Series Of Ketones Research Articles

Efficient Ru(II)-catalyzed asymmetric hydrogenation of simple ketones with C2-symmetric planar chiral metallocenyl phosphinooxazoline ligands

C2-symmetric metallocenyl planar phosphinooxazoline ligands (2 and 3) have been applied in the Ru(II)-catalyzed asymmetric hydrogenation of simple ketones. This type of ligands enjoys the advantages of dual reaction sites as well as larger steric hindrance than their corresponding C1-symmetric counterparts. As a result, almost quantitative conversions and excellent enantioselectivities were obtained for a series of simple ketones. Under the optimal reaction conditions, up to 99.7% ee was obtained in many cases. It was also confirmed that hydrogen rather than reaction solvent i-PrOH is at work in the hydrogenation procedure.

Convenient and efficient decarboxylative aldol reaction of malonic acid half esters with trifluoromethyl ketones

A convenient and efficient decarboxylative ketone aldol condensation of malonic acid half esters was reported. In the presence of catalytic amount of triethylamine, a series of aromatic and alkyl trifluoromethyl ketones were transformed into the desired adducts in 61–99% yields. In a preliminary experiment, a moderate stereoselectivity was obtained. Direct reduction of the aldol product with LiAlH4 afforded trifluoromethylated 1,3-diol.

Prediction of retention times in comprehensive two-dimensional gas chromatography using thermodynamic models

A method was developed to accurately predict both the primary and secondary retention times for a series of alkanes, ketones and alcohols in a flow-modulated GC×GC system. This was accomplished through the use of a three-parameter thermodynamic model where ΔH, ΔS, and ΔCp for an analyte's interaction with the stationary phases in both dimensions are known. Coupling this thermodynamic model with a time summation calculation it was possible to accurately predict both 1tr and 2tr for all analytes. The model was able to predict retention times regardless of the temperature ramp used, with an average error of only 0.64% for 1tr and an average error of only 2.22% for 2tr. The model shows promise for the accurate prediction of retention times in GC×GC for a wide range of compounds and is able to utilize data collected from 1D experiments.

Synthesis and StructureActivity Relationships of Antifungal Crassinervic Acid Analogs

A series of analogs of the natural antifungal compound crassinervic acid, a constituent of Piper crassinervium, were synthesized to gain insight into the most relevant structural features affecting the activity of the parent molecule. Most compounds were prepared by aldol reaction of methyl 3-acetyl-4-hydroxybenzoate with a series of ketones, followed by reduction, hydrolysis, and oxidation. The antifungal activities of crassinervic acid and its analogs was assessed against Cladosporium cladosporioides by using the method of bioautography. The bioassay results allowed us to depict structureactivity relationships for this class of compounds.

Pheromonal Mediation of Intraseasonal Declines in the Attractivity of Female Red-Sided Garter Snakes, Thamnophis sirtalis parietalis

During the breeding season, female red-sided garter snakes (Thamnophis sirtalis parietalis) produce and express a sexual attractiveness pheromone that elicits male courtship behavior. Composed of a homologous series of saturated and monounsaturated methyl ketones, this pheromone is expressed in female skin lipids. Recent studies have shown that the sexual attractivity of unmated female garter snakes declines as the breeding season progresses. Here, we investigated whether temporal changes in the quantity and/or quality of the female sexual attractiveness pheromone are responsible for the observed loss of attractivity. Female red-sided garter snakes were collected immediately following spring emergence and held under natural conditions for the duration of the breeding season. Behavioral experiments confirmed that unmated females become significantly less attractive to males within two weeks of emergence from hibernation. Additionally, these females had lower estradiol concentrations at two weeks post-emergence. Subsequent chemical analyses revealed qualitative variation between the pheromone profiles of newly emerged females and those of females at two weeks post-emergence. Together, these results support the hypothesis that changes in the female sexual attractiveness pheromone are responsible for declining post-emergence female attractivity in garter snakes.

A continuous process for the reductive deoxygenation of aromatic ketones over Cu30Cr10/γ-Al2O3

A continuous process for reduction of aromatic ketones to the corresponding aromatic alkanes over Cu30Cr10/γ-Al2O3 was established in a fixed-bed reactor. A series of aromatic ketones were examined, and all of the corresponding aromatic hydrocarbons were obtained in more than 95% yield. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and H2-temperature programmed reduction. Cu0 is believed to be the active center of the catalyst. Cr was found to have an important effect on catalytic activity and stability.

Design, Synthesis, and Bioactivities Screening of a Diaryl Ketone‐Inspired Pesticide Molecular Library as Derived from Natural Products

Three natural products, 1,5-diphenylpentan-1-one, 1,5-diphenylpent-2-en-1-one, and 3-hydroxy-1,5-diphenylpentan-1-one, with good insecticidal activities were extracted from Stellera chamaejasme L. Based on their shared diaryl ketone moiety as 'pharmacophores', a series of diaryl ketones were synthesized and tested for insecticidal activity, acetylcholinesterase inhibitory activity, and antifungal activity. All synthesized compounds showed poor insecticidal and acetylcholinesterase inhibitory activities. Compound III with a furyl ring showed strong activities against plant pathogenic fungi. The IC(50) of compound (E)-1-(2,4-dichlorophenyl)-3-(furan-2-yl)- -prop-2-en-1-one (III(2) ) was 1.20 mg/L against Rhizoctonia solani, suggesting its strong potential as a novel antifungal drug.

Facile synthesis of 4-acetyl-coumarins, -thiocoumarin and -quinolin-2(1 H)-one via very high α-regioselective Heck coupling on tosylates

An efficient synthesis of a series of methyl ketones at the C4 position of coumarins, coumarin-containing heterocycles and analogous scaffolds is reported via very high α-regioselective Heck coupling using tosylates and in very high yields. Although α-regioselectivity in Heck coupling can be obtained with triflates as substrates, tosylates are less toxic, less expensive and, importantly, more stable.

Amphiphilic polymeric Michler's ketone (MK) photoinitiators (APMKs) containing PEO chain and coinitiator amine

AbstractA series of amphiphilic polymeric Michler's ketone (MK) photoinitiators (APMKs) were synthesized by incorporating PEO short chain, MK moiety, and coinitiator amine into the same polymeric chain. APMKs possess good amphiphilic ability and become water‐soluble when the molar ratio of MK(pipaz)2/PEO/piperazine is 2:3:1. UV–Vis measurement shows that APMKs possess the same characteristic absorption to MK derivatives. The photopolymerization of three monomers with different functionality and hydrophilicity, polyethylene glycol diacrylate (PEGDA), phenoxy ethyl acrylate (AMP‐10G), and 2,2‐bis[4‐(acryloxypolyethoxy)phenyl]propane (A‐BPE‐10) initiated by APMKs was investigated by photodifferential scanning (photo‐DSC). The results show that APMKs can photoinitiate the polymerization of hydrophilic and hydrophobic monomers efficiently. As for photopolymerization of water‐soluble PEGDA, the final conversion is higher than 94%. Therefore, APMKs will be expected to find potential in many fields. Copyright © 2009 John Wiley & Sons, Ltd.

Exploiting the Facile Release of Trifluoroacetate for the α-Methylenation of the Sterically Hindered Carbonyl Groups on (+)-Sclareolide and (−)-Eburnamonine

An efficient method for the α-methylenation of carbonyl groups is reported, and this transformation is accomplished by a facile elimination of trifluoroacetate during the formation of the olefin. This method represents an improvement beyond existing protocol in cases of steric hindrance, and we have demonstrated the utility of the process across a series of ketones, lactams, and lactones. Additionally, we have applied this method to produce semisynthetic derivatives of the natural products (+)-sclareolide and (-)-eburnamonine, in which the carbonyl group is proximal to bulky functional groups. Mechanistic insight is also provided from a time course of (19)F NMR. Biological evaluation of the natural-product-derived enones led to the identification of a derivative of (-)-eburnamonine with significant cytotoxicity (LC(50) = 14.12 μM) in drug-resistant MDA-MB-231 breast cancer cells.

Reductive coupling of carbonyl compounds promoted by cobalt or titanium nanoparticles

The reaction of a series of aldehydes and ketones with readily prepared cobalt or titanium nanoparticles, under mild reaction conditions, led to the obtention of different reductive dimerization products depending on the nature of the transition metal used. Cobalt nanoparticles (CoNPs) allowed the selective transformation of the starting carbonyl compounds into vicinal diols, whereas the reaction promoted by titanium nanoparticles (TiNPs) led to the formation of the corresponding alkenes. In this last case, the use of trimethylsilyl chloride (TMSCl) as additive, at 0 oC, also allowed the obtention of vicinal diols after acidic aqueous work-up.

Asymmetric Chemoenzymatic Synthesis of Miconazole and Econazole Enantiomers. The Importance of Chirality in Their Biological Evaluation

A simple and novel chemoenzymatic route has been applied for the first time in the synthesis of miconazole and econazole single enantiomers. Lipases and oxidoreductases have been tested in stereoselective processes; the best results were attained with oxidoreductases for the introduction of chirality in an adequate intermediate. The behaviors of a series of ketones and racemic alcohols in bioreductions and acetylation procedures, respectively, have been investigated; the best results were found with alcohol dehydrogenases A and T, which allowed the production of (R)-2-chloro-1-(2,4-dichlorophenyl)ethanol in enantiopure form under very mild reaction conditions. Final chemical modifications have been performed in order to isolate the target fungicides miconazole and econazole both as racemates and as single enantiomers. Biological evaluation of the racemates and single enantiomers has shown remarkable differences against the growth of several microorganisms; while (R)-miconazole seemed to account for most of the biological activity of racemic miconazole on all the strains tested, both enantiomers of econazole showed considerable biological activities. In this manner, (R)-econazole showed higher values against Candida krusei , while higher values were observed for (S)-econazole against Cryptococcus neoformans, Penicillium chrysogenum, and Aspergillus niger.

Synthesis of Triphenylamine-Modified Arylates and Ketones via Suzuki Coupling Reactions

A series of triphenylamine-mdified arylates and ketones were synthesized via Pd-catalyzed Suzuki coupling reaction of triphenylamine boronic acid with aryl bromide. The triphenylamine boronic acid was synthesized by iodization of 4-bromoaniline, Ullmann reaction of 1-bromo-4-iodobenzene with diphenylamine, and boronic acidification of 4-bromotriphenylamine.

Mild and efficient barbier allylation reaction mediated by magnesium powder under solvent-free conditions

A novel and highly efficient synthesis of homoallylic alcohols is achieved by the allylation of carbonyl compounds using magnesium powder as mediator under solvent-free conditions. A series of aldehydes and ketones are converted to the corresponding homoallylic alcohols, the yields of the reaction is considerably high (85–98%). The procedure is environment benign, operationally simple and easy to scale up at room temperature.

A parallel Ugi reaction at students laboratories in the Ural and Moscow

A four-component Ugi reaction was adapted for students education. To this end, a series of almost odorless aromatic isonitriles with donor substituents was reacted with a specific carboxylic acid, phthaloyl glycine, to obtain poorly soluble (although nicely crystallized) products. The process was performed and compared in two versions by using (1) a standard centrifuge for parallel separation of precipitates and (2) parallel filtration with SynCore apparatus. It is shown for a broad series of aliphatic ketones and benzyl amines that the yields are satisfactory and the products require no further purification.

Mannich Reaction of Imines and Silyl Enol Ethers Induced by Radical Cation Salts: Synthesis of β-Amino Ketones

Mannich reaction of imines and sily enol ethers induced by radical cation salts was investigated and a series of β-amino ketones were synthesized. Reverse diastereoselectivity was obtained in the reactions of imines and silyl enol ethers of pentan-2-one and pentan-3-one, respectively, which was rationalized by quantum mechanical calculations. A single electron-transfer mechanism was proposed in which the imine radical cation acts as an electrophilic species in this transformation.

A Better Sunscreen: Structural Effects on Spectral Properties

A modification of the mixed-aldol synthesis of dibenzylideneacetone, prepared from acetone and benzaldehyde, is described wherein acetone is replaced with a series of cyclic ketones with ring sizes of 5−7 carbons. The structural variations in the resulting conjugated ketones produce regular variations in the UV−vis absorption spectra. The choice of the best sunscreen agent based on these variations is straightforward, and by considering simple molecular orbital diagrams in the context of the molecular geometries, students can go the next step and understand why the variation occurs.

A halide-initiated aza-Baylis–Hillman reaction: generation of unnatural amino acids

A series of allenic ketones react with a glyoxylate-derived imine in the presence of MgBr 2 through an aza-Morita–Baylis–Hillman (MBH) reaction. The isolation of a variety of unnatural amino acids with unique allene-containing functional groups provides a conceptually new application of the aza-MBH. The reaction scope and preliminary mechanistic investigations are discussed.

Ketone–Alcohol Hydrogen‐Transfer Equilibria: Is the Biooxidation of Halohydrins Blocked?

To ensure the quasi-irreversibility of the oxidation of alcohols coupled with the reduction of ketones in a hydrogen-transfer (HT) fashion, stoichiometric amounts of α-halo carbonyl compounds have been employed as hydrogen acceptors. The reason that these substrates lead to quasi-quantitative conversions has been tacitly attributed to both thermodynamic and kinetic effects. To provide a clear rationale for this behavior, we investigate herein the redox equilibrium of a selected series of ketones and 2-propanol by undertaking a study that combines experimental and theoretical approaches. First, the activity of the (R)-specific alcohol dehydrogenase from Lactobacillus brevis (LBADH) with these substrates was studied. The docking of acetophenone/(R)-1-phenyethanol and α-chloroacetophenone/(S)-2-chloro-1-phenylethanol in the active site of the enzyme confirms that there seems to be no structural reason for the lack of reactivity of halohydrins. This assumption is confirmed by the fact that the corresponding aluminum-catalyzed Meerwein-Ponndorf-Verley-Oppenauer (MPVO) reactions afford similar conversions to those obtained with LBADH, showing that the observed reactivity is independent of the catalyst employed. While the initial rates of the enzymatic reductions and the IR ν(C=O) values contradict the general belief that electron-withdrawing groups increase the electrophilicity of the carbonyl group, the calculated ΔG values of the isodesmic redox transformations of these series of ketones/alcohols with 2-propanol/acetone support the thermodynamic control of the reaction. As a result, a general method to predict the degree of conversion obtained in the HT-reduction process of a given ketone based on the IR absorption band of the carbonyl group is proposed, and a strategy to achieve the HT oxidation of halohydrins is also shown.

ChemInform Abstract: The Diastereoselective Influences of Remote Substituents on Enolate Alkylations.

Abstract The methylation of a series of γ-oxygenated ketones enolates ( 3 ) has been examined with the result that poor to outstanding levels of diastereoselectivity are observed that appear to be predictably consistent with a general model for asymmetric electrophilic addition reactions.