Synthesis Of Phenol Research Articles

Gold(I) Complexes with Eight‐Membered NHC Ligands: Synthesis, Structures and Catalytic Activity

AbstractA series of expanded‐ring NHC gold complexes of the formula (NaphtDHD−Ar)Au−X (NaphtDHD=4,5‐dihydro‐1H‐naphtho[1,8‐ef][1,3]diazocin‐3(2H)‐ylidene; Ar: Mes=2,4,6‐trimethylphenyl, Dipp=2,6‐diisopropylphenyl or Xyl=2,6‐dimethylphenyl; X=Cl, NCCH3, NTf2) have been synthesized, including the first gold(I) triflimidate complex (5) stabilized by an eight‐membered NHC ligand. The new organogold compounds have been characterized by mass spectrometry, IR spectroscopy, and 1H and 13C NMR spectroscopy. The structural geometries of 3 b–c and 5 have been unequivocally established by crystallographic analysis revealing broad N‐C‐N angles (>121°) and high buried volume values (46–54%). The first catalytic studies were carried out on the cycloisomerization of 1,6‐enynes, obtaining full conversions (0.5 mol% catalyst loading) and excellent endo/exo selectivity (up to 99:1), and on the gold‐catalyzed phenol synthesis. Lastly, the (NaphtDHD‐Dipp)Au+ NTf2− species was subjected to a kinetic experiment in the cyclization of a N‐propargyl carboxamide to evaluate the efficiency of the pre‐formed catalyst (5) and the in situ activated gold complex (3 b+AgNTf2).magnified image

Synthesis and thermal properties of phenol- and amine-capped main-chain benzoxazine oligomers with multiple methyl substitutions

A series of main-chain benzoxazine oligomers with different methyl substitutions are successfully synthesized. Chemical structures are analyzed by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and gel permeation chromatography. Effects of methyl substitutions on chemical shifts of protons in oxazine ring and thermal properties, including glass transition temperature, thermal stability, and char yield, are discussed. The influences of methyl substitutions on different positions are demonstrated: (i) substitution on phenols induces obvious increase in curing temperature while substitution on amine does not show apparent impact; (ii) substitution at different positions results in T g variation, following the sequence of none-substitution > substitution at end-capping > substitution on diamines in main-chain > substitution on bisphenols in main-chain; and (iii) substitution at end-capping would cause apparent deterioration in thermal stability while substitution on diamines in main-chain would benefit thermal stability and char yield. Experimental results and related explanations are provided in detail.

苯酚取代基4-氨基-1,2,4-三氮唑-3-硫醚的合成及其抑菌活性

苯酚取代基4-氨基-1,2,4-三氮唑-3-硫醚的合成及其抑菌活性

Direct Hydroxylation of Benzene to Phenol by Dielectric Barrier Discharge Plasma

Direct synthesis of phenol from benzene was realized using atmospheric dielectric barrier discharge (DBD) plasma. In the process, various experimental parameters such as irradiation time, electrode height, and discharge power were found to play crucial roles in determining the yield and selectivity of phenol. Also, serious carbonization phenomenon was observed at the surface of used electrode due to the extensive interaction between benzene and electrode, which greatly inhibited the hydroxylation of benzene to phenol. To resolve this issue, silica coated electrode was employed, and significant improvement of conversion efficiency was obtained. The yield of phenol as high as 19.5% could be obtained in the optimal condition, and its selectivity was 83.3% based on the analysis of gas chromatography-mass spectrometry.

Low-Temperature Reverse Water-Gas Shift Process and Transformation of Renewable Carbon Resources to Value-Added Chemicals.

The use of CO2 instead of toxic CO in the production of important chemicals has attracted widespread interest, and the reverse water-gas shift reaction (RWGSR) is the key step for this kind of processes. Although the thermodynamic limitations are overcome by the reaction of CO with other compounds, the temperature of most reactions involving RWGSR is usually very high owing to the inertness of CO2 . Herein, it was found that Ru3 (CO)12 could catalyze the RWGSR in the ionic liquid HMimBF4 without ligand or promoter, and CO could be produced at 80 °C, which was much lower than the temperatures reported to date. Detailed studies showed that the BF4 - in the ionic liquid played a crucial role in the low-temperature RWGSR. Based on the low-temperature RWGSR, three important routes to transform CO2 into valuable chemicals were developed, including synthesis of xanthone from CO2 and diaryl ethers, synthesis of phenol and acetic acid from CO2 and anisole, and production of acetic acid from CO2 and lignin. The reactions could occur at temperature as low as 80 °C, and low-temperature RWGSR was essential for the reactions under mild conditions. The strategy opens the way to produce value-added chemicals by using CO2 and H2 as feedstocks under low temperature.

Synthesis of Lignin-based Phenol Terminated Hyperbranched Polymer.

In this work, we proved the efficient synthesis of a bio-based hyper-branched polyphenol from a modified lignin degradation fragment. Protocatechuic acid was readily obtained from vanillin, a lignin degradation product, via alkaline conditions, and further polymerised to yield high molecular weight hyperbranched phenol terminated polyesters. Vanillic acid was also subjected to similar polymerisation conditions in order to compare polymerisation kinetics and differences between linear and hyperbranched polymers. Overall, protocatechuic acid was faster to polymerise and more thermostable with a degradation temperature well above linear vanillic acid polyester. Both polymers exhibited important radical scavenging activity (RSA) compared to commercial antioxidant and present tremendous potential for antioxidant applications.

Synthesis of Ethyl Phenol over Modified HZSM-5 Catalyst in a Fixed Bed Reactor

Abstract The selective synthesis of p-ethyl phenol in vapor phase alkylation of phenol with ethanol was investigated in a fixed bed flow reactor on cerium modified zeolite CeZSM5 at temperature 693 K. A series of cerium modified zeolite such as Ce4ZSM54, Ce6ZSM56, Ce8ZSM58, Ce10ZSM5 were prepared by modifying with 4 %, 6 %, 8 % and 10 % ceric ammonium nitrate solution respectively. HZSM-5 zeolite exchanged with 10 % cerium nitrate solution was proved to be the best of all the catalyst used. The modified catalyst was further characterized by SEM, XRD and EDS. Phenol reacted with ethanol to form ethylphenyl ether by O-alkylation, and p-ethylphenol- and o-ethylphenol isomers by C-alkylation; secondary products were m-ethylphenol and dialkylated compounds. Reactions were carried out in the temperature 623 K–693 K, reactant mole ratio 0.2–0.5 over modified HZSM-5 zeolite. The optimum operating condition for maximum selectivity of p-ethyl phenol were EtOH to phenol mole ratio, 4:1; temperature, 623 K; space-time, 10.2 kg h/kmol and 1 atm pressure. A detailed kinetic study was carried out for the ethyl phenol synthesis reaction. From the product distribution pattern, a kinetic model for the reactions was proposed following the Langmuir–Hinshelwood approach. The kinetic and adsorption parameters of the rate equation were determined by non-linear regression analysis. From the kinetic analysis of the experimental data, the apparent activation energy for the reaction was determined as 43.27 kJ/mol.

NH3 -Driven Benzene C-H Activation with O2 that Opens a New Way for Selective Phenol Synthesis.

Catalytic benzene C-H activation toward selective phenol synthesis with O2 remains a stimulating challenge to be tackled. Phenol is currently produced industrially by the three-steps cumene process in liquid phase, which is energy-intensive and not environmentally friendly. Hence, there is a strong demand for an alternative gas-phase single-path reaction process. This account documents the pivotal confined single metal ion site platform with a sufficiently large coordination sphere in β zeolite pores, which promotes the unprecedented catalysis for the selective benzene hydroxylation with O2 under coexisting NH3 by the new inter-ligand concerted mechanism. Among alkali and alkaline-earth metal ions and transition and precious metal ions, single Cs+ and Rb+ sites with ion diameters >0.300 nm in the β pores exhibited good performances for the direct phenol synthesis in a gas-phase single-path reaction process. The single Cs+ and Rb+ sites that possess neither significant Lewis acidic-basic property nor redox property, cannot activate benzene, O2 , and NH3 , respectively, whereas when they coadsorbed together, the reaction of the inter-coadsorbates on the single alkali-metal ion site proceeds concertedly (the inter-ligand concerted mechanism), bringing about the benzene C-H activation toward phenol synthesis. The NH3 -driven benzene C-H activation with O2 was compared to the switchover of the reaction pathways from the deep oxidation to selective oxidation of benzene by coexisting NH3 on Pt6 metallic cluster/β and Ni4 O4 oxide cluster/β. The NH3 -driven selective oxidation mechanism observed with the Cs+ /β and Rb+ /β differs from the traditional redox catalysis (Mars-van Krevelen) mechanism, simple Langmuir-Hinshelwood mechanism, and acid-base catalysis mechanism involving clearly defined interaction modes. The present catalysis concept opens a new way for catalytic selective oxidation processes involving direct phenol synthesis.

Advances in the one step catalytic synthesis of phenol

Advances in the one step catalytic synthesis of phenol

Differential responses of walnut cultivars to cold storage and their correlation with postharvest physiological parameters

In this study, we screened eight walnut (Juglans regia L.) cultivars (‘Xifu2’, ‘Shaanhe’, ‘Weina’, ‘Xiangling’, ‘Xiluo3’, ‘Xifu1’, ‘Liaoning4’, and ‘Qingxiang’) in order to establish reliable selection criteria for storage-tolerance. Fresh walnut fruit were stored at 0 ± 0.5 °C and 70–80% relative humidity. Browning index, postharvest physio-biochemical characteristics, acid value, and sensory quality were measured. The results showed that ‘Xifu2’, ‘Shaanhe’, and ‘Weina’ developed browning early and quickly and storage was terminated for these cultivars at 60 days. ‘Xiluo3’, ‘Xifu1’, ‘Liaoning4’, and ‘Qingxiang’ had a slow browning rate and storage was terminated at 72 days. ‘Xiangling’ developed browning at a medium rate and storage was terminated at 72 days. Correlation analysis suggested that the terminal browning index of each cultivar positively correlated with lipoxygenase activity at 18 days of storage, polyphenol oxidase activity at 18–30 days, malondialdehyde content at 18 days, and the respiration rate at 42 days, while it negatively correlated with the total phenolic content at 18 days and phenylalanine ammonia lyase activity at 12 days. The storage tolerance of each cultivar was evaluated according to the terminal browning index, acid value, and sensory quality. Comprehensive evaluation and cluster analysis were performed to rank the cold storage tolerance of the eight cultivars as follows: ‘Qingxiang’ and ‘Xifu1’ > ‘Liaoning4’ and ‘Xiluo3’ > ‘Xifu2’ and ‘Xiangling’ > ‘Shaanhe’ and ‘Weina’. In conclusion, cultivars used for fresh in-husk walnut fruit with lower levels of membrane peroxidation and phenol oxidation, and higher level of phenol synthesis around 18 days of storage would be suitable candidates for cold storage. ‘Qingxiang’ and ‘Xifu1’ were selected as storage-tolerant cultivars.

Gut microbiome-derived phenyl sulfate contributes to albuminuria in diabetic kidney disease

Diabetic kidney disease is a major cause of renal failure that urgently necessitates a breakthrough in disease management. Here we show using untargeted metabolomics that levels of phenyl sulfate, a gut microbiota-derived metabolite, increase with the progression of diabetes in rats overexpressing human uremic toxin transporter SLCO4C1 in the kidney, and are decreased in rats with limited proteinuria. In experimental models of diabetes, phenyl sulfate administration induces albuminuria and podocyte damage. In a diabetic patient cohort, phenyl sulfate levels significantly correlate with basal and predicted 2-year progression of albuminuria in patients with microalbuminuria. Inhibition of tyrosine phenol-lyase, a bacterial enzyme responsible for the synthesis of phenol from dietary tyrosine before it is metabolized into phenyl sulfate in the liver, reduces albuminuria in diabetic mice. Together, our results suggest that phenyl sulfate contributes to albuminuria and could be used as a disease marker and future therapeutic target in diabetic kidney disease.

Overview of Photocatalytic Membrane Reactors in Organic Synthesis, Energy Storage and Environmental Applications

This paper presents an overview of recent reports on photocatalytic membrane reactors (PMRs) in organic synthesis as well as water and wastewater treatment. A brief introduction to slurry PMRs and the systems equipped with photocatalytic membranes (PMs) is given. The methods of PM production are also presented. Moreover, the process parameters affecting the performance of PMRs are characterized. The applications of PMRs in organic synthesis are discussed, including photocatalytic conversion of CO2, synthesis of KA oil by photocatalytic oxidation, conversion of acetophenone to phenylethanol, synthesis of vanillin and phenol, as well as hydrogen production. Furthermore, the configurations and applications of PMRs for removal of organic contaminants from model solutions, natural water and municipal or industrial wastewater are described. It was concluded that PMRs represent a promising green technology; however, before the application in industry, additional studies are still required. These should be aimed at improvement of process efficiency, mainly by development and application of visible light active photocatalysts and novel membranes resistant to the harsh conditions prevailing in these systems.

Synthesis of Benzyl Phenol from Benzyl Aryl Ether by Polyphosphoric Acid-Catalyzed Benzyl Rearrangement

Synthesis of Benzyl Phenol from Benzyl Aryl Ether by Polyphosphoric Acid-Catalyzed Benzyl Rearrangement

Copper-catalyzed synthesis of phenol and diaryl ether derivatives via hydroxylation of diaryliodoniums.

A copper-catalysed hydroxylation of diaryliodoniums to generate phenols and diaryl ethers is reported. This method allows the synthesis of diversely functionalized phenols under mild reaction conditions without the need for a strong inorganic base or an expensive noble-metal catalyst. Significantly, convenient application of diaryliodoniums is demonstrated in the preparation of diaryl ethers in a one-pot operation.

One step phenol synthesis from benzene catalysed by nickel(ii) complexes

Nickel(ii)complexes of N4-ligands are reported as efficient catalysts for direct benzene hydroxylationviabis(μ-oxo)dinickel(iii) intermediate species. The exclusive phenol formation is achieved with a yield of 41%.

Telescoped Sequence of Exothermic and Endothermic Reactions in Multistep Flow Synthesis

A multistep sequential flow synthesis of isopropyl phenol is demonstrated, involving 4-step exothermic, endothermic, and temperature sensitive reactions such as nitration, reduction, diazotization, and high temperature hydrolysis. Nitration of cumene with fuming nitric acid produces 2- and 4-nitrocumene which are converted into respective cumidines by the hydrogenation using Pd/Ni catalyst in H-cube with gravity separation. Hydrolysis of in situ generated diazonium salts in the boiling acidic conditions is carried out using integration of flow and microwave-assisted synthesis. 58% of 4-isopropyl phenol was obtained. The sequential flow synthesis can be applied to synthesize other organic compounds involving this specific sequence of reactions.

Biochemical tolerance of Suaeda maritima L. (Dumort) as a potential species for phytoextracting heavy metal and salt in paper mill effluent contaminated soil.

Suaeda maritima is a halophyte that has been evolutionary adapted to cope with saline and heavy metal conditions. The aim of the present study was to examine the biochemical response of Suaeda maritima against phytoextracting heavy metals and salts from paper mill effluent. Suaeda maritima seedlings have been grown for 120 days with an irrigation solution of 250 ml of 75% raw paper mill effluent after four drenching. Analysis of biochemical parameters revealed that maximum synthesis of chlorophyll, protein, phenol, proline and glycinebetaine may be involved in their ability to cope with heavy metal and salt stress. The present study confirms that the accumulation and increase of biochemical constituents can be considered as an efficient ROS scavenger and also maintain cellular homeostasis and metabolic functions in photosynthetically active leaves in Suaeda maritima, during phytoextraction studies.
 Keywords: phytoextraction, paper mill effluent, Suaeda maritima, biochemical, heavy metal and salts

Brettanomyces anomalus, a double drawback for cider aroma

Sixty-six French ciders were collected and characterized to build up a data base of eighty-eight variables, including sensory descriptors, aroma description and physicochemical variables. A classification in four main sensory categories was made on the basis of sensorial data. Fruity-Floral ciders were rich in acetate esters and low in volatile phenols, in opposition with phenol-like or off-flavour ciders having an inverse ratio. In order to explain this observation, an essential result was the demonstration of Brettanomyces anomalus implication, not only in volatile phenol synthesis, but also in acetate ester degradation. Brettanomyces anomalus exhibited an intracellular acetyl esterase activity. At last, both mechanisms, acetate ester degradation and phenol synthesis, contribute to the decrease of cider fruitiness.

Smoke from simulated forest fire alters secondary metabolites in Vitis vinifera L. berries and wine.

The exposure of Vitis vinifera L. berries to forest fire smoke changes the concentration of phenylpropanoid metabolites in berries and the resulting wine. The exposure of Vitis vinifera L. berries (i.e., wine grapes) to forest fire smoke can lead to a wine defect known as smoke taint that is characterized by unpleasant "smoky" and "ashy" aromas and flavors. The intensity of smoke taint is associated with the concentration of organoleptic volatile phenols that are produced during the combustion-mediated oxidation of lignocellulosic biomass and subsequently concentrated in berries prior to fermentation. However, these same smoke-derived volatile phenols are also produced via metabolic pathways endogenous to berries. It follows then that an influx of exogenous volatile phenols (i.e., from forest fire smoke) could alter endogenous metabolism associated with volatile phenol synthesis, which occurs via the shikimic acid/phenylpropanoid pathways. The presence of ozone and karrikins in forest fire smoke, as well as changes to stomatal conductance that can occur from exposure to forest fire smoke also have the potential to influence phenylpropanoid metabolism. This study demonstrated changes in phenylpropanoid metabolites in Pinot noir berries and wine from three vineyards following the exposure of Vitis viniferaL. vines to simulated forest fire smoke. This included changes to metabolites associated with mouth feel and color in wine, both of which are important sensorial qualities to wine producers and consumers. The results reported are critical to understanding the chemical changes associated with smoke taint beyond volatile phenols, which in turn, may aid the development of preventative and remedial strategies.

Process intensification on the selective catalytic oxidation of cumene with ionic liquids

The cumene-phenol process, based on the decomposition of cumene hydroperoxide (CHP) to phenol and acetone, is currently used worldwide for phenol synthesis. Peroxidation of cumene is the key step to synthesis of phenol. Alkali solutions, such as NaOH, were added to the oxidation system traditionally. In this paper, a novel type of catalyst, ionic liquids (ILs), for the cumene oxidation was proposed to intensify the catalytic oxidation of cumene. The reaction rate was much faster in the presence of ILs than that of NaOH. The structure and constitute of the ILs influenced the conversion of cumene and the selectivity of CHP. For the imidazolium-based ILs, the selectivity of CHP under the catalysis of [C4dmim]Br (53.1%) was higher than that of [C4mim]Br (36.2%). However, the selectivity in the presence of [C4mim]OH (67.1%) was almost as the same as that of [C4dmim]OH (63.2%). It was found that the acidic proton of the imidazolium ring catalyzed the decomposition of CHP. This was proved by that the ILs with less acidic protons exhibited better selectivity of CHP. The selectivity of CHP with [MP4]Br as catalyst reached 87.7%.