Lower Reaction Time Research Articles

Bis(pyrazolyl)palladium(II) complexes as catalysts for Mizoroki–Heck cross-coupling reactions

Recent progress in carbon–carbon cross-coupling reactions has resulted in the discovery of highly active catalysts for carrying out such transformations. However, due to the wide array of applications of the products from cross-coupling reactions, there is the need to design suitable catalysts that permit the practical and economical synthesis of the cross-coupled products. Palladium complexes with bulky and electron-donating ligands have served as excellent (pre)catalysts for the Mizoroki–Heck cross-coupling reaction. By using bulky pyrazole-based ligands, we have prepared palladium(II) complexes with controlled steric and electronic properties of the metal center. We have used these bulky bis(pyrazolyl)palladium(II) complexes as (pre)catalysts for the Mizoroki–Heck cross-coupling reaction. The (pre)catalysts displayed high activity and selectivity, giving high catalytic conversions at a low (pre)catalyst loading and short reaction times. A mercury poisoning test confirmed that the (pre)catalysts promoted the Mizoroki–Heck cross-coupling homogenously and do not decompose into palladium black during the reactions. The catalytic systems were also tolerant to the presence of functional groups, such as 4-CF3, 4-CH3, 4-CO2Me and 4-CO2Et, on the alkene substrates.

Synthesis of N-heterocyclic carbene palladium magnetic nanocatalyst and its applications in Suzuki coupling reaction

N-heterocyclic carbene palladium magnetic nanomaterial has been fabricated by complexing Pd (Ⅱ) to the surface of the Fe3O4 modified with N-heterocyclic carbene. Successful synthesis has been verified by TEM, EDX, FT-IR, XRD, XPS, AAS, TGA and VSM. The composites were then applied to Suzuki coupling reaction. To select a highly efficient and environment-friendly reaction strategy, mixed solvent of ethanol and water ethanol (1:1) were used as the reaction solvent. The catalyst exhibits excellent performance, and most of the substrates can obtain high yields at low reaction temperature and short reaction time. In addition, due to the excellent magnetic properties of the catalyst, it can be recycled by simple magnetic separation and washing. It remains also a good reaction yield after ten times of repeated use.

Ultrafast hydrolysis of inulin in supercritical water: Fructooligosaccharides reaction pathway and Jerusalem artichoke valorization

In a biorefinery approach, inulin and inulin-rich biomass as Jerusalem artichoke (JA) could be transformed into platform chemicals such as fructose and/or pyruvaldehyde. To do so, the FASTSUGARS pilot plant proved to be a promising alternative for the selective conversion of biomass. In this work, inulin and JA were hydrolyzed in supercritical water (SCW) for the first time. Commercial inulin was selected as a model for fructooligosaccharides (FOS) and its reaction pathway in SCW was elucidated. It was found that fructose was the primary product from FOS hydrolysis in SCW, which was then selectively transformed into pyruvaldehyde as reaction time increased. Operating with extremely low reaction times (0.12 s) the sugars selectivity of JA was as high as 76% w/w. In both cases, the production of degradation products such as 5-HMF and acids was very low. Finally, comparing JA results to those from lignocellulosic biomass it was found that higher conversion was achieved in the case of JA due to its inulin-based composition.

Effects of training on sensitivities to spatial changes in auditory scenes

Previous work has shown that change deafness can occur with changes in the spatial location of objects within auditory scenes. Whether performance can be improved with training has yet to be directly tested. In the present study, the impact of training was examined in a “flicker”-like paradigm, where an initial scene comprising environmental sounds presented on the horizontal plane alternated with the presentation of a comparison scene, which was either the same or contained a change in the location of one or more sounds. Trained participants were trained on a set of sounds on day 1, while control subjects completed an unrelated visual task. On day 2, participants were tested using the same paradigm, with trained subjects hearing either the sounds they were trained on or new sounds, and controls being exposed to the paradigm for the first time. Overall, trained participants performed better (93% accuracy) than untrained participants (79%). Both groups had lower reaction times on correct-response change trials than on correct-response no-change trials. Trained subjects performed no better on trained sounds than new sounds. These data indicate that training can improve task performance, but improvements may be not be limited to sounds experienced during training.Previous work has shown that change deafness can occur with changes in the spatial location of objects within auditory scenes. Whether performance can be improved with training has yet to be directly tested. In the present study, the impact of training was examined in a “flicker”-like paradigm, where an initial scene comprising environmental sounds presented on the horizontal plane alternated with the presentation of a comparison scene, which was either the same or contained a change in the location of one or more sounds. Trained participants were trained on a set of sounds on day 1, while control subjects completed an unrelated visual task. On day 2, participants were tested using the same paradigm, with trained subjects hearing either the sounds they were trained on or new sounds, and controls being exposed to the paradigm for the first time. Overall, trained participants performed better (93% accuracy) than untrained participants (79%). Both groups had lower reaction times on correct-response change tr...

Rate accelerations with zeolite Y in the synthesis of octahydro xanthenes and benzoxanthenes and their simple bio assay data

Abstract Zeolite Y (CBV-720) has been accomplished as an efficient, easily available and eco-friendly catalyst for one pot synthesis of 1, 8-Dioxo-octahydroxanthene and 14-aryl -14H dibenzo [a, j] xanthenes with 5, 5-dimethyl-1, 3- cyclohexanedione or 2-OH naphthol with different substituted aryl aldehydes under neat (solvent free) at 110 0C and microwave conditions. This protocol offers simple cyclocondensation, excellent yields, low reaction time, low amount reusable catalyst and simple operational procedures and free from adverse solvents.

Phosphotungstic acid supported on SiO2@NHPhNH2 functionalized nanoparticles of MnFe2O4 as a recyclable catalyst for the preparation of tetrahydrobenzo[b]pyran and indazolo[2,1-b]phthalazine-triones

MnFe2O4@SiO2@NHPhNH2–phosphotungstic acid was synthesized by the reaction of diamine-modified silica coated manganese ferrite nanoparticles with H3PW12O40, the Keggin-type heteropoly acid. This is the first time that H3PW12O40 supported on diamine functionalized MnFe2O4 nanoparticles has been reported. The synthesized catalyst was characterized by various techniques, including Fourier Transform Infrared Spectroscopy (FTIR), Transmission electron-microscopy (TEM), X-ray Powder Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), Thermogravimetric Analysis (TGA), and Vibrating Sample Magnetometer (VSM). The synthesized nanoparticle was examined as the heterogenous nanocatalyst for the synthesis of tetrahydrobenzo-[b]-pyran derivatives and 2H-indazolo-[2,1-b]-phthalazine-triones under the solvent-free heating or ultrasonic irradiation conditions. This method offers several advantages including high yield, low reaction times, and the simple work-up procedure due to the presence of the magnetic nanoparticles in this catalyst, so that, it can be easily recovered and reused for at least six successive times without the loss of its high catalytic activity, suggesting its great Potential for industrial applications.

Utilization of eggshell waste as green catalyst for application in the synthesis of 1,2,4,5-tetra-substituted imidazole derivatives

Eggshell as a solid waste was loaded on a nano-Fe3O4 surface. Then, in one step, it (Fe3O4@eggshell) was converted to Fe3O4@Ca3(PO4)2 as a nano-magnetic, green, cheap, and environmentally friendly catalyst. Techniques such as FT-IR, VSM, FESEM, TEM, EDX, XRD, and TGA were used to characterize the as-synthesized catalyst. The catalytic activity of Fe3O4@Ca3(PO4)2 was evaluated in the synthesis of 1,2,4,5-tetra-substituted imidazole derivatives through a one-pot multicomponent reaction. The design of the experiment as a systematic statistical approach was used to obtain the optimum point of the reaction condition so that 0.05 g of the as-synthesized catalyst and 94.77 °C were the best condition (which provides 90% yield for the benchmark reaction). Then, 1,2,4,5-tetra-substituted imidazole derivatives in the optimum condition were synthesized with very low reaction times in good yields. The as-prepared catalyst was retrieved through a magnet and used several times without significant loss of catalytic activity.

Cross-domain correlates of cannabis use disorder severity among young adults

BackgroundCorrelates of cannabis use and dependence among young adults have been widely studied. However, it is not known which factors are most strongly associated with severity of cannabis use dependence (CUD) severity. Identification of the salient correlates of CUD severity will be of increasing clinical significance as use becomes more socially normative. MethodsThis study used a data-driven, hypothesis-free approach to examine the most robust correlates of CUD severity among a sample of 76 young adults (ages 18 to 25 years) who used cannabis at least weekly. Seventy-one candidate variables were examined for association with CUD severity. These included demographic variables, self-reported and psychodiagnostic assessments of mood and anxiety, self-reported measures of personality, cannabis and other substance use characteristics, and objective and subjective measures of cognition. ResultsOf the 71 candidate variables considered, 27 were associated with CUD severity on a univariate level at a p-value ≤.20. Correlates of CUD severity in the multivariable model using stepwise selection were: more frequent cannabis use in the past 90 days, greater expectancies that cannabis causes cognitive and behavioral impairment, greater self-reported metacognitive deficits, greater anxiety, and lower reaction time variability on a test of sustained attention. Internal validation tests support high prediction accuracy of all variables in the multivariable model, except for lower reaction time variability. ConclusionsCannabis use frequency, beliefs about use, perceived cognitive abilities, and anxiety are robustly associated with CUD severity in young adult, regular cannabis users, and may be important in guiding prevention and treatment efforts.

Magnetic Fe3O4-supported sulfonic acid-functionalized graphene oxide (Fe3O4@GO-naphthalene-SO3H): a novel and recyclable nanocatalyst for green one-pot synthesis of 5-oxo-dihydropyrano[3,2-c]chromenes and 2-amino-3-cyano-1,4,5,6-tetrahydropyrano[3,2-c]quinolin-5-ones

Synthesis of a novel magnetic 1-naphthalenesulfonic acid-grafted graphene oxide (Fe3O4-GO-naphthalene-SO3H) via a three-step procedure has been described. The structure of this newly synthesized nanographene oxide was fully characterized by X-ray diffraction, energy dispersive X‐ray, vibrating sample magnetometer, scanning electron microscopy, Fourier-transform infrared, Raman spectroscopy, and thermo-gravimetric analytical techniques. The catalytic efficiency of these nanoparticles as recyclable nanocatalyst was explored in one-pot three-component reaction between aldehydes, malononitrile, and 4-hydroxyquinolin-2(1H)-one or 4-hydroxycoumarin under green conditions in water for the synthesis of 2-amino-3-cyano-1,4,5,6-tetrahydropyrano[3,2-c]quinolin-5-ones and 5-oxo-dihydropyrano[3,2-c]chromenes (coumarins) respectively. High yields of the products, low reaction times, easy preparation of the catalyst, and use of water as green solvent are the main advantages of this protocol. In addition, the catalyst can be easily separated simply by using a magnet and reused for six fresh runs without significant loss of activity.

Effect of Preheating Temperature and Extraction Pressure on Combustion Characteristics of Cake from Whole, Kernels and Crushed Jatropha Seed

The Low heating value, reaction time, burning temperature and gas emission of jatropha seed cake respectively from whole, kernel and crushed seeds preheated at 25°, 50°, 75° and 100°C temperature and under 8400, 15000 and 19500 pounds pressure levels were assessed. At this effect, the combustion process consisted in introducing 20 g of each cake sample type into a one liter volume burning chamber and 130 g of water also into one liter water compartment of a designed combustion unit. The main results were as follow. The highest lower Heating value (21,51±93,64 MJ/kg) was obtained with the cake from crushed seeds preheated at 100°C and under of 15000 pounds pressure. The highest reaction time (1072,66±153,44 seconds) was registered with cake from kernel seeds also preheated at 100°C but with 19500 pounds pressure. The highest burning temperature was recorded from the whole jatropha seed cake. The highest carbon monoxide level ( ) was recorded during crushed and whole seeds cake combustion while the carbon dioxide level was the highest with the kernel seed cake.

Mild reaction conditions induce high sugar yields during the pretreatment of Agave tequilana bagasse with 1-ethyl-3-methylimidazolium acetate

Sequential 2k factorial and central composite designs were used to optimize Agave tequilana bagasse (ATB) pretreatment by using 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]). Reaction time, temperature and solids loading were the studied factors while sugar yield was the response variable. Results indicated that optimal conditions (119 °C, 142 min) using high solids loading (30%) were achieved at lower temperatures and reaction times than those previously reported in the literature. It was also revealed that solid recovery after pretreatment with [Emim][OAc] is a key factor. The increase in enzymatic digestibility of pretreated ATB was correlated to a decrease in crystallinity and lower lignin content as observed using microscopy techniques and weaken chemical bonds by Fourier transform infrared spectroscopy. Yields of glucose and xylose in the hydrolysate were 41.3, and 13.0 kg per 100 kg of untreated ATB, which are equivalent to glucan and xylan conversions of 75.9% and 82.9%, respectively.

Intensification of hydrogen adsorption by novel Cu-BDC@rGO composite material synthesized in a microwave-assisted circular micro-channel

In this study, pure Cu-BDC and composite Cu-BDC@rGO were produced by combining microwave irradiation and microfluidics (MW-assisted microfluidic) to intensify the hydrogen adsorption. To compare two heating methods, pure Cu-BDC was synthesized by both MW-assisted microfluidic and conventional heating methods. Results showed that the production yield and hydrogen adsorption capacity of Cu-BDC was 18% and 26% greater for MW-assisted microfluidic heating, respectively. In addition to the results, this method brings some advantageous such as lower reaction time, lower reactor size, more uniform crystal shape, and lower crystal size compared to conventional heating. So, the MW-assisted microfluidic method was selected for further investigations. Response surface method (RSM) applied to find the optimum synthesis condition of the material for hydrogen uptake. In this regard, GO content, metal/linker molar ratio, and microwave (MW) time selected as independent, and the hydrogen adsorption at 77 K and 40 bar selected as the dependent response. Also, experiments showed that the one pot synthesis of Cu-BDC@rGO (sandwich-like adsorbent) has the best hydrogen uptake compared to pure Cu-BDC (cubic adsorbent) and the other sample (worm-like adsorbent) which is confirmed the effect of modulating synthesis route. Finally, it must be said that the incorporation of GO and MW-assisted microfluidic heating improved the specific surface area, pore volume, throughput, and thermal stability of the adsorbent.

Ultrasonic Accelerated Biginelli‐Like Reaction by the Covalently Anchored Copper‐Isatoic Anhydride over the Modified Surface of Mesoporous SBA‐15 to the Synthesis of Pyrimidines

AbstractThe novel hybrid catalyst Cu@IA‐SBA‐15 was synthesized by anchoring isatoic anhydride on amino‐functionalized SBA‐15. The synthesized process pursued by grafting of Cu(II) to catch desired product. 2D‐hexagonally ordered mesoporous of bidentate ligand characterized by X‐ray diffraction spectroscopy (XRD), N2 adsorption analysis, Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), fourier‐transform infrared spectroscopy (FTIR), Energy‐dispersive X‐ray spectroscopy (EDX), and Thermogravimetric and differential thermal analysis (TGA‐DTA). The activity of catalyst has been scrutinized in Biginelli‐Like reaction through the environmentally benign conditions by using ultrasound irradiation and green solvents. The methodology offers remarkable development by easy production of hybrid catalyst Cu@IA‐SBA‐15 in regard to solve the problem of using harsh catalysts. It also demonstrates to be impressive and environmentally friendly in term of low reaction times and high yields.

Fuel effects on Li2CuP2O7 synthesized by solution combustion method for lithium-ion batteries

Lithium copper pyrophosphate has been synthesized by the solution combustion method for the first time. Urea and hexamethylenetetramine were used as fuel. The samples were successfully prepared in low reaction temperature and short reaction time. The products were structurally characterized by FT-IR and p-XRD. Thermal behavior of samples was also investigated through TG/DT analyses. Magnetic measurements showed that the urea- and hexamethylenetetramine-assisted Li2CuP2O7 were paramagnetic at room temperature. Surface analyses indicated that the fuel types changed the surface properties of samples because of exothermic redox reaction during combustion, and electrochemical performances showed clear differences. The charge capacity of urea- and hexamethylenetetramine-assisted synthesized Li2CuP2O7 was calculated as 180 mAhg−1 and 146 mAhg−1. Synthesis method enlarged the charge capacity and prepared lithium copper pyrophosphate to have a potential for use in lithium-ion batteries.

Emotional processing in RRMS patients: Dissociation between behavioural and neurophysiological response

BackgroungMultiple sclerosis (MS) results in a broad range of symptoms, including motor, visual, cognitive, and neuropsychiatric deficits. Some studies, considering affective facial expressions to study emotion processing, demonstrated emotion recognition difficulties in MS patients. ObjectiveWe investigated the impact of MS on the emotional-behaviour rating and neurophysiological response (Event Related Potentials-ERP) through a battery of affective visual stimuli selected from the International Affective Picture System (IAPS). MethodsTwenty patients with diagnosis of Relapsing Remitting MS (RRMS) and 20 Healthy Controls (HC) matched by age, gender and education were enrolled. Each of them, after a neuropsychological assessment, were asked to evaluate arousal and valence of affective visual stimuli. ResultsOur results showed higher P300 amplitudes in RRMS patients than HC group for pleasant and unpleasant images. Moreover, RRMS patients showed lower Reaction Time (RT) respect HC in valence rating. No other effect did emerge between groups. ConclusionOur study shows early compensatory cerebral mechanisms in RRMS patients throughout emotional information processing, particularly for unpleasant and pleasant stimuli. We hypothesize that this compensatory cerebral mechanism reduces the behavioural dissimilarity between patients and HC.

Cu2O modified g-C3N4 as an effective catalyst for the synthesis of propargylamines: experimental, quantum mechanical mechanistic and kinetic study

In this research, graphite-like carbon nitride (g-C3N4) was prepared via a common method i.e. one-step thermal polycondensation of urea and then modified by copper (I) oxide. After that, the as-prepared g-C3N4/Cu2O composite was used as the superior catalyst for effective coupling reaction between arylaldehydes, alkynes and secondary amines in the formation of wide range of propargylamine derivatives. The new, efficient catalyst was characterized using different techniques including Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The reactions were performed in nearly low reaction times, and the products were obtained in moderate to high yields. At the end of the transformation, using by simple filtration, the catalyst was separated from reaction mixture and reused for four times with minimum loss of activity. The catalyst is simple to prepare and shows higher catalytic activity than some recently reported catalysts. Moreover, the potential energy surface (PES) of the reaction has been studied by density functional theory (DFT) and it was realized that the first step of the reaction, that is, separation of acetylenic hydrogen shows a primary kinetic isotope effect and hence is the rate determining step of the reaction.

Copper incorporated into 1H-1,2,3-triazole-5-methanol functionalized halloysite nano clay as an efficient and heterogeneous catalyst for promoting green A3 and KA2 coupling reaction: Optimization of reaction variables using response surface methodology

Abstract Design and synthesis of a novel heterogeneous catalyst based on functionalization of halloysite nanoclay with 1H-1,2,3-triazole-5-methanol and subsequent incorporation of copper is disclosed. The obtained catalyst was fully characterized by employing ICP-AES, SEM/EDX, TGA, XRD, BET and FTIR and successfully used for promoting the A3 and KA2 coupling reactions of phenylacetylene, amines and aldehydes or ketone in aqueous media. The reaction variables including reaction temperature and amount of the catalyst were optimized using Response Surface Methodology (RSM). The catalyst exhibited excellent catalytic activity under optimum reaction condition. Notably, the investigation of the reusability of the catalyst confirmed that the catalyst could be recovered and reused up to four reaction runs with only slight loss of the catalytic activity. The hot filtration experiment also demonstrated low leaching of copper species, indicating the heterogeneous nature of the catalysis. Easy work-up procedures, performing the reaction in aqueous media, broad range of substrate scope and low reaction times are other merits of this protocol.

Verkade's Superbase as an Organocatalyst for the Strecker Reaction

Proazaphosphatranes ‐Verkade's superbases‐ proved to be efficient organocatalysts for the Strecker reaction between protected imines and trimethylsilyl cyanide (TMSCN). Excellent to quantitative yields were reached and, compared to other systems, only low catalyst loading and short reaction times were required for the reaction to proceed efficiently. A remarkable initial turnover frequency (TOF), close to 105 h–1, was achieved, associated with an excellent selectivity since no side reactions were observed. A reaction mechanism was proposed and the key role played by the apical nitrogen in the proazaphosphatrane structure was demonstrated.

Evaluation of Lipases from Wild Microbial Strains as Biocatalysts in Biodiesel Production

In this study, the evaluation of the catalytic behavior of several wild bacterial strains in the 1,3-selective ethanolysis of triglycerides with ethanol to produce a new type of biodiesel (Ecodiesel) that integrates glycerol as monoacylglycerols was carried out. The Ecodiesel production not only avoids the elimination of glycerol, which is largely generated as a by-product in the biodiesel industry, but also results in an increase in the biofuel yield. The wild microbial strain samples were obtained from several lipophilic organisms. In addition to evaluate the enzymatic extracts, the minimum grade of purification of the strains, necessary to obtain similar results to those attained with commercial lipases was studied. This purification treatment included a dialysis followed by a lyophilization process. Such extracts were directly used as biocatalysts in the transesterification reaction of sunflower oil with ethanol, attaining much better results (yield close to 100%) than those obtained with strains which were not submitted to the purification process (yields lower than 10%). Furthermore, the results here obtained are similar to those obtained with commercial lipases but were achieved under mild conditions and lower reaction time (2 h). In addition, the stability of the enzymatic extracts was corroborated by subsequent reactions, showing no loss of activity. Thus, this study brings to light that enzymatic extracts obtained by a very simple purification process can be economically competitive with the conventional biodiesel production methods.

Differences in selected coordinaton abilities between pupils with communication ability disorder and able-bodied pupils

Abstract The aim of the study was to analyse and compare the level of selected coordination abilities of pupils with communication ability disorder (CAD) and able-bodied pupils in the same age category. Two groups of participants were recruited for the study: (1) pupils attending special elementary school for children with CAD (n = 17; 5 girls and 12 boys in mean age 11.2 ± 0.7 years), (2) and ablebodied pupils (n = 20; 12 girls and 8 boys in mean age 11.4 ± 0.5 years) without gender differentiation. 5 standardised tests measuring coordination abilities were used as a primary research method (Šimonek 2015): low jump test, spatial orientation ability test, circles through running test, one leg stand test, catching ball test. Group differences were analysed with Mann-Whitney U-test for independent samples. The level of significance was α < 0.05. We found significantly higher level of spatial orientation ability and static balance displayed by able-bodied pupils comparing pupils with CAD. The level of lower limb kinaesthetic discrimination ability, rhythmic ability, frequency and reaction time in pupils with CAD are comparable to the level of able-bodied pupils. We recommend that children with CAD should participate in regular physical activities and sports after compulsory education together with able-bodied children to improve their fine and gross motor ability, coordination abilities as well as overall physical fitness.