Carbonyl Compounds In Presence Research Articles

Ein‐Topf‐Synthese von 1,3‐Cyclohexadienen durch Birch‐Reduktion in Gegenwart von Carbonylverbindungen

Ein‐Topf‐Synthese von 1,3‐Cyclohexadienen durch Birch‐Reduktion in Gegenwart von Carbonylverbindungen

One-Pot Synthesis of 1,3-Cyclohexadienes by Birch Reduction in the Presence of Carbonyl Compounds.

Birch reductions are well-known transformations of arenes, applied for large scale synthesis of 1,4-cyclohexadienes. Herein, we describe first reactions of benzoic acids in the presence of carbonyl compounds, affording aldol products in moderate to high yields. Alkyl aldehydes give the expected nonconjugated dienes by reaction at the α-position. Interestingly, the intermediately formed enolate attacks aryl aldehydes and ketones from its γ-position, which can be explained by steric hindrance. This opens the door for the one-pot synthesis of 1,3-cyclohexadienes, which are not accessible by classical Birch reductions. Our method is applicable to benzoic, m- and p-toluic acid and various carbonyl compounds, and more than 25 new products were isolated in up to 93 % yield. Prochiral aryl aldehydes afford diastereomeric mixtures in ratios of about 4 : 1, but in the cyclohexadiene ring only trans isomers are formed with high selectivity. Finally, the 1,3-cyclohexadienes are suitable precursors for further transformations, which we have demonstrated in first examples. Thus, aromatization affords products of a formal meta selective Friedel-Crafts alkylation, and four new stereocenters were generated by cycloaddition of singlet oxygen with excellent selectivity.

Role of Carbonyl Compounds for N-Nitrosamine Formation during Nitrosation: Kinetics and Mechanisms.

N-Nitrosamines are potential human carcinogens frequently detected in natural and engineered aquatic systems. This study sheds light on the role of carbonyl compounds in the formation of N-nitrosamines by nitrosation of five secondary amines via different pathways. The results showed that compared to a control system, the presence of formaldehyde enhances the formation of N-nitrosamines by a factor of 5-152 at pH 7, depending on the structure of the secondary amines. Acetaldehyde showed a slight enhancement effect on N-nitrosamine formation, while acetone and benzaldehyde did not promote nitrosation reactions. For neutral and basic conditions, the iminium ion was the dominant intermediate for N-nitrosamine formation, while carbinolamine became the major contributor under acidic conditions. Negative free energy changes (<-19 kcal mol-1) and relatively low activation energies (<18 kcal mol-1) of the reactions of secondary amines with N2O3, iminium ions with nitrite and carbinolamines with N2O3 from quantum chemical computations further support the proposed reaction pathways. This highlights the roles of the iminium ion and carbinolamine in the formation of N-nitrosamines during nitrosation in the presence of carbonyl compounds, especially in the context of industrial wastewater.

Green synthesis, characterization and biological activity of silver nanoparticles from Dicranum majus Turner

The exploitation of various plant compounds for the biosynthesis of nanoparticles is considered a green technology because it does not involve any harmful chemicals. In the current study, we synthesized and characterized silver nanoparticles from Dicranum majus (Dm) Turner, a moss plant (Bryophyte). The occurrence of the visible color change from red to brown confirmed Dm silver nanoparticles (DmAgNPs). The DmAgNPs were characterized based on Ultraviolet-Visible (UV-Vis) Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR). The morphology, size, and elemental analysis of the prepared silver nanoparticles were examined using Transmission Electron Microscope (TEM) and zeta potential (ZP). The distribution pattern of DmAgNPs particle size and stability were determined with the zeta potential analysis by zeta sizer. The maximum absorption of DmAgNPs was obtained at 422 nm by UV-Vis spectrometer. The presence of carbonyl compounds was demonstrated by FTIR, TEM. Zeta sizer analysis revealed the average size of the nanoparticles as 278.7 nm with -16.7 mV zeta potential demonstrates moderate stability. Considering its antibacterial activities, DmAgNP is more effective on Enterococcus faecalis (ATCC 29212), Listeria monocytogenes (ATCC 7644), and Proteus vulgaris (NRRL B-123) bacteria; it has no mutagenic activity; cleaved DNA as a result of gel electrophoresis; Antioxidant activity was determined by the 2,2-Diphenyl-1- picrylhydrazyl (DPPH) method.

Ruthenium-catalysed multicomponent synthesis of the 1,3-dienyl-6-oxy polyketide motif.

Polyketide natural products are an important class of biologically active compounds. Although substantial progress has been made on the synthesis of repetitive polyketide motifs through the iterative application of a single reaction type, synthetic access to more diverse motifs that require more than one type of carbon-carbon bond connection remains a challenge. Here we describe a catalytic, multicomponent method for the synthesis of the privileged polyketide 1,3-dienyl-6-oxy motif. The method allows for the formation of two new carbon-carbon bonds and two stereodefined olefins. It generates products that contain up to three contiguous sp3 stereocentres with a high stereoselectivity in a single operation and can be used to generate chiral products. The successful development of this methodology relies on the remarkable efficiency of the ruthenium-catalysed alkene-alkyne coupling reaction between readily available vinyl boronic acids and alkynes to provide unsymmetrical 3-boryl-1,4-diene reagents. In the presence of carbonyl compounds, these reagents undergo highly diastereoselective allylations to afford the desired 1,3-dienyl-6-oxy motif and enable complex polyketide synthesis in a rapid and asymmetric fashion.

Influence of puffing conditions on the carbonyl composition of e-cigarette aerosols.

Owing to their harmful effects on human health, the presence of carbonyl compounds in e-cigarette aerosols raises concerns. To date, the reported concentration levels in e-vapors vary greatly between studies and several factors that markedly influence carbonyl emission during vaping have been highlighted including the heating temperature, the power supply, the device architecture, the filling level of the tank and the main e-liquid constituents. This study investigated the impact of puffing regimen parameters on the carbonyl composition of e-cigarette aerosols with the aim of: (1) better estimating the variability of carbonyl emissions depending on puffing conditions; (2) highlighting puffing profiles that increase the exposure to carbonyls; and (3) estimating to what extent puffing topography could be implied in the variability of carbonyl concentrations reported in the current literature. E-vapors from a single e-liquid were generated from two e-cigarette models with a smoking machine. A total of 7 different puffing regimens were used to individually study the influence of the puff volume, duration and frequency. Carbonyls were collected by DNPH cartridges and analysed by HPLC-UV. E-liquid consumption and e-vapor temperature were also monitored. E-vapor concentrations of formaldehyde, acetaldehyde, acetone, acrolein, propionaldehyde and methylglyoxal were affected, sometimes differently, by the modification of the puffing regimen, as well as by the e-cigarette model. For example, formaldehyde concentration ranged from 20 to 255 ng/puff depending on the puffing conditions. The results of principal component analyses, applied to the concentration data sets for the 6 carbonyls, suggest that the studied parameters interact and highlight some "carbonyl-emitting" combinations of concern (e-cigarette model/puffing regimen). However, the highest concentrations measured in the present study remain far lower than those observed in conventional cigarette mainstream smoke. This study confirms that the chosen puffing regimen contributes a part of the observed variability in the carbonyl levels reported in the scientific literature, hampering comparisons between studies and making interpretation difficult. Thus, harmonized and realistic protocols for the assessment of e-cigarette toxicity by physicochemical or experimental approaches are clearly needed.

A new oxidative reagent synthesis and its applications: Tetrakis-(2,4,6-trimethylpyridine)silver(I) dichromate (T-TMPSDC)

Tetrakis -(2,4,6-trimethylpyridine)silver(I) dichromate (T-TMPSDC) was easily synthesized by addition of 2,4,6-trimethylpyridine to an aqueous precipitation of silver dichromate and characterized thoroughly, using spectroscopic and others analytical methods such as FT-IR, 1 H NMR, 13 C NMR, DTA, SEM-EDS and XRD. When T-TMPSDC was used as an oxidative reagent, it showed selectivity in the oxidation of primary, secondary and benzylic alcohols to their corresponding carbonyl compounds in presence of benzylic carbons and arenes such as tetraline, anthracene and phenanthrene.

An insight into antimicrobial activity of the freshwater bryozoan Pectinatella magnifica

The antimicrobial activity of five crude extracts of the freshwater bryozoan Pectinatella magnifica (Leidy, 1851) was evaluated in vitro for the first time. P. magnifica acetone extract exhibited the highest antibacterial activity (minimum inhibitory concentrations (MIC) 0.004–0.350 mg/mL and MBC 0.007–0.500 mg/mL), while its methanol extract showed the most promising antifungal activity (MIC 0.03–0.12 mg/mL and MFC 0.06–0.25 mg/mL). Furthermore, at a concentration of 0.25 MIC, the methanol extract reduced biofilm formation of the bacterial strain Pseudomonas aeruginosa PAO1 in a considerable extent (59.14%). FTIR spectra of the most active extracts indicate the presence of carbonyl compounds, long-chain alcohols and/or sterols. According to the experimental data obtained, P. magnifica methanol extract may be considered as a good resource of novel natural products with potent antibiofilm activity against the bacterium well known for its resistance.

2,3-Dihydroquinazolin-4(1H)-one derivatives as potential non-peptidyl inhibitors of cathepsins B and H

A direct correlation between cathepsin expression–cancer progression and elevated levels of cathepsins due to an imbalance in cellular inhibitors-cathepsins ratio in inflammatory diseases necessitates the work on the identification of potential inhibitors to cathepsins. In the present work we report the synthesis of some 2,3-dihydroquinazolin-4(1H)-ones followed by their evaluation as cysteine protease inhibitors in general and cathepsin B and cathepsin H inhibitors in particular. 2,3-Dihydroquinazolin-4(1H)-ones, synthesized by the condensation of anthranilamide and carbonyl compound in presence of PPA-SiO2 catalyst, were characterized by spectral analysis. The designed compounds were screened as inhibitors to proteolysis on endogenous protein substrates. Further, a distinct differential pattern of inhibition was obtained for cathepsins B and H. The inhibition was more to cathepsin B with Ki values in nanomolar range. However, cathepsin H was inhibited at micromolar concentration. Maximum inhibition was shown by compounds, 1e and 1f for cathepsin B and compounds 1c and 1f for cathepsin H. The synthesized compounds were established as reversible inhibitors of cathepsins B and H. The results were also compared with the energy of interaction between enzyme active site and compounds using iGemdock software.

Formation of epoxides and N-arylaziridines via a simple Mg-Barbier reaction in DMF

The Mg-activation of benzal bromide 2b in DMF in the presence of carbonyl compounds 1 or imines 4 leads to epoxides 3 and N-arylaziridines 5, respectively, with acceptable isolated yields. It was found that DMF is likely involved in this process to form a nucleophilic intermediate by reaction with a first generated electrophilic carbene. Results obtained in this chemical approach are compared to those obtained using electrochemical activation, also in DMF.

Mn(III)acetate-Induced Electron Transfer in Pentaammine Cobalt(III)Complexes of α-Amino Acids in Micellar Medium

A micellar catalyzed oxidation of pentaamminecobalt(III) complexes of α-amino acids by Mn(III)acetate in acidic medium yielding nearly 100% Co(II) and about 100% carbonyl compounds are ultimate products. The unbound amino acids yield about 100% of carbonyl compound in presence of micelles. The effect of variation of sulphuric acid has been carried. The decrease in UV-Visible absorbance at λ=502 nm for Co(III) complex corresponds to nearly 100% of the initial absorbance. In spite of the stoichiometry of Mn(III) to unbound ligand is 2:1, the ratio of Mn(III) to cobalt(III) complex is 1:1 accounting for about 100% reduction at the cobalt(III) centre. The kinetic and stoichiometric results have been accounted. A suitable mechanism consistent with the experimental findings has been proposed by involving a radical cation intermediate.

Unlocking Hydrogenation for C-C Bond Formation: A Brief Overview of Enantioselective Methods.

Hydrogenation of π-unsaturated reactants in the presence of carbonyl compounds or imines promotes reductive C-C coupling, providing a byproduct-free alternative to stoichiometric organometallic reagents in an ever-increasing range of C=X (X = O, NR) additions. Under transfer hydrogenation conditions, hydrogen exchange between alcohols and π-unsaturated reactants triggers generation of electrophile-nucleophile pairs, enabling carbonyl addition directly from the alcohol oxidation level, bypassing discrete alcohol oxidation and generation of stoichiometric byproducts.

Mononuclear Ru(II) Carbonyl Complexes Containing Quadridentate Schiff Bases as N2O2 Donors: Synthesis, Spectral, Catalytic Properties, and Antibacterial Activity

Reactions of Ru3(CO)12with novel tetradentate Schiff bases ligands H2L1−5 in benzene under reduced pressure afforded the formation of new Ru(II) complexes of the type [Ru(CO)2(L1−5)] where L = anion of N,N/bis(salicylaldehyde)4,5-dimethyl-1, 2-phenylenediamine (saldmophn), N,N/bis(salicylaldehyde)4,5-dichloro-1,2-phenylenediamine (saldcophn), N,N/bis(salicylalde-hyde)2,3-diaminonaphthalene (saldnap), N,N/bis(o-vanillin)4, 5-dimethy-l,2-phenylenediamine (ovaldmophn), and N,N/bis(o-vanillin)4,5-dichloro-1,2-phenylenediamine (ovaldcophn), respectively. All the newly synthesized complexes were investigated using elemental analysis, FT-IR, UV-Vis, mass spectrometry, and magnetic measurements. An octahedral structure has been tentatively proposed for the new complexes. All the new complexes have been found to be efficient catalysts for oxidation of primary and secondary alcohols into corresponding carbonyl compounds in presence of N-methylmorpholine-N-oxide (NMO) as the source of oxygen. In view of the biological activity, the ligands showed moderate bactericidal activities, where upon chelation with ruthenium, the bactericidal activities increased and the results have been compared with some known antibiotics.

Effective oxidation of alcohols by Iron(III)-Schiff base-triphenylphosphine complexes

Iron(III)-Schiff base-triphenylphosphine complexes catalyze the oxidation of alcohols to their corresponding carbonyl compounds in presence of hydrogen peroxide in good yields.

ChemInform Abstract: Photolysis of Diazo(pentamethyldisilanyl)methyl Ketones in the Presence of Carbonyl Compounds: Trapping of the Acylsilene Intermediates.

UV photolysis of diazo(pentamethyldisilanyl)methyl ketones 1b – d generates acylsilenes (3-oxo-1-sila-1-propenes) 3 as reactive intermediates, which can be trapped by enolizable carbonyl compounds in an ene-type reaction. With non-enolizable carbonyl compounds or ethyl acetate, they undergo a [4 + 2] cycloaddition. In contrast to the photolysis in the absence of these carbonyl compounds, a Wolff rearrangement of 1b – d (or the derived carbenes) to silyl ketenes 5b – d is observed as a competitive reaction.

ChemInform Abstract: NiO-Al2O3 Prepared from a Ni-Al Hydrotalcite Precursor as an Efficient Catalyst for Transfer Hydrogenation Reactions.

Abstract NiO-Al2O3 catalyst prepared by calcining a Ni-Al hydrotalcite precursor efficiently reduces nitroarenes and carbonyl compounds in presence of propan-2-ol and KOH. Presence of two different reducible groups in the substrate leads to chemoselective reduction.

Zinc triflate: a highly efficient reusable catalyst in the synthesis of functionalized quinolines via Friedlander annulation

An environmentally friendly and highly efficient procedure for the preparation of quinolines and fused polycyclic quinolines has been developed by a simple Friedlander annulation reaction of 2-aminoaryl ketone with carbonyl compounds in presence of zinc triflate under microwave irradiation and solvent-free conditions. The reaction also proceeds effectively when In(OTf)(3) was used in lieu of Zn(OTf)(2) as the catalyst. The catalyst can be recovered after the reaction and reused efficiently in subsequent runs.

ChemInform Abstract: Synthesis of 1,3‐Diazapyrenes and 1,3,7‐Triazapyrenes by the Reaction of 1,8‐Naphthalenediamine with Triazine in the Presence of Carbonyl Compounds or Benzonitrile in Polyphosphoric Acid.

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Oxidation of lube-stock sulfides by hydrogen peroxide in the presence of carbonyl compounds

The oxidation of lube-stock sulfides with hydrogen peroxide in the presence of carbonyl compounds was studied, and the activity of the additives was compared in terms of the degree depth and selectivity of the conversion of sulfides into sulfoxides. It was shown that alicyclic ketones and lower aliphatic carbonyl compounds exhibit the highest activity.

Synthesis of 1,3-diazapyrenes and 1,3,7-triazapyrenes by the reaction of 1,8-naphthalenediamine with triazine in the presence of carbonyl compounds or benzonitrile in polyphosphoric acid

A novel three-component synthesis has been developed for 1,3-diazapyrenes based on the reaction of 1,8-naphthalenediamine with triazine and carbonyl compounds in polyphosphoric acid (PPA). The use of benzonitrile in place of the carbonyl compounds in this reaction gives 6-phenyl-1,3,7-triazapyrenes.