Synthesis Of Phenols Research Articles

Formal Transformation of Benzylic Carboxylic Acids to Phenols.

Phenols play a crucial role as core structural motifs in natural products and also serve as fundamental building blocks in synthetic chemistry. Apart from the known protocols for the conversion of aryl precursors to phenols (i.e., decarboxylative oxygenation), we report here the efficient synthesis of phenols from the stable and readily available benzylic carboxylic acids under mild reaction conditions. The photocatalytic conversion of carboxylic acids to peroxides is a crucial step in this strategy, allowing the subsequent C-O bond formation via Hock rearrangement.

Sustainable green synthesis of magnetically recoverable cobalt ferrite nanoparticles for the facile synthesis of nitroarenes and phenols

Arylboronic acids can be converted to useful industrial and pharmaceutical molecular scaffolds like nitroaromatics and phenols. Nitroarenes are tremendously valuable organic compounds with an extensive history of existence in pharmaceuticals, explosives and as well as agrochemicals, indispensable intermediates to a wide range of chemicals. For this purpose, a ferromagnetic nanomaterial, CoFe2O4 is designed using different parts of Dillenia indica fruit extract. As synthesized nanoparticles (NPs) are employed for the very first time as an active catalyst for the facile ipso-nitration as well as ipso-hydroxylation of arylboronic acids for the cheaper, chemo-selective and efficient access of nitroarenes and phenols respectively and the catalytic system is highly sustainable for a great number of substrates with a high yield of product. The physio-chemical characteristics of the catalysts were established by FE-SEM, EDAX, Elemental mapping, PXRD, TEM, XPS,VSM.The catalyst is well-recoverable and reusable up-to five catalytic cycles without significant loss of its activity.

Cyclic variable temperature conditioning-maintained storage quality of sweet potatoes by enhancing antioxidant activity

The study investigated the effect of cyclic variable temperature conditioning (CVTC) on the quality parameters of sweet potatoes and their relationship with the antioxidant system (phenols synthesis and reactive oxygen species metabolism). Results showed that CVTC maintained the color and normal respiratory intensity of sweet potatoes and reduced the accumulation of malondialdehyde (MDA) during storage. In detail, total phenols content (TPC) and total flavonoids content (TFC) in CVTC group were significantly higher than those in control (CK), cold storage (CS), and high temperature conditioning (HTC) groups at 8 d, with increases of 17.58% and 85.12% from day 0, respectively. Additionally, phenylalanine ammonia lyase (PAL) and hydroxycinnamoyl transferase (HCT) activities in CVTC group were significantly higher than those in CK, CS, and HTC groups at 8 d. These results showed that CVTC activated the synthesis of phenols by activating the key enzymes activities, resulting in a significant increase in total phenols and flavonoids contents. Besides, CVTC improved the superoxide anion scavenging capacity of sweet potatoes and promoted the decomposition of hydrogen peroxide (H2O2). Meanwhile, superoxide dismutase (SOD) and catalase (CAT) activities in CVTC group were significantly higher than those in CK, CS, and HTC groups in the late storage period. In conclusion, CVTC enhanced the antioxidant activity of sweet potatoes by regulating the phenols synthesis and reactive oxygen species metabolism to maintain their postharvest quality.

Dehydrative Alkylation of Phenols with Alcohols via Formation of Triflate.

An efficient synergistic trityl cation ([Ph3C][B(C6F5)4])/triflic anhydride (Tf2O) catalyzed alkylation of phenols with alcohols is reported. Benefiting from the formation of the triflate in situ, cheap and readily available active alcohols can be used as the alkylating reagents, and the reaction proceeds under mild reaction conditions with a broad substrate scope. This protocol enables the synthesis of ortho-selective phenols and 2,4,6-trisubstitued phenols containing three different alkyl groups. tert-Amyl triflate was synthesized, and mechanistic studies support a triflate-mediated alkylation process.

Response of lignin and flavonoid metabolic pathways in Capsicum annuum to drought and waterlogging stresses

Water stress is a critical factor limiting the growth and development of Capsicum annuum. Flavonoids and lignin are important secondary metabolites that serve as signaling molecules in plant stress responses. However, the effects and regulatory mechanisms of lignin and flavonoids under water stress in Capsicum annuum remain unknown. The present study focused on the effects of drought and waterlogging stress on the morphology, hydrogen peroxide, and relative chlorophyll (SPAD), as well as enzyme activities, metabolite contents, and gene expression related to lignin and flavonoid metabolic pathways in Capsicum annuum. The results showed that drought and waterlogging stresses on the Capsicum annuum variety ‘Shuyu2’ significantly reduced plant height, stem thickness, and single-fruit weight, and increased fruit shape coefficients. Drought stress increased H2O2 and SPAD content, enhanced the activity levels of metabolic enzymes (phenylalanine deaminase, cinnamate 4-hydroxylase, coenzyme A ligase, peroxidase, and polyphenol oxidase), and up-regulated the expression of related genes, phenylalanine deaminase (PAL), trans-cinnamate monooxygenase (C4H), chalcone isomerase (CHI), and mangiferyl hydroxycinnamoyltransferase (HCT), while also promoting the accumulation of metabolites (total phenolics, flavonoids, and lignin) that have a restorative effect on drought stress. The continuous accumulation of H2O2 and the increase and then decrease in SPAD under waterlogging stress was also observed. Waterlogging stress also enhanced the activities of the above-mentioned metabolic enzymes, but the related genes were selectively down-regulated, e.g., C4H, 4CL, and peroxidase (POD), which resulted in the inhibition of the synthesis of lignin, flavonoids, and total phenols. These results indicate that the Capsicum annuum variety ‘Shuyu2’ is a drought-tolerant, waterlogging-sensitive variety. Meanwhile, the lignin and flavonoid pathway is a key pathway in response to drought stress in Capsicum annuum, which improves the theory of stress tolerance breeding in Capsicum annuum.

Copper-Catalyzed Synthesis of Phenols and Anilines

Copper-Catalyzed Synthesis of Phenols and Anilines

Sulphonic Acid Functionalized Ionic Liquids as an Efficient Catalyst for the Synthesis of Digeranyl Ethers and Geranyl Phenols

AbstractAn alternate synthetic approach was developed for the synthesis of the digeranyl ether and naturally occurring biologically active geranyl phenols using −SO3H functionalized ionic liquids within 0.5–1.5 h with better yields. This approach was further explored for different naturally occurring activated phenols with geraniol yielding geranyl phenols via alkylation at ambient temperature using ionic liquids as catalyst. The synthesized ionic liquids were characterized using Py‐IR studies to establish the Brønsted acidity and the Hammett acidity characteristics of all the four ionic liquids. Amongst these ionic liquids IL‐1 exhibited beneficial catalytic activity towards the synthesis of digeranyl ether and geranyl phenols with excellent yields. Reusability studies indicated that IL‐1 was recycled for seven times without losing the catalytic activity which was further corroborated with pre‐ and post‐characterization of IL‐1. This work also highlights the alternate route for the synthesis of the cannabinoid compounds and their analogues.

Synthesis of meta-carbonyl phenols and anilines

Phenols and anilines are of extreme importance for medicinal chemistry and material science. The development of efficient approaches to prepare both compounds has thus long been a vital research topic. The utility of phenols and anilines directly reflects the identity and pattern of substituents on the benzenoid ring. Electrophilic substitutions remain among the most powerful synthetic methods to substituted phenols and anilines, yet in principle achieving ortho- and para-substituted products. Therefore, the selective preparation of meta-substituted phenols and anilines is the most significant challenge. We herein report an efficient copper-catalyzed dehydrogenation strategy to exclusively synthesize meta-carbonyl phenols and anilines from carbonyl substituted cyclohexanes. Mechanistic studies indicate that this transformation undergoes a copper-catalyzed dehydrogenation/allylic hydroxylation or amination/oxidative dehydrogenation/aromatization cascade process.

Mechanism of Nitrous Oxide Activation in C(sp2)-O Bond Formation Reactions Catalyzed by Nickel Complexes.

Recent groundbreaking experimental reports demonstrated that Ni complexes bearing a bidentate- or tridentate-bipyridine-based ligand can be used to activate N2O for use as an O-transfer agent in C(sp2)-O bond formation reactions under mild experimental conditions. In this work, quantum chemical calculations are used to shed light on the mechanism through which such metal complexes catalytically activate nitrous oxide, providing new fundamental insights into the development of novel catalysts for N2O revalorization. As a case study, we consider the recent work by Cornella and co-workers (Nature, 2022, 604, 677) concerning the synthesis of phenols from aryl halides at room temperature, which requires the use of an external reducing agent. Our results suggest that the metal center remains in its Ni(II) oxidation state throughout the whole catalytic cycle, despite the presence of various redox steps in the mechanism and the Ni ability to maneuver between a number of oxidation states. This counterintuitive behavior is made possible by the ligand redox activity in the catalytic process, which involves accepting electrons from the reducing agent. Several possible pathways are systematically investigated, each associated with distinct activation modes, kinetics, and reaction outcomes. The governing factors in dictating the preferred path lie in the electronic nature of the ligand (strong vs weak field) and its geometric structure (specifically, the number of coordinating arms). These characteristics play a pivotal role in determining whether the process follows a catalytic or stoichiometric route and can be in principle modulated for the design of new metal complexes with tailored redox properties and reactivity.

Spatio-temporal variation in synthesis of some nutraceutical components of thorowax foldwing (Dicliptera bupleuroides Nees)

The present research was carried out to determine the spatiotemporal variation in accumulation of different nutritional and medicinal components in Dicliptera bupleuroides from the Soone valley in the Salt Range of Punjab, Pakistan. Most of the biochemical attributes were higher in the spring season than those in the other seasons; this might have been due to high soil pH during spring. High amounts of minerals and high pH are necessary for the synthesis of alkaloids, phenols, flavonoids, and fibers. Proteins, N, dry matter, fats and nitrogen free extract (NFE) were higher in summer, which might have been due to considerable availability of macro-nutrients during this season due to high moisture content because of high rainfall during the season. Spatial variation showed that phenols and flavonoids were associated with the population from Khabeki site (despite enough minerals and moisture availability) which might have been due to physical injuries caused by grazing and cutting. Minerals, proteins and N were also associated with the Khabeki population probably due to large amounts of minerals and moisture retention in the soil of the site and prevalent optimum environmental conditions therein. Alkaloids, fats, moisture and some minerals were associated with Anga and Knotti Garden sites which might have been due to high pH and prolonged salt stressed conditions at both sites.

Application of Bacillus tequilensis for the control of gray mold caused by Botrytis cinerea in blueberry and mechanisms of action: inducing phenylpropanoid pathway metabolism.

Botrytis cinerea a blueberry gray mold, is one of the main diseases affecting postharvest storage, causing significant losses. Several studies have shown that Bacillus tequilensis can prevent the growth of plant pathogens by producing various antibacterial substances, and can induce plant resistance. However, research on the biological management of post-harvest gray mold in blueberries using B. tequilensis remains unclear. To better control the postharvest gray mold of blueberry, the effects of B. tequilensis KXF6501 fermentation solution (YY) and KXF6501 cell-free supernatant (SQ) on the induction of disease resistance in blueberry fruits were studied using biochemical and transcriptomic analyses. We found that YY controlled the conidial germination and mycelial growth of B. cinerea in vitro, followed by SQ. After 3 d of culture, the lesion diameter and incidence of gray mold in blueberry fruits inoculated with YY and SQ were smaller than those in the control group. Therefore, gray mold in blueberries was effectively controlled during the prevention period, and the control effect of YY was better than that of SQ. Transcription spectrum analysis of blueberry peel tissue showed that the YY- and SQ-induced phenylpropane metabolic pathways had more differentially expressed genes (DEGs) than other biological pathways. In addition, biochemical analyses showed that YY treatment effectively enhanced the activity of enzymes related to the phenylpropane pathway (phenylalanine ammonialyase [PAL], cinnamate 4-hydroxylase [C4H], 4-coumarate CoA ligase [4CL], and polyphenol oxidase [PPO]) and stimulated the synthesis of lignin, total phenols, and flavonoids, followed by SQ. Compared with the control, the YY and SQ treatments reduced the weight loss rate and better maintained the appearance and nutritional quality of the blueberry fruits. Our findings suggest that B. tequilensis KXF6501 is potentially useful as a suitable bio-control agent in harvested blueberries.

CCC-NHC Au(iii) pincer complexes as a reliable platform for isolating elusive species.

The reactivity of unprecedented CCC-NHC Au(iii) pincer complexes has been investigated, employing a novel methodology for their preparation. Notably, this marks the inaugural case of CCC-NHC Au(iii) pincer complexes with a central aryl moiety where the two arms of the pincer ligand consist of N-heterocyclic carbenes (NHC). The stability conferred by the CCC-NHC ligand facilitated the isolation of elusive Au(iii) species, encompassing Au(iii)-formate, Au(iii)-F, Au(iii)-Me, and Au(iii)-alkynyl. Our study also unveiled the elusive Au(iii)-H species, offering valuable insights into its formation, stability, and reactivity. While the CCC-NHC Au(iii)-H complex remains stable at room temperature, its decomposition becomes conspicuous at elevated temperatures (>60 °C), exhibiting a more pronounced tendency under acidic conditions compared to basic ones. Through comprehensive experiments, we indirectly demonstrated the potential of Au(iii)-formate to undergo β-hydride elimination, becoming a key step in the dehydrogenation of formic acid. Theoretical calculations revealed variations in the reactivity of Au(iii)-H species towards sodium hydride and formic acid, highlighting a link between σ-donation from the pincer ligand and reaction energetics. Pincers with lower electron donation favored the reaction with sodium hydride but impeded the reaction with formic acid, whereas those with higher electron donation exhibited the opposite behavior. Additionally, the CCC-NHC Au(iii) pincer complex exhibited Lewis acid behavior, catalyzing the synthesis of phenols. In summary, the CCC-NHC Au(iii) pincer complex emerges as a versatile platform for isolating reactive species and unraveling elementary catalytic steps.

A Facile and General Oxidative Hydroxylation of Organoboron Compounds: Citric Acid as an Efficient Catalyst in Water to Access Phenolic and Alcoholic Motifs

An efficient and convenient method for the synthesis of phenols and aliphatic alcohols is described in this paper. The oxidative hydroxylation reaction of various organoboron compounds proceeded smoothly by employing H2O2 as the oxidant and citric acid as the catalyst in water at room temperature to produce phenols and aliphatic alcohols in satisfactory to excellent yields (up to 99% yield). Various synthetically useful functional groups, such as halogen atom, cyano, and nitro groups, remain intact during the oxidative hydroxylation. The developed catalytic system also could accommodate phenylboronic pinacol ester and potassium phenyltrifluoroborate to give the target product good yields.

Changes of the antioxidant system in pear (Pyrus communis L.) fruits by foliar application of copper, selenium, iron, and zinc nanoparticles

Innovations in agricultural nanotechnology are a viable option for improving the antioxidant system in the pear crop helping to mitigate the different types of abiotic and biotic stresses whose effects have increased due to the advance of climate change. Therefore, foliar applications were made with nanoparticles (NPs) of copper (Cu), iron (Fe), and zinc (Zn) at 250 ppm, as well as applications with selenium (Se) at 50 ppm, and control with water in a commercial pear orchard (Bartlett variety), to evaluate its effect on the behavior of the enzymatic antioxidant system, the concentration of bioactive compounds, and the evaluation of damage by lipid peroxidation, hydrogen peroxide concentration, and activity of polyphenol oxidases (PPO) in the fruits. The results indicate that the Cu and Se NPs stimulated in the fruits a greater synthesis of total phenols, flavonoids, and ascorbic acid, achieving higher concentrations than the control fruits, and also exhibited greater antioxidant activity in vitro. An opposite effect was observed in the fruits of the treatment with Zn NPs, since the concentration of phenols and flavonoids was reduced by 33.14 and 34.24 %, respectively, as well as a decrease in antioxidant activity. On the other hand, the Cu and Fe NPs improved the activity of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase, additionally, the integrity of the membranes was maintained, thus avoiding enzymatic browning due to the activity of the PPOs in the fruits. The highest concentration of malondialdehyde and PPOs activity was observed in the fruits of the treatment with Se and Zn NPs. The results indicate that the application of Cu NPs at 250 ppm can improve the enzymatic and non-enzymatic antioxidant system in Bartlett cultivar pear fruits.

Pre and postharvest spraying of arginine enhanced the stress resistance and promoted wound healing in broccoli during storage

Broccoli rapidly yellows and dehydrates post-harvest, causing a short storage life. Although arginine post-harvest has been shown to enhance broccoli’s storage quality and shelf life, it remains unclear whether pre-harvest treatment yields similar benefits. The results showed that pre-harvest spraying of 5 mM arginine reduces the respiration rate and delays electrolyte leakage during broccoli’s storage period, minimizing weight loss and yellowing and chlorophyll degradation. It also inhibits the degradation of ascorbic acid (ASA) and promotes the synthesis of total phenols, thereby increasing the total antioxidant capacity. Further studies showed that pre-harvest arginine spraying enhanced the activity of arginine decarboxylase (ADC), ornithine decarboxylase (ODC), and nitric oxide synthase (NOS). This accelerated the nitric oxide (NO) and the polyamine (PA) accumulation. Additionally, arginine aids in reactive oxygen species (ROS) balance and wound healing. Notably, pre-harvest arginine spraying was found to inhibit the hydrogen peroxide (H2O2) accumulation and enhance the activities of superoxide dismutase (SOD) and catalase (CAT), while also activating the phenylalanine ammonia lyase (PAL) and cinnamic acid 4-hydroxylase (C4H) activities. In conclusion, pre-harvest arginine spraying extends the broccoli’s storage life and improves its storage quality by promoting endogenous arginine catabolism, ROS metabolism, and the wounds healing. Therefore, this study establishes a theoretical foundation for pre-harvest handling in post-harvest broccoli storage.

Dehydrogenation of Cyclohexanones to Phenols: A Mini Review.

Phenol and its derivatives are important intermediates in the chemical industry, especially the pharmaceutical and electronic industries. The synthesis of phenols has attracted the attention of scientists due to their importance. Dehydrogenation of cyclohexanones is one of the promising aromatization strategies for phenols manufacture because the raw materials are low cost and stable. In recent years, some efficient and green methods with the use of H2, O2 and air, alkene, H2 and O2-free are described. This mini-review will summarize some recent developments relating to the dehydrogenation of cyclohexanones to phenols, along with their interesting mechanism aspects. The challenges and future trends of the transformation will be prospected. The synthesis of phenols from the dehydrogenation of cyclohexanones has recently attracted much attention. Some synthetic methods have been established, and interesting mechanisms have been proposed in some cases. Lots of catalysts were developed for the transformation to afford the corresponding product. Although the present methods still have drawbacks and limitations, it is supposed that many novel methods would probably be developed in the near future.

Arylazopyrazole linked Schiff bases as organocatalysts for the ipso-hydroxylation of arylboronic acids for the synthesis of phenols

A simple metal-free strategy for the synthesis of phenols from aryl and hetero aryl-boronic acids using arylazopyrazole linked o-hydroxyl Schiff base has been illustrated. These sustainable ipso-hydroxylations have very short reaction times, using aqueous H2O2 as the oxidant in aqueous-alcoholic medium. The current protocol has been demonstrated to be effective with a variety of electron-rich and electron-deficient aromatic substrates and provides access to a wide range of phenols. This is the first time that an azoyrazole linked Schiff base has been used to increase the nucleophilicity of H2O2, in oxidative hydroxylation reactions.

Core-Labeling (Radio) Synthesis of Phenols.

We report a method that enables the fast incorporation of carbon isotopes into the ipso carbon of phenols. Our approach relies on the synthesis of a 1,5-dibromo-1,4-pentadiene precursor, which upon lithium-halogen exchange followed by treatment with carbonate esters results in a formal [5 + 1] cyclization to form the phenol product. Using this strategy, we have prepared 12 1-13C-labeled phenols, show proof-of-concept for the labeling of phenols with carbon-14, and demonstrate phenol synthesis directly from cyclotron-produced [11C]CO2.

Lipase as Biocatalyst- for Synthesis of Phenol by Using Box–Behnken Design

This work highlighted the proficient and naturally safe methodology for the phenol synthesis using biocatalyst lipase. The development of sustainable synthetic protocol for various organic transformations is an important area of research attracts researchers to avoid use of volatile and hazardous organic solvents in reaction for greener and eco-friendly protocols. Lipase is subclass of esterase enzymes and acts as biocatalyst with industrial significance. They carry out biochemical transformation in non-aqueous and aqueous phases quickly. To further make the process more specific Design Expert software was used for the optimization of synthesize phenol for maximum % Yield and % Purity. Effect of temperature, Concentration of Catalyst, and Volume of Water was selected as an independent factor to get the maximum % Yield and % Purity of the phenol. The results confirmed the mathematical model robustness and justify experimental design. Therefore, the current protocol for synthesis of phenols from phenylboronic acid is greenest and environmentally benign alternative. The current convention has many benefits, like phenomenal product yields, reduced time of reaction, simple procedure to work up, and extensive substrate scope, cost-effective and also lipase was recuperated and reused multiple times without significant loss of its catalytic activity.

One-pot synthesis of trisubstituted 2-pyrones and polysubstituted phenols through Zn catalyzed cascade of ynone/condensation/elimination reactions

An efficient multicomponent method is described for the synthesis of a variety of trisubstituted 2-pyrones and polysubstituted phenols based on the Zn-catalyzed cascade reactions between ynone compounds and active methylene group containing diesters. The synthesis of titled compounds were achieved using Zn-catalyzed ynone synthesis followed by Knoevenagel condensation and elimination. Further, this methodology is applied to accomplish the synthesis of poylsubstuited phenols. HIGHLIGHTS Palladium and Ligand Free Zinc catalyzed One-Pot Synthesis of tri substituted 2-Pyrones and polysubstituted phenols. Economically liable method to synthesize the tri substituted 2-Pyrones and polysubstituted phenols products. Broad substrate scope. Synthesis of various tri substituted 2-Pyrones and polysubstituted phenols.