Ketones In Yields Research Articles

Double nonmetal elements modified porous TiO2 homogeneous junction for efficient photocatalytic oxidation of cyclohexane

The nitrogen-doped TiO2 with mesoporous structure, anatase/rutile homogeneous junction and surface carbon species were successfully synthesized by facile hydrolysis of tetrabutyl titanate and preheating under the sealed condition, followed by a urea-aided calcination process. Interestingly, the as-obtained carbon modified TiO2 intermediates prepared by pretreating at different temperatures showed a certain photocatalytic activity for cyclohexane oxidation, and the carbon species were deposited to the surfaces of TiO2 via the Ti-O-C bond. The microstructure and photocatalytic activity of the double nonmetal elements modified porous mixed-phase TiO2 microspheres were found to depend on the preheating conditions, and nitrogen was doped into TiO2 lattice, the co-modification of nitrogen and carbon jointly improved the light absorption capacity and reduced the band gap of TiO2. The construction of a mixed-phase junction further improved the photocatalytic performance of the co-modified TiO2 compared with pure anatase or rutile TiO2. The optimal catalyst (N-TiO2-3 b) displayed efficient and stable photocatalytic performance for three cycles. When the reaction was conducted in real outdoor circumstances, the high ketone yield (206.22 μmol) and selectivity (99.92 %) were achieved. The synthetic method was simple and cheap, thus this work showed great potential for green production of fine chemicals under moderate conditions.

Copper‐cobalt bimetallic nanoparticles for the acceptorless dehydrogenation of alcohols: a combined experimental and theoretical study.

Bimetallic Cu and Co nanoparticles were prepared using the polyol process. The nature of the polyol was found to be decisive to control the distribution of the two metals within the particles, resulting in either core‐shell or quasi‐alloyed structures, as shown by chemical analysis at the single particle level. The particles can be prepared over the entire composition range with a very good control of the Cu/Co molar ratio. The introduction of Cu in the synthetic system allows decreasing significantly the mean size of the resulting particles. The two sets of particles were used as unsupported catalysts for the solvent‐free acceptorless dehydrogenation of octan‐2‐ol. Very good ketone yields were measured when using the quasi‐alloyed particles while lower activities were obtained with core‐shell structures. The Cu25Co75 quasi‐alloyed catalyst could be recycled at least ten times without a significant loss in catalytic activity and particle‐scale chemical analyses confirmed that the recovered particles are still alloyed with no observed demixing. The catalytic results are discussed in the light of different exposed metal surface areas and possible synergetic effects using theoretical predictions.

Catalytic Ketonization over Oxide Catalysts (Part XIV): The Ketonization and Cross-Ketonization of Anhydrides, Substituted Acids and Esters

A series of 20 wt.% MO2/S catalysts (where M = Ce, Mn or Zr and S = SiO2 or Al2O3) were prepared using various precursors of the active phases. The resulting catalysts were characterized using different methods (XRD, TPR and SBET). For the first time, anhydrides were used as potential starting materials for ketone synthesis. This novel reaction was performed on various aliphatic anhydrides in the presence of catalysts within a temperature range of 523–723 K. For all anhydrides, except for pivalic anhydride, the appropriate ketones were obtained with good or very good yields. The vapor-phase catalytic ketonization of esters of benzene-1,x-dicarboxylic acids (x = 2, 3 or 4) with acetic acid were studied in the range of 673–723 K in order to obtain 1,x-diacetylbenzenes. Their yields strongly increased with an increase in the x value (0, 8 and 43% for x = 2, 3 and 4, respectively). The presence of acetophenone as a side product was always noted. In the case of ω-phenylalkanoic acids, their vapor-phase ketonization with acetic acid led to the formation of appropriate ketones with 47–49% yields. Much lower yields of ketones (3–19%) were obtained for acids and ethyl esters containing heterocycle substituents (with O or S atoms) and/or vinyl groups. In the reaction between ethyl 4-nitrophenylacetate and acetic acid, only the products of ester decomposition (p-toluidine and p-nitrotoluene) were determined.

Synthesis of ω-functionalized ketones from strained cyclic alcohols by ring-opening and cross-recombination between alkyl and N-oxyl radicals.

Radical ring-opening oxyimidation of cyclobutanols and cyclopropanols with the formation of ω-functionalized ketones was discovered. The oxidative C-O coupling proceeds via the interception of a primary alkyl radical generated from a cyclic alcohol with a reactive radical generated in situ, which is an electron-deficient N-oxyl radical. The developed conditions allow for the balanced generation rates of carbon- and N-oxyl radicals, which are necessary for their selective cross-recombination. Thus, typical competitive dimerization processes of carbon-centered radicals, their intermolecular cyclization, and N-oxyl radical self-decay are suppressed. The method is applicable to a wide range of cyclobutanols and results in oxyimidated ketones in yields of up to 82%.

VALIDATION OF CONTINUOUS FLOW METAL PLATE REACTORS IN THE TERPENE KETONE SYNTHESIS BY ALCOHOL OXIDATION

The present study elucidates the oxidation of alcohols to terpene ketones using dichloro(p-cymene) ruthenium (II) dimer catalyst by continuous flow process using a metal plate reactor. The synthesized products were separated and validated using GC, GCMS, 1H-NMR, and 13C-NMR techniques. The reaction process exhibited product yield in the range of 80-95% on a scale of 1-80 grams. Optimization studies were conducted to calibrate the reaction conditions to improve the product yield. The scope of the reaction was explored using aromatic, cyclic, and aliphatic alcohols under optimized conditions, which resulted in high yields of terpene ketones. A reaction mechanism is proposed for the oxidation of alcohols by a continuous flow process. The significant advantages of the current protocol include synthesis at mild conditions, safer handling of reagents, flexibility to tune reaction conditions, and straightforward scale-up in the range of 1- 80 grams with high efficiency and reproducibility.

Enhancing the ketonization ability of CeO2 for deoxygenation of biomass-derived sugars by Fe doping

Ketonization of oxygenated compounds in pyrolytic products of biomass is an effective means for deoxygenation and upgrading of bio-oils. However, the ketonization potential of biomass-derived sugars and the mechanism underneath remain unclear. On this basis, a series of Fe doped CeO2 catalysts were synthesized and employed for catalytic ketonization of xylan. Characterization of the catalysts proved the successful formation of the Fe-CeOx solid solution. Doping an appropriate amount of Fe (20–33%) ions on CeO2 could obviously increase the number of oxygen vacancy and basic sites by up to 56.31% and 29.6%, respectively. During the catalytic reaction of xylan, pure CeO2 exhibited a good ketonization ability during xylan pyrolysis, and the introduction of a certain amount of Fe further enhanced the ability. The highest yield of ketones was obtained by 33%Fe-CeO2, which was 38% higher than pure CeO2. The selectivity to linear ketones (acetone and 2-butanone) reached a maximum of 85% for 57%Fe-CeOx. Thus, oxygen-rich compounds had been converted to low oxygen containing and high-quality ketone components. Introducing Fe into CeO2 favored the production of ethylene glycol rather than 2,3-dihydroxy propanal, and thus promoted the yield of acetone. This investigation provides fundamentals for the deoxygenation of biomass through catalytic ketonization, aiming at the production of value-added ketone products.

A Sustainable Ruthenium(III) Chloride Catalyzed Alcohol Oxidation

AbstractSystematic optimization of the ruthenium‐catalyzed oxidation of alcohols with tert‐butyl hydroperoxide (TBHP) as the oxidizing agent was carried out. This resulted in the development of a sustainable protocol with a water/tert‐butanol mixture as the solvent and an optimum use of the oxidizing agent by continuous addition with a syringe pump. The protocol is applicable for a broad variety of substrates. High yields of ketones and aldehydes are accessible.

Homogeneous Iron‐Catalysed Oxidation Of Non‐Activated Alkanes With Hydrogen Peroxide

AbstractA novel synthetic protocol for the direct oxidation of alkanes, including cyclic and linear ones, to give ketones and alcohols using hydrogen peroxide as terminal oxidant under ambient conditions is presented. The active catalyst for this challenging transformation is conveniently generated by combination of simple Fe salts with N‐methyl bis(picolylamine) (Me‐bpa). Utilizing picolinic acid as additive leads to improved yields of ketones and alcohols (32‐57 %). The reaction can be conveniently scaled up to multi‐g scale.

Enhanced selective production of aldehydes and ketones by catalytic upgrading of pyrolysis vapor from holocellulose over red mud-based composite catalysts

This work proposes an effective method for the utilization of agricultural residues and red mud (RM) to produce the carbonyl platform compounds for the synthesis of high-value biofuels. The carbonyl platform compounds were synthesized by catalytic upgrading of pyrolysis vapor from holocellulose over RM composite catalyst. The maximized yield of aldehydes and ketones was obtained with the cellulose-to-hemicellulose mass ratio of 3:2, which was consistent with that of bagasse. Two types of RM were selected for the carbonylation of pyrolysis vapors, in which the type prepared by Bayer process containing more Fe2O3 exhibited better carbonylation performance. The ZrO2-loaded RM composite catalyst was prepared, and it was found that the yield of aldehydes and ketones was greatly boosted. Finally, RM composite catalysts supported by five individual metal oxide were prepared, the correlation between the oxidizability of catalyst and the aldehyde/ketone mole ratio was established, and it was revealed that the stronger oxidizability of the composite catalysts was usually accompanied with the decreased aldehydes/ketones mole ratio. Biomass and RM wastes were used as resources in this study, this waste-to-energy idea contributes to optimizing the utilization of waste and promoting the production of biofuels.

One-Pot Photocatalytic Cleavage of Lignin β–O–4 Models by Dehydrogenation–Hydrogenolysis

Valorizing lignin into valuable chemicals requires the selective breaking of a large number of C–O bonds found in the β–O–4 structure. In this study, we present a one-pot strategy that utilizes two NiO/TiO2 catalysts for the photocatalytic depolymerization of β–O–4 alcohols. The S-1.6%NiO/TiO2 catalyst is used for the dehydrogenation of β–O–4 alcohols at 450 nm. Then, the L-0.8%NiO/TiO2 catalyst is employed for the hydrogenolysis of β–O–4 ketones at 365 nm. Remarkably, the dehydrogenation–hydrogenolysis tandem reaction can be conducted in one pot, which affords high yields of ketones and phenols (up to 89%) from β–O–4 alcohols. Additionally, the L-0.8%NiO/TiO2 catalyst prepared in this article is the smallest NiO/TiO2 photocatalyst reported to date, and the size of NiO in the S-1.6%NiO/TiO2 catalyst is even small enough to enter the lattice of TiO2. We successfully regulated the reaction selectivity by controlling the loading method and the amount of NiO. Our work offers a promising solution for efficiently cleaving target bonds in lignin and provides insights into the design of efficient photocatalysts.

Solid-State Silver-Catalyzed Ring-Opening Fluorination of Cyclobutanols by Using Mechanochemistry

AbstractIn this report, we demonstrate that a ball-milling technique facilitates fast and efficient silver-catalyzed ring-opening fluorination of cyclobutanols. This is the first report of a catalytic C–C bond-cleavage/functionalization reaction under solid-state mechanochemical conditions. The developed protocol affords a high yield of γ-fluorinated ketones within much shorter reaction times, and requires less silver catalyst and Selectfluor compared with the previous solution-based conditions. Notably, the process can be carried out in air. Because of the reduced use of chemicals and the simple time-saving experimental procedures, this technique is an efficient and environmentally friendly way to access γ-fluorinated ketones.

Biomass catalytic pyrolysis over CaO microspheres: Relationship between the production of bio-oil components and CO2 capture

Biomass catalytic pyrolysis is a promising way for the clean and even “Carbon-Negative” utilization of biomass via the in-situ upgrading bio-oil and reducing the emissions of CO2. In this work, CaO microspheres (CaO-H) prepared via hydrothermal method were used to adsorb CO2 and catalyze the reforming of bio-oil in the pyrolysis process of rice straw (RS) simultaneously. The results showed that CaO-H had the more strong basic sites compared with commercial CaO and thus the better adsorption capacity of CO2 (∼0.5 g/g CaO) at 700 °C and the stronger effect on the generation of bio-oil components and CO2. And strong relationships presented between the formation of CO2 and the composition of bio-oil. The yield of phenols and ketones can be enhanced by 37.17% and 56.76% respectively via the addition of CaO-H at the pyrolysis temperature of 650 °C, companying with the decrease of CO2 yield by 35.13%. It is also inferred that the CO2 reforming of bio-oil and the insertion of CO in CO2 into bio-oil components was strengthened during the biomass pyrolysis over CaO-H especially at the temperature of 650 °C. The possible mechanism of biomass pyrolysis over CaO-H was also proposed.

Co-feeding enhances the yield of methyl ketones.

By combining computational and experimental work, we demonstrate that feeding ethanol in addition to glucose improves the yield of biotechnologically produced methyl ketones.

Electron-Deficient Fluoroarene-Mediated Synthesis of Trifluoromethyl Ketones from Carboxylic Acids.

Fluoroarene-mediated trifluoromethylation of carboxylic acids for the synthesis of trifluoromethyl ketones is disclosed. The fluoroarene activates the acid group and generates the fluoride source in situ for the trifluoromethylation reaction. The present protocol is safe and metal-free, operates under mild reaction conditions, and does not require any external additives to generate trifluoromethyl anion. The current transformation provides good functional group tolerance and also delivers 92% and 88% yields of trifluoromethyl ketones in batch and continuous flow, respectively.

Metal-free synthesis of α-acyloxy ketones from carboxylic acids and sulfoxonium ylides.

A straightforward, catalyst- and additive-free approach has been described for synthesizing α-acyloxy ketones from β-ketosulfoxonium ylides and carboxylic acids. Moderate to high yields of α-acyloxy ketones were produced using sulfoxonium ylides and carboxylic acids adorned with various functional groups. Eventually, the applicability of this approach has been shown via a large-scale reaction and transforming the synthesized α-acyloxy ketone derivatives into other valuable compounds.

How do crystal shapes of nano-ceria determine its ketonization performance during biomass pyrolysis?

Catalytic pyrolysis of biomass over CeO2 to prepare ketonic chemicals is an important way to achieve carbon emission reduction, whereas the role of catalyst structure has long been overlooked. In this work, nano-CeO2 with different crystal shapes, namely nanorods (R-CeO2), nano-polyhedra (P-CeO2), and nanocubes (C-CeO2), were synthesized and then tested in catalytic ketonization of xylan. Results showed that among all the three catalysts, C-CeO2 produced the highest yield of ketones. Characterization results revealed that C-CeO2 presented the lowest content of oxygen vacancies while exhibiting the highest proportion of {100} facets, proving that the {100} facets made a greater contribution to the total yield of ketones. On the other hand, P-CeO2 and R-CeO2 displayed a better selectivity to linear ketones, which was beneficial to improving the product quality. The relative contents of {111} facets of these catalysts were higher than C-CeO2, demonstrating that the {111} facets could selectively produce linear ketones. The proposed mechanism indicated that P-CeO2 and R-CeO2 principally enhanced the ketonic deoxygenation reactions, while C-CeO2 also promoted the recyclization reaction, producing more cyclic ketones. These findings disclose that the {111} facets of CeO2 are more favorable to producing valuable linear ketones.

Study of Cocoa Pod Husks Thermal Decomposition

Thermal decomposition of cocoa pod husks under inert and oxidizing atmospheres was studied. Samples from Cotopaxi, Ecuador were used as raw material. Thermogravimetry based experiments were used to obtain decomposition data vs. temperature. A novel strategy to fit the TG and DTG curves was used giving good fit by considering, in the kinetic model, four biomass fractions following independent reactions. Analytical pyrolysis was used to determine the composition of volatile compounds obtained in slow (150–350, 350–500 °C) and flash pyrolysis (400 °C). The results indicate that in the slow pyrolysis experiments at low temperatures (150–350 °C), the highest area percentages correspond to ketones (7.5%), organic acids (12.5%) and phenolic derivatives (10%), while at increased temperatures (350–500 °C) the higher percentages are clearly focused on phenolic derivatives (12%) and aromatic compounds (10%). Comparing the results of flash pyrolysis at 400 °C (i.e., higher heating rate but lower final temperature), an increase in the yield of ketones and organic acids is observed compared to slow pyrolysis, but the percentage of phenols and aromatics decreases. The results obtained allow deducing the operating conditions to maximize the mass fraction of the different functional groups identified.

Mechanistic insights on base-DMSO mediated aerobic oxidation of (hetero)benzylic C-H bonds

Aerobic oxidation of (hetero)benzylic C-H bonds to ketone products always relies on radical process initiated by transition-metal catalysis. Using inorganic bases, here we report an efficient transition-metal-free strategy, which is enabled by DMSO as both the high-polar solvent and the effective reductant. The ionic mechanism was suggested for this reaction, and a high yield of ketones was obtained by choosing the alkalinity-matched inorganic base with the acidity of (hetero)benzylic C-H bonds. Via kinetic experiments, a mixed mechanism with two reaction pathways was suggested for the generation of ketones, one of which involved the reduction of peroxide intermediates toward alcohols intermediates by DMSO, while the dehydration of peroxide intermediates lead to the direct formation of ketones in the other pathway. These findings not only provide a greener approach for ketones production from (hetero)benzylic oxidation, but also encourage the possible strategy to generate alcohols under inorganic base catalysis.

Copper(II) complexes supported by 8-hydroxyquinoline-imine ligands: Synthesis, characterization and catalysis in aerobic alcohols oxidation

Treatment of Cu(OAc)2·4H2O with 8-hydroxylquinoline-imine ligands [2-(ArN = HC)-8-OH]C9H5N (Ar = 2,6-iPr2C6H3, L1H; Ar = 4-ClC6H4, L2H; Ar = 4-BrC6H4, L3H and Ar = 4-OMeC6H4, L4H) in refluxing EtOH gave the dual-ligand coordinated copper complexes [L2Cu] 1a-1d in good yields, respectively. All the four Cu complexes were characterized by IR, EPR, elemental analysis and HR-MS. Furthermore, the molecular structures of complexes 1a and 1d were further confirmed by X-ray crystallographic analysis. These complexes displayed high catalytic activity and good selectivity for aerobic oxidation of primary and secondary alcohols in the presence of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl) as the co-catalyst. The yields of desired aldehydes are decent (up to 84%) and the corresponding yields of ketones are in the range of 78–91%.

Insight into the selective production of aldehydes and ketones by catalytic upgrading of biomass pyrolysis vapor over ZrO2:Cellulose and xylan

Catalytic upgrading of pyrolysis gas components from cellulose and xylan was investigated over ZrO2 catalyst to produce aldehydes and ketones. The oxygen content in the bio-oil was reduced by aldol condensation and hydrogenation of aldehydes and ketones. The optimal pyrolysis temperature of cellulose and xylan were determined to be 400 °C and 350 °C and the carbon yields of aldehydes and ketones reached 54.49% and 52.05% respectively. In order to explore the formation mechanism of aldehydes and ketones, the evolution of typical products by controlling the reaction time was studied. The catalytic pyrolysis was complete and the product content was maximum at 20 min H2O played a role in providing oxygen atoms and increasing ZrO2 reaction activity in the carbonylation process. The binding energy of the catalyst was calculated as −15.69 kcal/mol by density functional theory (DFT). It was found that the presence of water can remove the coke on the catalyst surface and increase the activity of ZrO2. The yield of aldehydes and ketones reached 58.17% and 55.85% of cellulose and xylan with the presence of 15 wt% H2O in the carbonylation process. According to the evolution of the above experimental products, the generation pathways of four main carbonylation products (acetone, methyl ethyl ketone, butyraldehyde and furfural) were proposed. Through this research, the effective utilization of biomass could be realized.