involved in the commissioning programme experienced the difficulty of tuning a new machine to accept a low-intensity full-aperture beam. The antiproton yield could only be obtained by integrating a slow Schottky scan of the beam on the injection orbit, normalized with respect to primary beam intensity by a charge transformer just in front of the production target. A precise yield measurement took about five minutes. At high yields this method permitted measurements to within a few percent. The slowness of the multi-parameter yield optimization, starting from low yields where the measurement errors were often as large as the gains to be made, cannot be over emphasized. In the Tevatron I Debuncher the antiproton yields should be substantially higher than at the AA and, given a Schottky pick-up of sufficient sensitivity, the situation looks more promising. At the AA we have resolved some of our difficulties by improving the charge transformer signal, speeding up the Schottky scan and adding instrumentation to use the signals from pions, muons and electrons injected along with the antiprotons. Low yields, e.g. at reduced aperture,more » are now measured using beam scrapers in conjunction with counters calibrated against the Schottky pick-up at high intensities. The latter is itself calibrated by the circulating beam current transformer at even higher intenSities, usually with protons in reverse polarity mode. Based on the AA experience we outline the techniques that could be used for the following measurements and procedures at the Debuncher: (1) antiproton yield (number of antiprotons circulating in the Debuncher per incident proton) versus the machine apertures 6X, 6y, and 6p, (2) yield versus phase space coordinates downstream from the production target, (3) use of other secondary particle fluxes, (4) optimization of full-aperture yield at the start of and during antiproton accumulation.« less

Ethyl 3-bromo-3, 3-difluoropropionate (1) was prepared in an overall yield of 75% from the radical addition of dibromodifluoromethane to ethyl vinyl ether under Na2S2O4 initiation, followed by oxidation of the acetal with Caro acid. The treatment of 1 with active zinc dust in anhydrous DMF at room temperature produced the zinc reagent ZnBrCF2CH2CO2C2H5 (2). The cross coupling of the zinc reagent 2 with aryl (alkenyl) halides (R−X) in DMF using Pd(0)−Cu(I) as cocatalyst stereoselectively provided the β-fluoro-α,β-unsaturated esters (RCFCHCO2C2H5 4) directly and in moderate yields. An E/Z ratio ranging from 3:2 to 1:0 was observed. This is the first example that Cu(I) can improve the selectivity of the cross-coupling reaction. Mechanistic studies revealed that zinc reagent 2 underwent stereoselective elimination to produce (Z)-1-fluoro-2-(ethoxycarbonyl)ethenylzinc reagent 6, and then the cross-coupling of 6 with aryl(alkenyl) halides under palladium(0) catalysis afforded the β-fluoro-α,β-unsaturated esters 4.

Catalytic asymmetric cross-coupling

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Pincer thioamide Pd(II) complex 2 was prepared, and its reaction with cyclohexylzinc chloride yielded novel pincer thioimide Pd(II) complex 3 besides Pd(0) species. The structures of complexes 2 and 3 were confirmed by X-ray analysis. Both complexes are efficient catalysts for Negishi couplings involving primary and secondary alkyl zinc reagents bearing beta-hydrogen atoms. At a concentration of 0.1-0.5 mol % both catalysts readily promoted reactions at room temperature or even at 0 degrees C. The operational simplicity of these processes, in conjunction with the easy accessibility of both catalysts and substrates, promises synthetic utility of this new methodology. An experiment on a scale of 19.35 g carried out at very low catalyst loading of 2 (turnover number: 6,100,000) highlighted the potential application of the catalytic system. Monoalkyl and dialkyl zinc reagents displayed different reactivities and selectivities in reactions with aryl iodides catalyzed by complexes 2 or 3, and isomerization in reactions involving acyclic secondary alkyl zinc derivatives was suppressed by using appropriate amounts of dialkyl zinc reagents. Based on preliminary kinetic profiles and reaction evidence, three possible pathways are proposed for the reactions involving acyclic secondary alkyl zinc reagents to rationalize the difference between mono-alkyl and dialkyl zinc derivatives.

A catalytic system consisting of InCl3 (3 mol %) and LiCl (30 mol %) allows a convenient preparation of polyfunctional arylzinc halides via the insertion of zinc powder to various aryl iodides in THF at 50 °C in up to 95 % yield. The use of a THF/DMPU (1:1) mixture shortens the reaction rates and allows the preparation of keto-substituted arylzinc reagents. In the presence of In(acac)3 (3 mol %) and LiCl (150 mol %), the zinc insertion to various aryl and heteroaryl bromides proceeds smoothly (50 °C, 2-18 h). Alkyl bromides are also converted to the corresponding zinc reagents in the presence of In(acac)3 (10 mol %) and LiCl (150 mol %) in 70-80 % yield.

An interdisciplinary systems approach was used to explore the potential of fall, fresh-market broccoli as a new enterprise for eastern Virginia. Thirteen cultivars were evaluated in three plantings. Crop value was estimated at each harvest based on weekly market prices. The market window was open from mid-October until late November, with production of 160 cartons/ha, each at 11 kg. However, production of 120 cartons/ha narrowed the window to 2 weeks. Yield of some cultivars exceeded 160 cartons/ha in the first planting; yield of others was below the target production in the second planting. Low yield and low prices during most of the harvest period for the second planting suggests that the optimum harvest season ends in mid- to late November. Problems with poor plant establishment must be addressed before growers can fully capitalize on potential of broccoli as a new enterprise.

The C-N coupling reaction demonstrates broad application in the fabrication of a wide range of high value-added organonitrogen molecules including fertilizers (e.g., urea), chemical feedstocks (e.g., amines, amides), and biomolecules (e.g., amino acids). The electrocatalytic C-N coupling pathways from waste resources like CO2, NO3-, or NO2- under mild conditions offer sustainable alternatives to the energy-intensive thermochemical processes. However, the complex multistep reaction routes and competing side reactions lead to significant challenges regarding low yield and poor selectivity toward large-scale practical production of target molecules. Among diverse catalyst systems that have been developed for electrochemical C-N coupling reactions, the atomically dispersed catalysts with well-defined active sites provide an ideal model platform for fundamental mechanism elucidation. More importantly, the intersite synergy between the active sites permits the enhanced reaction efficiency and selectivity toward target products. In this Review, we systematically assess the dominant reaction pathways of electrocatalytic C-N coupling reactions toward various products including urea, amines, amides, amino acids, and oximes. To guide the rational design of atomically dispersed catalysts, we identify four key stages in the overall reaction process and critically discuss the corresponding catalyst design principles, namely, retaining NOx/COx reactants on the catalyst surface, regulating the evolution pathway of N-/C- intermediates, promoting C-N coupling, and facilitating final hydrogenation steps. In addition, the advanced and effective theoretical simulation and characterization technologies are discussed. Finally, a series of remaining challenges and valuable future prospects are presented to advance rational catalyst design toward selective electrocatalytic synthesis of organonitrogen molecules.

Research progress of catalysts of the aldol condensation reaction of biomass based compounds is summarized for the synthesis of liquid fuel precursors and chemicals. In summary, an acidic catalyst, alkaline catalyst, acid–base amphoteric catalyst, ionic liquid and other catalysts can catalyze the aldol condensation reaction. The aldol condensation reaction catalyzed by an acid catalyst has the problems of low conversion and low yield. The basic catalyst catalyzes the aldol condensation reaction with high conversion and yield, but the existence of liquid alkali is difficult to separate from the product. The reaction temperature needed for oxide and hydrotalcite alkali is relatively high. The basic resin has good catalytic activity and at a low reaction temperature, and is easy to separate from the target product. Acid–base amphoteric catalysts have received extensive attention from researchers for their excellent activity and selectivity. Ionic liquid is a new type of material, which can also be used for the aldol condensation reaction. In the future application of aldol condensation, the development of strong alkaline resin is a good research direction.

Ethanol production by fermentation results in obtaining, in addition to the main product, ethyl alcohol, by-products and secondary products, which include carbon dioxide, fusel oil, and ester–aldehyde cut. Fusel oil, despite its low yield and the large volume of ethanol production, accumulates at distilleries, which ultimately raises the question of its disposal or the rational use of this by-product. Fusel oil, being a complex mixture, can serve as a source of technical alcohols used in various sectors of the economy, including the food industry, pharmaceuticals, organic synthesis, perfume, and cosmetics industries, as well as the production of paints and varnishes. However, the complexity of using fusel oil lies in its difficult separation. The reason for this is the presence of water, which forms low-boiling azeotropes with aliphatic alcohols. Our study aimed to develop a process flow diagram (PFD) that allows individual components from fusel oil to be obtained without extraneous separating agents (not inherent in fusel oil). This condition is necessary to obtain products labeled as natural for further use in the food, perfume, cosmetic, and pharmaceutical industries. The distinctive feature of this work is that the target product is not only isoamyl alcohol but also all other alcohols present in the composition of fusel oil. To achieve this goal and create a mathematical model, the Aspen Plus V14 application, the Non-Random Two Liquid (NRTL) thermodynamic model, and the Vap-Liq/Liq-Liq phase equilibrium were used. Fusel oil separation was modeled using a continuous separation PFD to obtain ethanol, water, isoamyl alcohol, and raw propanol and butanol cuts. The Sorel and Barbet distillation technique was used to isolate ethanol. The isolation of isopropanol and 1-propanol, as well as isobutanol and 1-butanol, was modeled using the batch distillation method. The isolation of fusel oil components was based on their thermodynamic properties and the selection of appropriate techniques for their separation, such as extraction, distillation, pressure swing distillation, and decantation. The simulation of fusel oil separation PFD showed the possibility of obtaining the components of a complex mixture without separating agents, as discussed earlier. Ethanol corresponds to the quality of rectified ethyl alcohol, and 1-butanol and isoamyl alcohols to anhydrous alcohols, whereas isopropanol (which contains an admixture of ethanol), 1-propanol, and isobutanol are obtained as aqueous solutions of different concentrations of alcohols. However, due to a distillation boundary in the raw propanol and butanol cuts, these mixtures cannot be separated completely, which leads to the production of intermediate fractions. To eliminate intermediate fractions and obtain anhydrous isopropanol, 1-propanol, and isobutanol in the future, it is necessary to solve the dehydration problem of either fusel oil or the propanol–butanol mixture.