Ketone Structure Research Articles

How to Start a Total Synthesis from the Wieland-Miescher Ketone?

The Wieland-Miescher ketone consists of a couple of enantiomers of 9-methyl- Δ5(10)-octalin-1,6-dione, in which the configuration at 9-position is S- or R-type. The Robinson annulation of 2-methyl-1,3-cyclohexanedione with methyl vinyl ketone is able to afford the Wieland-Miescher ketone. As widely used in the total synthesis, the Wieland-Miescher ketone is treated at the beginning of total synthesis, and protocols for treating the Wieland-Miescher ketone are worthy to be addressed. The presented review provides the progress of the usage of Wieland-Miescher ketone for the total synthesis, while treatments on C=C and C=O in the Wieland-Miescher ketone at the beginning of total synthesis are exemplified herein. Modifications of the Wieland-Miescher ketone are composed of oxidation, reduction, and electrophilic or nucleophilic addition. In addition, protection of non-conjugated C=O with glycol or protection of conjugated C=O with ethanedithiol, and the introduction of substituents into α-position of C=C can also be used to modify the structure of the Wieland-Miescher ketone. It is reasonably believed that many novel strategies will be found to treat the Wieland-Miescher ketone in the future total synthesis.

γ-Ketosulfides and Hydroxysulfides from Sodium Methanthiolate of Sulfidic Spent Caustics

Condensation of pentan-3-one, hexan-2-one, 4-methylpentan-2-one, 5-methylhexan-3-one, or 2,6-dimethylheptan-4-one with formaldehyde and sodium methanethiolate, which is present in sulfidic spent caustic from the Orenburg gas processing plant, yields the corresponding mono- and bis[(methylsulfanyl)methyl]-substituted ketones or their mixtures depending on the reactant ketone structure. Alkylthiomethylation of butan-2-one with equimolar amounts of formaldehyde and sodium methanethiolate results in 3-methyl-5-thiahexan-2-one or, in the case of a twofold excess of the reagents, in 2-methyl-1,5-bis(methylsulfanyl)-4-[(methylsulfanyl)methyl]pentan-3-one. On the basis of 3-methyl-5-thiahexan-2-one, new polyfunctional [(methylsulfanyl)methyl]-substituted alcohol, α-hydroxymethylketone, 1,3-diol, and 1,3-dioxane have been obtained.

Characterisation of bio-oil and its sub-fractions from catalytic fast pyrolysis of biomass mixture.

The present study aim is to characterise catalytic and non-catalytic biomass pyrolysis liquid products. Turkey is the world's largest hazelnut producer and also ranks fifth in tea production, so a mixture of hazelnut shell, tea bush and hazelnut knot was selected as the biomass sample, and vanadium pentoxide (V2O5) was also used as a catalyst. Considering the biomass mixture and catalyst used, this research is unique for the literature. Bio-oils, which are obtained by catalytic and non-catalytic processes and collected in two sub-fractions, were characterised. The sub-fractions of toluene and ethyl acetate, there was a significant increase in calorific values compared with the mixture without catalyst, because of the decrease in the amount of oxygen and increase in the amount of carbon. The increase in this calorific value in the toluene sub-fraction is about 76% higher than the raw material mixture. In the sub-fractions of toluene and ethyl acetate produced by catalytic pyrolysis, an increase in carbon content was observed when compared with non-catalytic products, while the amounts of oxygen decreased. Considering the results, the toluene sub-fraction is generally composed of phenolic structures. Generally, the ethyl acetate sub-fraction comprises the carbonyl group - containing ketone and aldehyde structures as well as aromatic and phenolic compounds. The resulting bio-oil has the potential to be used as a liquid fuel both in terms of calorific values and in terms of the H/C and O/C ratio.

The Sulfonated Styrene-Acrylic Acid Copolymers with pH-Indicator Property

In this study, a polymer pH-indicator was synthesized by sulfonation of poly(styrene-co-acrylic acid) with concentrated sulfuric acid. The synthesized polymer pH-indicator exhibited pH-responsive color changes in aqueous solutions, being purple in alkaline medium (pH 9). The sulfonation process extent and polymer color were affected by time and temperature of the process, as well as acrylic acid (AA) content. The addition of acrylic acid was a crucial point for color change due to the facility of cyclic ketone structure to turn into phenol under acidic condition. Compared with low molecule pH-indicators, the sulfonated copolymer was prepared in form of films being repeatedly used as pH-indicator and easily removed from the acid-base medium.

Half‒Sandwich (η6‒p‒Cymene) Ruthenium(II) complexes bearing 5‒Amino‒1‒Methyl‒3‒Phenylpyrazole Schiff base ligands: Synthesis, structure and catalytic transfer hydrogenation of ketones

New (η6‒p‒cymene) ruthenium(II) complexes containing Schiff base ligands of the general composition [RuCl(η6‒p‒cymene)(L1‒3)] have been synthesized. The complexes were characterized by analytical and spectral (FT‒IR, UV–Vis, 1H NMR and 13C NMR) methods. The molecular structure of the representative complex [RuCl(η6‒p‒cymene)(L3)] 6 was determined by single crystal X−ray diffraction studies, revealing a pseudo-octahedral piano stool geometry around ruthenium(II) ion. Further, one of the complexes 6 was screened for their efficiency as a catalyst in the transfer hydrogenation of various ketones to alcohols in the presence of KOH and 2‒propanol showed an excellent conversion up to 99%. Under the optimized conditions, the influence of base, reaction temperature and substrate scope was also reported.

Clopidogrel as a donor probe and thioenol derivatives as flexible promoieties for enabling H2S biomedicine

Hydrogen sulfide has emerged as a critical endogenous signaling transmitter and a potentially versatile therapeutic agent. The key challenges in this field include the lack of approved hydrogen sulfide-releasing probes for in human exploration and the lack of controllable hydrogen sulfide promoieties that can be flexibly installed for therapeutics development. Here we report the identification of the widely used antithrombotic drug clopidogrel as a clinical hydrogen sulfide donor. Clopidogrel is metabolized in patients to form a circulating metabolite that contains a thioenol substructure, which is found to undergo spontaneous degradation to release hydrogen sulfide. Model studies demonstrate that thioenol derivatives are a class of controllable promoieties that can be conveniently installed on a minimal structure of ketone with an α-hydrogen. These results can provide chemical tools for advancing hydrogen sulfide biomedical research as well as developing hydrogen sulfide-releasing drugs.

Copper-Catalyzed [2 + 3] Cyclization of α-Hydroxyl Ketones and Arylacetonitriles: Access to Multisubstituted Butenolides and Oxazoles

A copper-catalyzed [2 + 3] formal cyclization reaction between α-hydroxyl ketones and arylacetonitriles has been developed. The reaction outcome was ultimately dependent on the structure of the α-hydroxy ketones employed. Tertiary α-hydroxy ketones gave 3,4,5,5-tetrasubstituted butenolides as the sole products, while secondary α-hydroxy ketones furnished 2,4,5-trisubstituted oxazoles selectively. This method has many advantages, such as the use of easily available substrates, broad substrate scope, good functional tolerance, and milder reaction conditions.

Fragmentation Pathways of Lithiated Hexose Monosaccharides.

We characterize the primary fragmentation reactions of three isomeric lithiated D-hexose sugars (glucose, galactose, and mannose) utilizing tandem mass spectrometry, regiospecific labeling, and theory. We provide evidence that these three isomers populate similar fragmentation pathways to produce the abundant cross-ring cleavage peaks (0,2A1 and 0,3A1). These pathways are highly consistent with the prior literature (Hofmeister et al. J. Am. Chem. Soc. 113, 5964-5970, 1991, Bythell et al. J. Am. Soc. Mass Spectrom. 28, 688-703, 2017, Rabus et al. Phys. Chem. Chem. Phys. 19, 25643-25652, 2017) and the present labeling data. However, the structure-specific energetics and rate-determining steps of these reactions differ as a function of precursor sugar and anomeric configuration. The lowest energy water loss pathways involve loss of the anomeric oxygen to furnish B1 ions. For glucose and galactose, the lithiated α-anomers generate ketone structures at C2 in a concerted reaction involving a 1,2-migration of the C2-H to the anomeric carbon (C1). In contrast, the β-anomers are predicted to form 1,3-anhydroglucose/galactose B1 ion structures. Initiation of the water loss reactions from each anomeric configuration requires distinct reactive conformers, resulting in different product ion structures. Inversion of the stereochemistry at C2 has marked consequences. Both lithiated mannose forms expel water to form 1,2-anhydromannose B1 ions with the newly formed epoxide group above the ring. Additionally, provided water loss is not instantaneous, the α-anomer can also isomerize to generate a ketone structure at C2 in a concerted reaction involving a 1,2-migration of the C2-H to C1. This product is indistinguishable to that from α-glucose. The energetics and interplay of these pathways are discussed. Graphical Abstract ᅟ.

Preparation of chiral phenylethanols using various vegetables grown in Algeria

Abstract Ginger root, strawberry tree and mandarin growing in Algeria were evaluated for their ability to stereoselective reduction of prochiral ketones. The reactivity and the enantioselectivity are strongly dependent on the biocatalyst used, and the structure of ketone. High enantioselectivities were observed for some substrates (70–99% ee) especially for the bioreduction of acetophenone 1, p-chloroacetophenone 2, tetralone 5, thiochromanone 6 and chromanone 7. Using two different batchs of Citrus reticulata from two regions of our country Annaba and Skikda, the corresponding optically active alcohols were obtained with high enantioselectivity and Skikda's variety was the best biocatalyst. The results reveal that these plants species can be a promising biocatalysts for the production of key intermediates.

Visible-Light-Enabled Preparation of Palladium Nanoparticles and Application as Catalysts for Suzuki-Miyaura Coupling.

Silyl ketones were used for the preparation of palladium nanoparticles (PdNPs) starting with Pd(OAc)2 in dimethylformamide under irradiation with a visible light-emitting diode (LED). Variation of the silyl ketone structure allowed adjustment of the PdNP diameter (1.9 or 5.2 nm). The in situ-formed PdNPs were further stabilized with polyvinylpyrrolidone and then applied as recyclable catalysts in the Suzuki-Miyaura coupling of arylboronic acids with aryl iodides to obtain substituted biphenyls in excellent yields.

Gas-Phase Oxidation of the Protonated Uracil-5-yl Radical Cation.

This study targets the kinetics and product detection of the gas-phase oxidation reaction of the protonated 5-dehydrouracil (uracil-5-yl) distonic radical cation using ion-trap mass spectrometry. Protonated 5-dehydrouracil radical ions (5-dehydrouracilH+ radical ion, m/z 112) are produced within an ion trap by laser photolysis of protonated 5-iodouracil. Storage of the 5-dehydrouracilH+ radical ion in the presence of controlled concentration of O2 reveals two main products. The major reaction product pathway is assigned as the formation of protonated 2-hydroxypyrimidine-4,5-dione (m/z 127) + •OH. A second product ion (m/z 99), putatively assigned as a five-member-ring ketone structure, is tentatively explained as arising from the decarbonylation (-CO) of protonated 2-hydroxypyrimidine-4,5-dione. Because protonation of the 5-dehydrouracil radical likely forms a dienol structure, the O2 reaction at the 5 position is ortho to an -OH group. Following this addition of O2, the peroxyl-radical intermediate isomerizes by H atom transfer from the -OH group. The ensuing hydroperoxide then decomposes to eliminate •OH radical. It is shown that this elimination of •OH radical (-17 Da) is evidence for the presence of an -OH group ortho to the initial phenyl radical site, in good accord with calculations. The subsequent CO loss mechanism, to form the aforementioned five-member-ring structure, is unclear, but some pathways are discussed. By following the kinetics of the reaction, the room temperature second-order rate coefficient of the 5-dehydrouracilH+ distonic radical cation with molecular oxygen is measured at 7.2 × 10-11 cm3 molecule-1 s-1, Φ = 12% (with ±50% total accuracy). For aryl radical reactions with O2, the presence of the •OH elimination product pathway, following the peroxyl-radical formation, is an indicator of an -OH group ortho to the radical site.

Peculiarities of the reactions of a,b-unsaturated g-bromoketones with hydrazine derivatives

The reaction result of a,b-unsaturated g-bromoketones with hydrazines depends on the structure of the reagents. Reaction with hydrazine hydrate leads to the mixture of 3,5- di(R)pyridazine, 3,6-di(R)pyridazine and 2,4-di(R)-1H-pyrrol-1-amine derivatives. The formation of three types of products is due to the structure of the unsaturated aliphatic ketone. Two competing reaction schemes of ketones with hydrazines are considered, which include condensation or Michael-type addition in the first stage. The main products of the reactions of halogen-substituted derivatives of g-bromodipnone with arylhydrazines are 1,3,5-triaryl-1,6-dihydropyridazines, which easily form aromatic salts under reaction conditions (when heated in EtOH).

Bio-ketones from lignocellulosic biomass: experimental investigation on fuel properties, combustion and emissions characteristics of cyclopentanone blend with diesel in compression ignition engine

Use of alternative fuels in compression ignition engines is the topic for many studies. This paper presents the results of lubricity, calorific value, viscosity, surface tension and density of a ketone blend with diesel to use as a fuel in compression ignition engine. Analyses of fuel properties are vital due to their effect on fuel system. In addition, this study is related to the development of future biofuels and it indicates the effect of oxygen double bond in molecular structure of ketones on important fuel properties. Cyclopentanone which has cyclic molecular structure was used; it can be produced from lignocellulosic biomass through various processing ways. This ketone was blended with diesel fuel at 10% vol. Results from fuel properties tests were compared to the conventional diesel fuel. In the next step this blend was tested in a research diesel engine to analyse its combustion behaviour and emission characteristics of exhaust gases; these results were compared with ultra-low sulphur diesel fuel. Results showed that cyclopentanone, as an additive to diesel, improved surface tension and density of the fuel but in contrast had negative effect on viscosity, lubricity and calorific value of the fuel, but still in the standard range. Combustion behaviour of this fuel in the diesel engine also showed longer ignition delay of ketone blend and also that gaseous emission such as CO and THC are higher than from diesel fuel and NOx emission is less than from conventional diesel fuel combustion.

Ruthenium Lewis Acid‐Catalyzed Asymmetric Diels–Alder Reactions: Reverse‐Face Selectivity for α,β‐Unsaturated Aldehydes and Ketones

Acrolein, methacrolein, methyl vinyl ketone, ethyl vinyl ketone, 3‐methyl‐3‐en‐2‐one, and divinyl ketone were coordinated to a cationic cyclopentadienyl ruthenium(II) Lewis acid incorporating the electron‐poor bidentate BIPHOP–F ligand. Analysis by NOESY and ROESY NMR techniques allowed the determination of conformations of enals and enones present in solution in CD2Cl2. The results were compared to solid‐state structures and to the facial selectivities of catalytic asymmetric Diels–Alder reactions with cyclopentadiene. X‐Ray structures of four Ru‐enal and Ru‐enone complexes show the α,β‐unsaturated C=O compounds to adopt an anti‐s‐trans conformation. In solution, enals assume both anti‐s‐trans and anti‐s‐cis conformations. An additional conformation, syn‐s‐trans, is present in enone complexes. Enantioface selectivity in the cycloaddition reactions differs for enals and enones. Reaction products indicate enals to react exclusively in the anti‐s‐trans conformation, whereas with enones, the major product results from the syn‐s‐trans conformation. The alkene in s‐cis conformations, while present in solution, is shielded and cannot undergo cycloaddition. A syn‐s‐trans conformation is found in the solid state of the bulky 6,6‐dimethyl cyclohexanone‐Ru(II) complex. The X‐ray structure of divinyl ketone is unique in that the Ru(II) center binds the enone via a η2 bond to one of the alkene moieties. In solution, coordination to Ru–C=O oxygen is adopted. A comparison of facial preference is also made to the corresponding indenyl Lewis acids.

Toxicity studies of octahydro-tetramethyl-naphthalenyl-ethanone (OTNE) administered dermally to F344/NTac rats and B6C3F1/N mice.

Octahydro-tetramethyl-naphthalenyl-ethanone (OTNE) is a fragrance ingredient that is formed as a mixture of isomers with a basic unsaturated alkyl cyclic ketone structure. The main isomer is 1-(1,2,3,4,5,6,7,8-octahydro-2,3,8,8-tetramethyl-2-naphthalenyl)ethanone (β-isomer). Two other predominant isomers within the mixture are 1-(1,2,3,4,6,7,8,8a-octahydro-2,3,8,8-tetramethyl-2-naphthalenyl)ethanone (α-isomer) and 1-(1,2,3,5,6,7,8,8a-octahydro-2,3,8,8-tetramethyl-2-naphthalenyl)ethanone (γ-isomer). OTNE is used as a perfume ingredient in soap, shampoo, cologne, liquid detergent compounds, and malodor-reducing compounds. Male and female F344/NTac rats and B6C3F1/N mice were administered OTNE (greater than 92.3% pure with respect to the 3 prominent isomers) dermally for 3 months. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, and rat and mouse peripheral blood erythrocytes. (Abstract Abridged).

Improved synthesis dimethylhomoecoerdianthrone (HOCD) and its functionalization through facile amination reactions

An improved synthesis of dimethylhomoecoerdianthrone (HOCD), a dye used for singlet oxygen detection, was reported by isolation of a key intermediate followed by cyclization reaction. Moreover, dehydrogenative amination reaction between HOCD and alkyl amines and diamines resulted in amine functionalized HOCD derivatives with good yield. The observed reactivity depends on the nucleophilicity of amine and electrophilicity of HOCD. DFT calculations suggest that the reaction involves 1,4-Michael addition followed by migration of hydrogen atom due to aromatization. Under the aerated conditions, dehydrogenation occurs to restore the ketone structure. This C-N coupling reaction can be utilized to construct molecular materials with near infrared photonic properties. Finally, we illustrated that the HOCD derives, HOCD-SO3−, can be grafted to semiconductor nanocrystals (quantum dots) to give turn-on fluorescent nanoprobe for highly selective detection of singlet oxygen.

The synthesis and analysis of lignin-bound Hibbert ketone structures in technical lignins.

Understanding the structure of technical lignins resulting from acid-catalysed treatment of lignocellulosic biomass is important for their future applications. Here we report an investigation into the fate of lignin under acidic aqueous organosolv conditions. In particular we examine in detail the formation and reactivity of non-native Hibbert ketone structures found in isolated organosolv lignins from both Douglas fir and beech woods. Through the use of model compounds combined with HSQC, HMBC and HSQC-TOCSY NMR experiments we demonstrate that, depending on the lignin source, both S and G lignin-bound Hibbert ketone units can be present. We also show that these units can serve as a source of novel mono-aromatic compounds following an additional lignin depolymerisation reaction.

Inherent flame retardation of semi-aromatic polyesters via binding small-molecule free radicals and charring

Semi-aromatic polyesters containing special aryl ether and/or ketone structures show good flame retardancy via binding small-molecule free radicals and forming char during combustion.

Electronic structure and tautomerism of aryl ketones

The electronic structures of several aryl ketones (AK) and their α-halo derivatives have been studied by UV photoelectron spectroscopy (UPS). The relative stabilities of keto–enol tautomers have been determined using high-level ab initio calculations and the results were used in the analysis of UPS spectra. The main features of electronic structure and tautomerism of the AK derivatives are discussed.

Xanthohumol, a polyphenol chalcone present in hops, activating Nrf2 enzymes to confer protection against oxidative damage in PC12 cells.

quinone oxidoreductase, thioredoxin, and thioredoxin reductase. A mechanistic study indicates that the α,β-unsaturated ketone structure in Xn and activation of the transcription factor Nrf2 are key determinants for the cytoprotection of Xn. Targeting the Nrf2 by Xn discloses a previously unrecognized mechanism underlying the biological action of Xn. Our results demonstrate that Xn is a novel small-molecule activator of Nrf2 in neuronal cells and suggest that Xn might be a potential candidate for the prevention of neurodegenerative disorders.