Study of multicomponent synthesis of 7-alkyl or aryl-6H,7H-benzo[f]chromeno[4,3-b] chromen-6-ones involving N,N-disulfopiperidiniumbisulfate [DSPP][HSO4] as efficient recyclable homogeneous Brönsted acidic catalyst.

Herein, a new type of pyranocoumarin derivatives 7-alkyl or aryl-6H,7H-benzo[f]chromeno[4,3-b] chromen-6-ones (2a-h) was developed via three component reaction of 4-hydroxy coumarin, ß-naphthol and aliphatic/aryl aldehydes using 25 mol% of N,N-disulfopiperidinium bisulfate [DSPP][HSO4] as homogeneous recyclable Brönsted acidic ionic liquid catalyst in EtOAc under reflux to produce excellent yields (89-97%) of the products within 2-4 h reaction. In neat condition, the same reaction required 4.5 h to produce 90% yield of model product (2d) at 100 ℃, which took only 2.5 h to yield 97% of the same product in EtOAc under reflux temperature.

Ethylene/Styrene Copolymerization by (Me3SiC5H4)TiCl2(O-2,6-iPr2-4-RC6H2) (R = H, SiEt3)-MAO Catalysts: Effect of SiMe3 Group on Cp for Efficient Styrene Incorporation.

The synthesis and structural analysis of (Me3SiC5H4)TiCl2(OAr) [OAr = O-2,6-iPr2-4-RC6H2; R = H, SiEt3] revealed that it exhibits higher catalytic activities than (tBuC5H4)TiCl2(OAr), Cp*TiCl2(OAr), with efficient comonomer incorporation in ethylene/styrene copolymerization in the presence of a methylaluminoxane (MAO) cocatalyst. The catalytic activity in the copolymerization increased upon increasing the charged styrene concentration along with the increase in the styrene content in the copolymers, whereas the activities of other catalysts showed the opposite trend. (Me3SiC5H4)TiCl2(O-2,6-iPr2C6H3) displayed the most suitable catalyst performance in terms of its activity and styrene incorporation, affording amorphous copolymers with styrene contents higher than 50 mol% (up to 63.6 mol%) and with random styrene incorporation confirmed by 13C-NMR spectra.

Catalytic Nitrogen Fixation Using Well-Defined Molecular Catalysts under Ambient or Mild Reaction Conditions.

Ammonia (NH3) is industrially produced from dinitrogen (N2) and dihydrogen (H2) by the Haber-Bosch process, although H2 is prepared from fossil fuels, and the reaction requires harsh conditions. On the other hand, microorganisms have fixed nitrogen under ambient reaction conditions. Recently, well-defined molecular transition metal complexes have been found to work as catalyst to convert N2 into NH3 by reactions with chemical reductants and proton sources under ambient reaction conditions. Among them, involvement of both N2-splitting pathway and proton-coupled electron transfer is found to be very effective for high catalytic activity. Furthermore, direct electrocatalytic and photocatalytic conversions of N2 into NH3 have been recently achieved. In addition to catalytic formation of NH3, selective catalytic conversion of N2 into hydrazine (NH2NH2) and catalytic silylation of N2 into silylamines have been reported. Catalytic C-N bond formation has been more recently established to afford cyanate anion (NCO-) under ambient reaction conditions. Further development of direct conversion of N2 into nitrogen-containing compounds as well as green ammonia synthesis leading to the use of ammonia as an energy carrier is expected.

Elevating Discharge Voltage of Li2CO3-Routine Li-CO2 Battery over 2.9†V at an Ultra-Wide Temperature Window.

The Li-CO2 batteries utilizing greenhouse gas CO2 possess advantages of high energy density and environmental friendliness. However, these batteries following Li2CO3-product route typically exhibit low work voltage (<2.5 V) and energy efficiency. Herein, we have demonstrated for the first time that cobalt phthalocyanine (CoPc) as homogeneous catalyst can elevate the work plateau towards 2.98 V, which is higher than its theoretical discharge voltage without changing the Li2CO3-product route. This unprecedented discharge voltage is illustrated by mass spectrum and electrochemical analyses that CoPc has powerful adsorption capability with CO2 (-7.484 kJ mol-1) and forms discharge intermediate of C33H16CoN8O2. Besides high discharge capacity of 18724 mAh g-1 and robust cyclability over 1600 hours (1000 mAh g-1 cut-off) at a current density of 100 mA g-1, the batteries show high temperature adaptability (-30-80 °C). Our work is paving a promising avenue for the progress of high-efficiency Li-CO2 batteries.

Optically Controlled Recovery and Recycling of Homogeneous Organocatalysts Enabled by Photoswitches.

We address a critical challenge of recovering and recycling homogeneous organocatalysts by designing photoswitchable catalyst structures that display a reversible solubility change in response to light. Initially insoluble catalysts are UV-switched to a soluble isomeric state, which catalyzes the reaction, then back-isomerizes to the insoluble state upon completion of the reaction to be filtered and recycled. The molecular design principles that allow for the drastic solubility change over 10 times between the isomeric states, 87 % recovery by the light-induced precipitation, and multiple rounds of catalyst recycling are revealed. This proof of concept will open up opportunities to develop highly recyclable homogeneous catalysts that are important for the synthesis of critical compounds in various industries, which is anticipated to significantly reduce environmental impact and costs.

Honeycomb reactor: a promising device for streamlining aerobic oxidation under continuous-flow conditions.

We report on the high potential of a honeycomb reactor for the use in aerobic oxidation under continuous-flow conditions. The honeycomb reactor is made of porous material with narrow channels separated by porous walls allowing for high density accumulation in the reactor. This structure raised the mixing efficiency of a gas-liquid reaction system, and it effectively accelerated the aerobic oxidation of benzyl alcohols to benzaldehydes under continuous-flow conditions. This reactor is a promising device for streamlining aerobic oxidation with high process safety because it is a closed system.

The use of cosolvents in heterogeneously and homogeneously catalysed methanolysis of oil.

The paper describes transesterification of oil by methanol with use of cosolvents such as ethyl acetate, tetrahydrofuran, hexane, acetone and diethyl ether at catalyst homogeneous (potassium hydroxide) and heterogeneous (mixed oxides). The cosolvents dissolve oil and methanol to form a single (homogeneous) phase, which increases the reaction rate. Therefore, the biodiesel production will be environmentally friendly because less energy is consumed, which increases sustainability. The whole binodal curve of ternary plots of oil, methanol and cosolvent was determined to find the molar ratio, in which the reaction mixture forms a single phase. The ethyl acetate and tetrahydrofuran have relatively small heterogeneous region, because of the similarity of their electric dipole moment with methanol. After transesterification, the detailed analysis of ester and also glycerol phase was carried out. For homogeneous catalyst, the highest esters content in the ester phase was achieved with tetrahydrofuran. For heterogeneous catalyst, the ester content was lower with cosolvent than without cosolvent, probably due to dilution of reaction components by cosolvent or bonding of cosolvent to the active sites of the catalyst.

Efficient Conversion of Carbon Dioxide with Si-Based Reducing Agents Catalyzed by Metal Complexes and Salts.

Homogeneous metal complex and salt catalysts were developed for the reductive transformation of CO2 with Si-based reducing agents. Cu-bisphosphine complexes were found to be excellent catalysts for the hydrosilylation of CO2 with polymethylhydrosiloxane (PMHS). The Cu complexes also showed high catalytic activity and a wide substrate scope for formamide synthesis from amines, CO2 , and PMHS. Simple fluoride salts such as tetrabutylammonium fluoride acted as good catalysts for the reductive conversion of CO2 to formic acid in the presence of hydrosilane, disilane, and metallic Si. Based on the kinetics, isotopic experiments, and in-situ NMR measurements, the reaction mechanism for both catalyst systems, the Cu complex and the fluoride salt, have been proposed.

New Insights into Aldol Reactions of Methyl Isocyanoacetate Catalyzed by Heterogenized Homogeneous Catalysts.

The Hayashi-Ito aldol reaction of methyl isocyanoacetate (MI) and benzaldehydes, a classic homogeneous Au(I)-catalyzed reaction, was studied with heterogenized homogeneous catalysts. Among dendrimer encapsulated nanoparticles (NPs) of Au, Pd, Rh, or Pt loaded in mesoporous supports and the homogeneous analogues, the Au NPs led to the highest yield and highest diastereoselectivity of products in toluene at room temperature. The Au catalyst was stable and was recycled for at least six runs without substantial deactivation. Moreover, larger pore sizes of the support and the use of a hydrophobic solvent led to a high selectivity for the trans diastereomer of the product. The activation energy is sensitive to neither the size of Au NPs nor the support. A linear Hammett plot was obtained with a positive slope, suggesting an increased electron density on the carbonyl carbon atom in the rate-limiting step. IR studies revealed a strong interaction between MI and the gold catalyst, supporting the proposed mechanism, in which rate-limiting step involves an electrophilic attack of the aldehyde on the enolate formed from the deprotonated MI.

Dinuclear Metal Synergistic Catalysis Boosts Photochemical CO2 -to-CO Conversion.

The solar-driven CO2 reduction is a challenge in the field of "artificial photosynthesis", as most catalysts display low activity and selectivity for CO2 reduction in water-containing reaction systems as a result of competitive proton reduction. Herein, we report a dinuclear heterometallic complex, [CoZn(OH)L1 ](ClO4 )3 (CoZn), which shows extremely high photocatalytic activity and selectivity for CO2 reduction in water/acetonitrile solution. It achieves a selectivity of 98 % for CO2 -to-CO conversion, with TON and TOF values of 65000 and 1.8 s-1 , respectively, 4, 19, and 45-fold higher than the values of corresponding dinuclear homometallic [CoCo(OH)L1 ](ClO4 )3 (CoCo), [ZnZn(OH)L1 ](ClO4 )3 (ZnZn), and mononuclear [CoL2 (CH3 CN)](ClO4 )2 (Co), respectively, under the same conditions. The increased photocatalytic performance of CoZn is due to the enhanced dinuclear metal synergistic catalysis (DMSC) effect between ZnII and CoII , which dramatically lowers the activation barriers of both transition states of CO2 reduction.

Copper-Catalyzed Arylation of Remote C(sp3 )-H Bonds in Carboxamides and Sulfonamides.

Reported herein is an unprecedented copper-catalyzed arylation of remote C(sp3 )-H bonds. Stirring a trifluorotoluene solution of either N-fluorocarboxamides or N-fluorosulfonamides and arylboronic acids in the presence of a catalytic amount of copper(II) trifluoroacetylacetonate, 2,2'-bipyridine, and sodium tert-butoxide afforded the γ- and δ-C(sp3 )-H arylated carboxamides and sulfonamides, respectively, in good to high yields. Mechanistic studies indicate that the reaction might proceed through an amidyl radical generation, 1,5-hydrogen atom transfer (HAT), and copper-catalyzed cross-coupling of the resulting carbon radical with arylboronic acids.

Bimetallic Chromium Catalysts with Chain Transfer Agents: A Route to Isotactic Poly(propylene oxide)s with Narrow Dispersities.

Bimetallic chromium catalysts are investigated for the enantioselective polymerization of propylene oxide. The catalyst is composed of two salen chromium species linked by an alkyl chain, the length of which significantly impacts the rate of polymerization. While the use of a chloride initiator on the catalyst resulted in bimodal molecular weight distributions, switching to a trifluoroacetate initiating group and adding a diol chain transfer agent afforded polymers of controllable molecular weight with low, unimodal dispersities.

Copper-Catalyzed Enantioselective Domino Arylation/Semipinacol Rearrangement of Allylic Alcohols with Diaryliodonium Salts.

A copper-catalyzed enantioselective arylative semipinacol rearrangement of allylic alcohols was developed. In the presence of a catalytic amount of an in situ generated chiral copper-bisoxazoline complex, reaction of allylic alcohols with diaryliodonium salts afforded spirocycloalkanones in high yields with high diastereo- and enantioselectivities. A two-point binding model engaging the carbon-carbon double bond and the proximal hydroxyl group was proposed to be responsible for the highly efficient chirality transfer.

Catalytic Enantioselective Double Carbopalladation/C-H Functionalization with Statistical Amplification of Product Enantiopurity: A Convertible Linker Approach.

Combining a catalytic enantioselective reaction with dimerization in a single operation is an efficient way to upgrade the enantiomeric excesses (ee) of the product. Palladium-catalyzed reaction of N-(2-iodophenyl)-N-methyl methacrylamide derivatives with oxadiazole afforded, by a double enantioselective carbopalladation/intermolecular heteroarene C-H alkylation sequence, homodimers in good yields with excellent ee values. The dimer was subsequently elaborated to the monomer in which the linker (oxadiazole) was incorporated into the target product.

Exploring bis(cyclometalated) ruthenium(II) complexes as active catalyst precursors: room-temperature alkene-alkyne coupling for 1,3-diene synthesis.

Described is the development of a new class of bis(cyclometalated) ruthenium(II) catalyst precursors for C-C coupling reactions between alkene and alkyne substrates. The complex [(cod)Ru(3-methallyl)2] reacts with benzophenone imine or benzophenone in a 1:2 ratio to form bis(cyclometalated) ruthenium(II) complexes (1). The imine-ligated complex 1 a promoted room-temperature coupling between acrylic esters and amides with internal alkynes to form 1,3-diene products. A proposed catalytic cycle involves C-C bond formation by oxidative cyclization, ß-hydride elimination, and C-H bond reductive elimination. This Ru(II)/Ru(IV) pathway is consistent with the observed catalytic reactivity of 1 a for mild tail-to-tail methyl acrylate dimerization and for cyclobutene formation by [2+2] norbornene/alkyne cycloaddition.

An Electrolyte Engineered Homonuclear Copper Complex as Homogeneous Catalyst for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries suffer from severe polysulfide shuttle, retarded sulfur conversion kinetics and notorious lithium dendrites, which has curtailed the discharge capacity, cycling lifespan and safety. Engineered catalysts act as a feasible strategy to synchronously manipulate the evolution behaviors of sulfur and lithium species. Herein, a chlorine bridge-enabled binuclear copper complex (Cu-2-T) is in situ synthesized in electrolyte as homogeneous catalyst for rationalizing the Li-S redox reactions. The well-designed Cu-2-T provides completely active sites and sufficient contact for homogeneously guiding the Li2S nucleation/decomposition reactions, and stabilizing the lithium working interface according to the synchrotron radiation X-ray 3D nano-computed tomography, small angle neutron scattering and COMSOL results. Moreover, Cu-2-T with the content of 0.25 wt% approaching saturated concentration in electrolyte further boosts the homogeneous optimization function in really operated Li-S batteries. Accordingly, the capacity retention of the Li-S battery is elevated from 51.4% to 86.3% at 0.2 C, and reaches 77.0% at 1.0 C over 400 cycles. Furthermore, the sulfur cathode with the assistance of Cu-2-T realizes the stable cycling under the practical scenarios of soft-packaged pouch cell and high sulfur loading (6.5 mg cm-2 with the electrolyte usage of 4.5 µL mgS -1).

Production of biodiesel from waste fish fat through ultrasound-assisted transesterification using petro-diesel as cosolvent and optimization of process parameters using response surface methodology.

Biodiesel is a highly promising and viable alternative to fossil-based diesel that also addresses the urgent need for effective waste management. It can be synthesized by the chemical modification of triglycerides sourced from vegetable origin, animal fat, or algal oil. The transesterification reaction is the preferred method of producing biodiesel. However, the non-miscibility of alcohol and oil layer causes excessive utilization of alcohol, catalyst, and a substantial reacting time and temperature. In the current investigation, transesterification of waste fish oil was performed with petro-diesel as cosolvent, under the influence of ultrasound energy. The combination of both techniques is a unique and efficient way to minimize the mass transfer limitations considerably and hence reduces the parameters of the reaction. It is also a sincere effort to comply with the principles of green chemistry. The optimum reaction conditions were obtained using response surface methodology (RSM) that were as follows: molar ratio of methanol to oil 9.09:1, catalyst concentration of 0.97 wt%, cosolvent concentration of 29.1 wt%, temperature 60.1℃, and a reacting time 30 min. Under these listed conditions, 98.1% biodiesel was achievable, which was in close agreement with the expected result. In addition, the cosolvent removal step from the crude biodiesel was also eliminated as it could be employed as a blended fuel in CI engines.

Hydrothermal liquefaction of lignocellulosic biomass with potassium phosphate and iron and their binary mixture: A comprehensive investigation on the yields and compositions of biocrude and solid residue.

Hydrothermal liquefaction of corn, soybean, rice and wheat straws with K3PO4, Fe and Fe + K3PO4 at 320 °C for 30 min was examined. The addition of K3PO4 led to the highest biocrude yields from hydrothermal liquefaction of rice straws (39.20 wt%). Particularly, the biocrude yields from K3PO4-catalyzed hydrothermal liquefaction of corn and rice straws were âˆ¼ 10 wt% higher than those from non-catalytic run (19.4 and 27.8 wt%). Catalytic hydrothermal liquefaction with K3PO4 had minimal impact on the elemental compositions of biocrudes and solid residue. Furthermore, K3PO4 promoted the enrichment of low-boiling components in biocrudes by 2.02 wt%. for hydrothermal liquefaction of wheat straw. Moreover, the incorporation of K3PO4 induces the occurrence of dense porous structure on the surface of solid residue, making it highly suitable as an adsorbent or catalyst carrier. Finally, potential reaction network and mechanisms of catalytic hydrothermal liquefaction of straw have been proposed and discussed detailly.

Investigation of catalytic reaction of ethylene dimerization to butene-1 by use of DCPDS as a modifier based on response surface methodology.

Butene-1 is one of the most important petrochemical industry products that is produced in different ways. Ethylene is an important source of Butene-1 production through the oligomerization process. In this study, to reduce the by-product of the polymer produced and to improve the catalyst yield, the dicyclopentyldimethoxysilane (DCPDS) modifier in the presence of a homogeneous titanium tetra butoxide/triethyl aluminum catalyst and a combination of dichloromethane (as a promoter) in a high-pressure Buchi reactor were used. Gas chromatography was used for liquid and gas phase analysis in the reactor. The design of experiments was performed with the Box-Behnken design technique (BBD) based on the response surface method (RSM). In this method, four effective factors of catalyst concentration, modifier, promoter, and temperature were evaluated. The results of the analysis of variance for the answers of ethylene conversion rate, selectivity, polymer production rate, and yield showed that there is a good agreement between the actual values and the values obtained from the model. Optimization using design expert software showed values of 85.6, 88.5, 2.43, and 75.78% for ethylene conversion rate, selectivity, polymer content and yield, respectively, which showed an error of less than one percent compared to the laboratory results. Comparison of the catalyst performance with and without DCPDS and DCM showed that the presence of these two compounds together with the catalyst, in addition to increasing by 4, 6, and 9% for conversion, selectivity of Butene-1 and yield, respectively, reduced the production of the undesirable polymer in the reactor from 136 mg to 2.4 mg.

Mechanistic insight into homogeneous catalytic crosslinking behavior between cellulose and epoxide by explicit solvent models.

Inspired by recent advances on functional modification of cellulosic materials, the crosslinking behaviors of epoxide with cellulose under the catalysis of different homogeneous catalysts including H2O, Brønsted acid, Brønsted base, Lewis acid and neutral salt were systematically investigated using density functional theory (DFT) methods with hybrid micro-solvation-continuum approach. The results showed that catalytic activity, reaction mechanism and regioselectivity are determined by the combined effect of catalyst type, electronic effect and steric hindrance. All the homogeneous catalysts have catalytic activity for the crosslinking reaction, which decreases in the order of NaOH > HCl > NCl3 > MCl2 > CH3COOH > NaCl (N = Fe3+, Al3+; M = Zn2+, Ca2+). Upon the catalysis of NaOH, hydroxyl group of cellulose is firstly deprotonated to form a carbanion-like intermediate which will further attack the less sterically hindered C atom of epoxide showing excellent regioselectivity. Acidic catalysts readily cause epoxide protonated, which suffers from nucleophilic attack of cellulose and forms the carbocation-like intermediate. Brønsted acid exhibits poor regioselectivity, however, Lewis acid shows an interesting balance between catalytic activity and regioselectivity for the crosslinking reaction, which may be attributed to the unique catalysis and stabilization effects of its coordinated H2O on the transition state structure.