Aromatic Carbonyl Research Articles

Multi-Component One-Pot Reaction of Aromatic Carbonyl Compounds, Tosylhydrazide, and Arylboronic Acids.

In this paper, we developed a new method using 4-bromoacetophenone as the starting material, with tosylhydrazide and two arylboronic acids using Barluenga and Suzuki couplings in a four-component one-pot reaction to afford the target product 4-benzyl-1,1′-biphenyls. This system that we have developed enables the use of easily accessible starting materials and can be employed on a wide variety of substrates with good functional group tolerance. In particular, this protocol can be applied to the synthesis of 4-(1-([1,1′-biphenyl]-4-yl)ethyl)pyridine derivatives, a class of potential analogs of CPY17 inhibitors of prostate cancer.

Insights into the Cobalt-Catalyzed Three-Component Coupling of Mixed Aromatic Organozinc Species, Carbonyl Compounds or Imines and Michael Acceptors: Synthetic and Mechanistic Aspects

The first examples of cobalt-catalyzed multicomponent couplings of mixed aromatic arylzinc reagents with Michael acceptors and carbonyl compounds or imines is described. The reaction system employs a cobalt(II)-2,2′-bipyridine or a cobalt(II)-1,10-phenanthroline complex as a catalyst for both organozinc generation and subsequent multicomponent assembly by formal Michael addition/aldol coupling or Mannich reaction. This study brings new insights into the synthetic scope and mechanism of the reaction.

Process optimization of lignin conversion into value added chemicals by thermochemical pretreatment and electrooxidation on a stainless steel anode

AbstractWheat straw soda lignin was subjected to thermochemical (TC) pretreatment at low to moderate temperatures followed by electrooxidation (EO) on an SS-304 anode to produce some value-added organic chemicals. The influence of independent process variables on the product yield of major organic chemical groups, namely, aromatic carbonyl compounds (COarom), aromatic hydrocarbons (HCarom), and aliphatic hydrocarbons (HCaliph), was studied. Response surface methodology (RSM) was used to optimize the process conditions for maximizing the amount of chemical production according to the Box-Behnken experimental design (BBD). For COarom, the optimal conditions were 2 h TC pretreatment at 200°C followed by 12 h of EO at 2.24 mA cm−2current density to yield 24.7% of desired products. The optimized synthesis conditions for HCaromare 2 h TC treatment at 200°C yielding 16.1% desired products. As individual compounds, vanillin, acetosyringone, syringaldehyde, acetovanillone,o-xylene and toluene were significantly produced in different product groups. A small amount of organosilicon compounds (ORGSi) and HCaliphwas also produced.

Efficient Catalytic Hydrodeoxygenation of Aromatic Carbonyls over a Nitrogen‐Doped Hierarchical Porous Carbon Supported Nickel Catalyst

AbstractHydrodeoxgenation of ketones or aldehydes allows for efficient transformation of oxygen containing raw materials into value‐added chemicals and biofuels, which calls for efficient but inexpensive alternative catalytic systems. In the present contribution, a nitrogen‐doped hierarchical porous carbon (NHPC) was fabricated in a “leavening” method, functioning as a superior support for the anchoring of highly dispersed Ni nanoparticles (Ni/NHPC with ∼ 6.5 nm Ni nanoparticles). When tested in hydrodeoxygenation of bio‐derived vanillin (4‐hydroxy‐3‐methoxybenzaldehyde), this catalyst demonstrated much enhanced catalytic activity as compared to Ni/HPC (HPC means hierarchical porous carbon without nitrogen doping). A direct hydrogenolysis or hydrogenation‐hydrogenolysis reaction mechanism was proposed, which allows the present Ni/NHPC to exert full oxygen removal of a broad set of aromatic substrates with carbonyl or ‐OH at benzylic position. The modified electronic state of nickel interacted with nitrogen dopant and enhanced mass transfer contributed by the hierarchical porous structure of NHPC may be reasons for high reactivity.

Triplet Harvesting with a Simple Aromatic Carbonyl

AbstractThe front cover artwork is provided by the groups of Prof. Peter Gilch (HHU Düsseldorf) and Prof. Andrew Monkman (Durham University). The image shows a chimera illuminated by the fluorescence emission of thioxanthone, the aromatic carbonyl studied here. Due to singlet and triplet excitations in close energetic vicinity, its photophysics exhibits a chimeric behavior. This behavior renders the class of molecules interesting as emitters in OLEDs. Read the full text of the article at 10.1002/cphc.201700683.

The influence of mesoporous silica modified with phosphorus and nitrogen‐containing hyperbranched molecules on thermal stability, combustion behavior, and toxic volatiles of epoxy resin

A hybrid material (HPPA‐SH‐mSiO2) containing multiple flame‐retardant elements was synthesized and characterized using NMR, FTIR, and XPS techniques. This hybrid was synthesized by the “thiol–ene” click reaction of thiol‐functionalized mesoporous silica (SH‐mSiO2) with ene‐terminated hyperbranched polyphosphate acrylate (HPPA).When 2 wt% HPPA‐SH‐mSiO2 hybrid was added to an epoxy matrix, thermogravimetric analysis (TGA) showed that the incorporation of HPPA‐SH‐mSiO2 increased the thermal stability of epoxy resin composites. Moreover, the combustion behavior of epoxy composites was investigated using a cone calorimeter, and the results show that the PHRR and THR of EP/HPPA‐SH‐mSiO2 composites clearly decreased by 28.7% and 16%, respectively. Volatile toxic compounds such as aromatic compounds, CO, carbonyl compounds, and hydrocarbons were identified using TGA‐infrared spectroscopy coupling technique. The effect of HPPA‐SH‐mSiO2 hybrids on the removal of toxic volatiles was also investigated. Functionalized mesoporous silica and polymer composites have potential applications.

Triplet Harvesting with a Simple Aromatic Carbonyl

The efficiency of organic light-emitting diodes crucially depends on triplet harvesters. These accept energy from triplet correlated electron hole pairs and convert it into light. Here, experimental evidence is given that simple aromatic carbonyls, such as thioxanthone, could serve this purpose. In these compounds, the emissive 1 ππ* excitation may rapidly equilibrate with an upper triplet state (3 nπ*). This equilibrium may persist for nanoseconds. Population of the 3 nπ* state via energy transfer from an electron hole pair should result in fluorescence emission and thereby triplet harvesting. To demonstrate the effect, solutions of 1,4-dichlorobenzene (triplet sensitizer) and thioxanthone (harvester) were excited at 266 nm with a nanosecond laser. The emission decay reveals a 100 ns decay absent in the thioxanthone only sample. This matches predictions for an energy transfer limited by diffusion and gives clear evidence that thioxanthone can convert triplet excitations into light.

Influence of relative humidity on heterogeneous reactions of O3 and O3/SO2 with soot particles: Potential for environmental and health effects

The heterogeneous reactions of soot particles with O3 and the mixture of O3 and SO2 were studied as a function of relative humidities (RHs). The reactions were followed in real time using microscopic Fourier transform infrared (micro-FTIR) spectrometer to obtain kinetic data. The results show that the ketone (CO) group is the main product of the O3/soot reaction, and the sulfate is identified on the surface of soot particles in the presence of O3/SO2. Both reactions are sensitive to RHs and surrounding water significantly promotes the proceeding of the heterogeneous reactions. For the O3/soot reaction, the pseudo-first-order rate constant increases from 3.2 × 10−4 s−1 to 7.1 × 10−4 s−1 with increasing RH in the range of 1%–82%. When O3 and SO2 exist simultaneously during the reaction, the reaction rate and uptake coefficient are all enhanced by about an order of magnitude as the RH increases from 1% to 83%. The high productions of the ketone and sulfate on soot surface are of highly hydrophilic, which play a key role in environmental effect under humid environment. The possible reaction mechanism speculates that products of aromatic carbonyls and dihydrofuran species on soot particles will be more harmful to human health.

Shedding new light on an old molecule: quinophthalone displays uncommon N-to-O excited state intramolecular proton transfer (ESIPT) between photobases

Excited state dynamics of common yellow dye quinophthalone (QPH) was probed by femtosecond transient absorption spectroscopy. Multi-exponential decay of the excited state and significant change of rate constants upon deuterium substitution indicate that uncommon nitrogen-to-oxygen excited state intramolecular proton transfer (ESIPT) occurs. By performing density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations, we found that adiabatic surface crossing between the S1 and S2 states takes place in the photoreaction. Unlike most cases of ESIPT, QPH does not exhibit tautomer emission, possibly due to internal conversion or back-proton transfer. The ESIPT of QPH presents a highly interesting case also because the moieties participating in ESIPT, quinoline and aromatic carbonyl, are both traditionally considered as photobases.

Photo‐oxidation of poly(2,6‐dimethyl‐1,4‐phenylene oxide): A reinvestigation

ABSTRACTReinvestigation of poly(2,6‐dimethyl‐1,4‐phenylene oxide) photodegradation at wavelengths > 290 nm shows that both methyl groups and aromatic rings are sites of oxidation with their relative rates dependent on exposure conditions, based on infrared spectroscopy. The methyl group loss is linear with exposure and apparently proceeds by direct abstraction of a benzylic hydrogen by oxygen. The aromatic ring loss and carbonyl growth in the IR spectra appear to be auto‐accelerating and seem to proceed by electron transfer to oxygen, either sensitized or through a direct reaction with oxygen, and recombination of the polymer radical cation and superoxide to result in oxygen addition to the ring. Molecular weight loss in solution occurs to a significant degree only in the presence of oxygen, even in the presence of a hydrogen‐donating solvent, indicating that aryl ether photolysis is not a major pathway. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2318–2331

Characterization of AKR1B16, a novel mouse aldo-keto reductase

Aldo-keto reductases (AKRs) are distributed in three families and multiple subfamilies in mammals. The mouse Akr1b3 gene is clearly orthologous to human AKR1B1, both coding for aldose reductase, and their gene products show similar tissue distribution, regulation by osmotic stress and kinetic properties. In contrast, no unambiguous orthologs of human AKR1B10 and AKR1B15.1 have been identified in rodents. Although two more AKRs, AKR1B7 and AKR1B8, have been identified and characterized in mouse, none of them seems to exhibit properties similar to the human AKRs. Recently, a novel mouse AKR gene, Akr1b16, was annotated and the respective gene product, AKR1B16 (sharing 83% and 80% amino acid sequence identity with AKR1B10 and AKR1B15.1, respectively), was expressed as insoluble and inactive protein in a bacterial expression system. Here we describe the expression and purification of a soluble and enzymatically active AKR1B16 from E. coli using three chaperone systems. A structural model of AKR1B16 allowed the estimation of its active-site pocket volume, which was much wider (402 Å3) than those of AKR1B10 (279 Å3) and AKR1B15.1 (60 Å3). AKR1B16 reduced aliphatic and aromatic carbonyl compounds, using NADPH as a cofactor, with moderate or low activity (highest kcat values around 5 min−1). The best substrate for the enzyme was pyridine-3-aldehyde. AKR1B16 showed poor inhibition with classical AKR inhibitors, tolrestat being the most potent. Kinetics and inhibition properties resemble those of rat AKR1B17 but differ from those of the human enzymes. In addition, AKR1B16 catalyzed the oxidation of 17β-hydroxysteroids in a NADP+-dependent manner. These results, together with a phylogenetic analysis, suggest that mouse AKR1B16 is an ortholog of rat AKR1B17, but not of human AKR1B10 or AKR1B15.1. These human enzymes have no counterpart in the murine species, which is evidenced by forming a separate cluster in the phylogenetic tree and by their unique activity with retinaldehyde.

A pH-responsive glycolipid-like nanocarrier for optimising the time-dependent distribution of free chemical drugs in focal cells

Though Drug delivery systems have achieved accumulation at tumor sites via passive targeting and active targeting, the therapeutic effects are far from perfect. The unsatisfactory results are mainly due to limited drug release from the nanocarriers at tumor sites, while the pharmacological activities of the drug are attributed to the concentration of the free drug and the time maintained at the pharmacological targets. A pH-responsive chitosan based glycolipid-like nanocarrier (CSO-FBA-SA) was fabricated by conjugating stearyl alcohol (SA) to chitosan oligosaccharide (CSO) with the linkage of 4-formylbenzoic acid (FBA). FBA was a kind of aromatic aldehyde carbonyl compounds, which can form the benzoic-imine bond. In the presence of a Schiff’s base structure, the carrier showed improved properties and could be quickly degraded in an acidic environment. In order to explore the process and mechanism of the nanocarriers in focal cells, the method for determining the intracellular concentration of released free doxorubicin was established, and the time-dependent change of the DOX-loaded micelles was revealed. The sight of drug release was also obtained with CLSM. The cytotoxicity of the CSO-FBA-SA/DOX against human breast cancer MCF-7 cells increased by 2.75-fold and 3.77-fold in comparison with the CSO-SA/DOX and DOX, respectively. Furthermore, the CSO-FBA-SA/DOX showed a 2.12-fold higher cytotoxicity against the MCF-7 cells than that treated against human ovarian cancer SKOV-3 cells with lower intracellular pH value, which indicated that the cellular inhibition positively correlated with the intracellular pH value. High tumor accumulation and fast drug release of the CSO-FBA-SA/DOX in tumor was responsible for the remarkable tumor growth inhibitory effect. Moreover, the CSO-FBA-SA/DOX could selectively respond to the acidic environment and release DOX in tumor only, which had relatively minimal cytotoxicity towards normal tissues. The results showed that this newly developed glycolipid-like nanocarrier could act as a potential vector for delivering the drug effectively with a low systemic toxicity.

Syntheses and structural investigations of new half sandwich Ir(III) and Rh(III) amine compounds and their catalytic transfer hydrogenation of aromatic ketones and aldehydes in water

Six new compounds, [IrCp*(p-R-N-(pyridin-2-ylmethyl)aniline)Cl]PF6 (R=H (1); F (2); OCH3 (3)), and [RhCp*(p-R-N-(pyridin-2-ylmethyl)aniline)Cl]PF6 (R=H (4); F (5); OCH3 (6)), (where Cp*=pentamethylcyclopentadiene) have been synthesized. Furthermore, the new [IrCp*(N-methyl-N-(pyridin-2-ylmethyl)aniline)Cl]PF6 (7) and [RhCp*(N-methyl-N-(pyridin-2-ylmethyl)aniline)Cl]PF6 (8) compounds were synthesized to allow an investigation of the role of the NH group and NCH3 in the proposed reaction mechanism of transfer hydrogenation. The synthesized compounds were characterized by 1H NMR, 2D NMR, 13C{1H} NMR, HR-Mass spectroscopy, IR spectroscopy and elemental analysis. 1H NMR studies revealed that the N,N’ amine and NCH3 protected N,N’ bidentate ligands coordinated to the Ir(III) and Rh(III) metal ions and the compounds 1-8 exhibit diastereoisomers in DMSO-d6 solution at room temperature. Time dependent 1H NMR studies show that the Ir(III) amine compounds 1-3 are oxidized to imine complexes by molecular oxygen. The crystal structures of the complexes [Cp*IrCl(N-(pyridin-2-ylmethyl)aniline)]PF6 (1) and [Cp*RhCl(p-OCH3-N-(pyridin-2-ylmethyl)aniline)]PF6 (6) have been resolved by single crystal X-ray diffraction. The Ir(III) and Rh(III) amine compounds were compared in the catalytic transfer hydrogenation reaction. The Rh(III) amine and imine compounds were found to be more versatile than the Ir(III) amine and imine compounds. Thus, the Rh(III) compounds were particularly effective for the catalytic transfer hydrogenation of aromatic carbonyl groups in water with sodium formate and formic acid as the hydrogen source under pH dependent acidic conditions. The higher activation of compounds 1–3 vs 7 and 4–6 vs 8 supports a dominant mechanism in which the NH moiety contributes to the activation of the carbonyl compounds. Furthermore, the Rh(III) amine catalyst (4) can be easily recovered from the reaction medium and reused for at least three catalytic cycles without decrease in conversions.

Phosphorescence in Bromobenzaldehyde Can Be Enhanced through Intramolecular Heavy Atom Effect

A synthetic route to achieve high phosphorescence quantum yield in a purely organic material was achieved by doping a crystal containing heavy bromine atoms with a molecule that contains a triplet producing aromatic carbonyl group. The enhanced phosphorescence originated from intermolecular nonbonding interactions between the bromine and the carbonyl oxygen. In this study we employ a computational approach to design molecules containing both structural motifs, which exhibit enhanced phosphorescence through intramolecular nonbonding interactions between bromine and carbonyl groups.

Enhanced Thermally Activated Delayed Fluorescence in New Fluorescein Derivatives By Introducing Aromatic Carbonyl Groups

AbstractIn this work, two new fluorescein derivatives which exhibit thermally activated delayed fluorescence (TADF) were rationally designed and synthesized by introducing aromatic carbonyl groups to increase the rate of intersystem crossing. The TADF properties of one of two compounds (the thiophene‐containing derivative) were found to be additionally enhanced as a result of the presence of the thiophene moieties, with the compound having a TADF lifetime of 52.05 μs in deaerated ethanol. The thiophene‐containing derivative was used in time‐resolved luminescence imaging of MCF‐7 cells.

Chemical characterization of diesel and hydrotreated vegetable oil (HVO) soot after reactive gas probing using diffuse reflectance FTIR spectroscopy (DRIFTS).

A chemical characterization of diesel and hydrotreated vegetable oil (HVO) soot has been developed using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) before and after the reaction with different probe gases. Samples were generated under combustion conditions corresponding to an urban operation mode of a diesel engine and were reacted with probe gas-phase molecules in a Knudsen flow reactor. Specifically, NH2OH, O3 and NO2 were used as reactants (probes) and selected according to their reactivities towards specific functional groups on the sample surface. Samples of previously ground soot were diluted with KBr and were introduced in a DRIFTS accessory. A comparison between unreacted and reacted soot samples was made in order to establish chemical changes on the soot surface upon reaction. It was concluded that the interface of diesel and HVO soot before reaction mainly consists polycyclic aromatic hydrocarbons, nitro and carbonyl compounds, as well as ether functionalities. The main difference between both soot samples was observed in the band of the C=O groups that in diesel soot was observed at 1719 cm-1 but not in HVO soot. After reaction with probe gases, it was found that nitro compounds remain on the soot surface, that the degree of unsaturation decreases for reacted samples, and that new spectral bands such as hydroxyl groups are observed.

Rapid and efficient one-pot microwave-assisted synthesis of 2-phenylimidazo[1,2-a]pyridines and 2-phenylimidazo[1,2-a]quinoline in water–PEG-400

ABSTRACTAn effective, expeditious, environmentally benign one-pot synthesis of 2-phenylimidazo[1,2-a]pyridines and 2-phenylimidazo[1,2-a]quinoline from easily available starting materials as aromatic carbonyl compound, 2-amino pyridine, succinamide, and in situ generated α-iodo acetophenone in combination with green solvent PEG-400 and water (2:1) under microwave irradiation. The newly developed protocol with excellent yield of product in very short time of reaction by avoiding the use of lachrymatric α-chloro and α-bromocarbonyl compounds, volatile, toxic organic and hazardous solvents, reagents is the advantage of this research work. The final products were confirmed by their characterization data such as 1H NMR, 13C NMR, high resolution mass spectrometry (HRMS) and were compared with its reported method.

The influence of hydrogen bonding on partition coefficients.

This Perspective explores how consideration of hydrogen bonding can be used to both predict and better understand partition coefficients. It is shown how polarity of both compounds and substructures can be estimated from measured alkane/water partition coefficients. When polarity is defined in this manner, hydrogen bond donors are typically less polar than hydrogen bond acceptors. Analysis of alkane/water partition coefficients in conjunction with molecular electrostatic potential calculations suggests that aromatic chloro substituents may be less lipophilic than is generally believed and that some of the effect of chloro-substitution stems from making the aromatic π-cloud less available to hydrogen bond donors. Relationships between polarity and calculated hydrogen bond basicity are derived for aromatic nitrogen and carbonyl oxygen. Aligned hydrogen bond acceptors appear to present special challenges for prediction of alkane/water partition coefficients and this may reflect 'frustration' of solvation resulting from overlapping hydration spheres. It is also shown how calculated hydrogen bond basicity can be used to model the effect of aromatic aza-substitution on octanol/water partition coefficients.

Laser photolysis studies of ω-bond dissociation in aromatic carbonyls with a C-C triple bond stimulated by triplet sensitization.

We have prepared three types of carbonyl compounds, benzoylethynylmethyl phenyl sulfide (2@SPh), (p-benzoyl)phenylethynylmethyl phenyl sulfide (3@SPh) and p-(benzoylethynyl)benzyl phenyl sulfide (4@SPh) with benzoyl and phenylthiylmethyl groups, which are interconnected with a C-C triple bond and a phenyl ring. Laser flash photolysis of 3@SPh and 4@SPh in acetonitrile provided the transient absorption spectra of the corresponding triplet states where no chemical reactions were recognized. Upon laser flash photolysis of 2@SPh, the absorption band due to the phenylthiyl radical (PTR) was obtained, indicating that the C-S bond cleaved in the excited state. Triplet sensitization of these carbonyl compounds using acetone and xanthone was conducted using laser photolysis techniques. The formation of triplet 3@SPh was seen in the transient absorption, whereas the PTR formation was observed for 2@SPh and 4@SPh, indicating that the triplet states were reactive for the C-S bond dissociation. The C-S bond dissociation mechanism for 4@SPh upon triplet sensitization is discussed in comparison with those for 2@SPh and 3@SPh.

Feasibility of Room Temperature Reduction of Aromatic Carbonyl and Nitro Compounds by Zn/dil. HCl-Et2O System: An Experimental and DFT Study

Feasibility of Room Temperature Reduction of Aromatic Carbonyl and Nitro Compounds by Zn/dil. HCl-Et2O System: An Experimental and DFT Study