Aromatic Carbonyl Research Articles

2-(2-Hydroxyphenyl)imidazolidines and their O-phosphorylated derivatives

2-(2-Hydroxyaryl)imidazolidines were synthesized by reaction of aromatic carbonyl compounds with N,N′-dialkylethylenediamines. The title compounds were also prepared using the corresponding Schiff bases instead of carbonyl compounds. Phosphorylation of 2-(2-hydroxyphenyl)imidazolidines with phosphoryl and phosphorothioyl chlorides and phosphorochloridites was accomplished. The reaction of O-phosphorylsalicylaldehyde with N,N′-dialkylethylenediamines also afforded 2-(2-hydroxyphenyl)imidazolidines.

Kinematic anharmonicity of internal rotation of molecules

The methods of analysis the strongly coupled vibrations are proposed for a number of molecules of aromatic and heterocyclic carbonyl (and some others) compounds. The qualitative principles are formulated for molecular systems with a significant kinematic anharmonicity.

A Green Approach for Allylations of Aldehydes and Ketones: Combining Allylborate, Mechanochemistry and Lanthanide Catalyst.

Secondary and tertiary alcohols synthesized via allylation of aldehydes and ketones are important compounds in bioactive natural products and industry, including pharmaceuticals. Development of a mechanochemical method using potassium allyltrifluoroborate salt and water, to successfully perform the allylation of aromatic and aliphatic carbonyl compounds is reported for the first time. By controlling the grinding parameters, the methodology can be selective, namely, very efficient for aldehydes and ineffective for ketones, but by employing lanthanide catalysts, the reactions with ketones can become practically quantitative. The catalyzed reactions can also be performed under mild aqueous stirring conditions. Considering the allylation agent and its by-products, aqueous media, energy efficiency and use of catalyst, the methodology meets most of the green chemistry principles.

To Photoredox or Not in Neutral Aqueous Solutions for Selected Benzophenone and Anthraquinone Derivatives.

The experimental and theoretical results in neutral aqueous solutions reported here indicate that a proton-coupled electron transfer (PCET) from an alcohol C-H bond to the para-carbonyl is the initial and crucial process for the photoredox reaction of 2-(1-hydroxyethyl)-anthraquinone (HEAQ) to occur while the counterpart 3-(hydroxymethyl)-benzophenone (3-BPOH) compound displays a different PCET from an alcohol O-H bond to the carbonyl as the first step, followed by an intersystem crossing process that does not lead to the analogous photoredox, which is caused by a subtle charge-radical coupled effect between HEAQ and 3-BPOH. This can account for experimental results in the literature that HEAQ can undergo efficient photoredox but 3-BPOH does not under neutral aqueous conditions. These results have implications for the pH-dependent photochemical behavior of aromatic carbonyl compounds in aqueous media.

ChemInform Abstract: Room‐Temperature Phosphorescence from Purely Organic Materials

AbstractReview: [41 refs.

Taking on an organic glow

Phosphorescent materials, which continue to glow even after the light that put them into an excited state has been removed, have applications in electronics, optics, and biology. But achieving phosphorescence at room temperature and in the presence of oxygen can be tough because the excited state of such molecules is sensitive to these conditions. To date, most compounds that exhibit room-temperature phosphorescence contain metals, making them more costly and potentially toxic. Chemists in China now report a series of five organic molecules that efficiently and persistently phosphoresce in a range of colors in air and at room temperature (Chem 2016, DOI: 10.1016/j.chempr.2016.08.010). The team, led by Ben Zhong Tang of Hong Kong University of Science & Technology and Qian Peng of the Institute of Chemistry, Chinese Academy of Sciences, designed the aromatic carbonyl compounds so that their excited states have a tunable configuration that promotes phosphorescence. The most promising compound,

Competition between “Meta Effect” Photochemical Reactions of Selected Benzophenone Compounds Having Two Different Substituents at Meta Positions

Recent studies conducted on some "meta effect" photochemical reactions focused on aromatic carbonyls having a substitution on one meta position of the benzophenone (BP) and anthraquinone parent compound. In this paper, two different substitutions were introduced with one at each meta position of the BP parent compound to investigate possible competition between different types of meta effect photochemistry observed in acidic solutions containing water. The photochemical pathways of 3-hydroxymethyl-3'-fluorobenzophenone (1) and 3-fluoro-3'-methylbenzophenone (2) were explored in several solvents, including acidic water-containing solutions, using time-resolved spectroscopic experiments and density functional theory computations. It is observed that 1 can undergo a photoredox reaction and 2 can undergo a meta-methyl deprotonation reaction in acidic water-containing solutions. Comparison of these results to those previously reported for the analogous BP derivatives that contain only one substituent at a meta position indicates the introduction of electron-donating (such as hydroxyl) and electron-withdrawing groups (such as F) on the meta positions of BP can influence the meta effect photochemical reactions. It was found that involvement of an electron-donating moiety facilitates the meta effect photochemical reactions by stabilizing the crucial reactive biradical intermediate associated with the meta effect photochemical reactions.

Indium triflate promoted one-pot multicomponent synthesis of structurally diverse 3-amino-imidazo[1,2-a]pyridines.

An efficient, mild, and expeditious synthetic protocol has been developed for the synthesis of structurally diverse 3-amino-imidazo[1,2-a]pyridines, involving a three-component, one-pot cyclocondensation reaction of 2-aminobenzothiazole/2-aminoazines, ethyl isocyanoacetate/tert-butyl isocyanides, and pyrazole-3(4)-carbaldehyde/substituted aromatic carbonyl compounds in 45min. using In(OTf)[Formula: see text] as a catalyst in toluene. Mild reaction conditions, high atom economy, operational simplicity, short reaction time, and structural diversity with high product conversion are among the advantages of the present synthetic protocol.

An investigation of accelerated temperature-induced ageing of four wood species: colour and FTIR

The study investigated and compared the behaviour of four wood species, originating from Europe and China, in terms of temperature-induced artificial ageing. It was conducted at 100 °C for a total period of 288 h. Ageing effects were evaluated by colour measurements in the CIE Lab system and by FTIR analysis. Colour changes were then related to chemical changes in the wood. The investigated wood species were European ash (Fraxinus excelsior), European walnut (Juglans regia), Chinese ash (Fraxinus mandshurica) and Chinese walnut (Juglans mandshurica). Colour changes were maximum for European ash and minimum for Chinese ash, while European walnut and Chinese walnut evolved quite similarly. Main chemical changes due to temperature ageing were reduction of hydroxyl groups, increase of the unconjugated carbonyl groups and an apparent slight increase of lignin, more evident for European ash and delayed for European walnut. Formation of aromatic carbonyl conjugated groups as quinoid structures as a result of oxidative reactions was revealed especially for European ash. The different behaviour of the studied wood species may be explained by their different chemical composition, especially hemicelluloses, lignin and extractives content.

Paternò–Büchi photochemical [2 + 2] cycloaddition of aromatic carbonyl compounds with 2‐siloxy‐1H‐pyrrole derivatives

The purpose of this study was to explore regioselectivity and stereoselectivity in the Paternò–Büchi reaction of pyrrole derivatives. The regioselective formation of a bicyclic oxetane in the Paternò–Büchi reaction of 2‐siloxypyrrole with benzophenone was reported for the first time, and a mechanism involving the distribution of the intermediary triplet diradicals was proposed to account for the regioselectivity of the reaction. Copyright © 2016 John Wiley & Sons, Ltd.

Deoxygenative silylation of aromatic carbonyl compounds with HSiCl3 in the presence of quaternary phosphonium chloride: A facile route to arylmethyltrichlorosilane

Aromatic carbonyl compounds such as aromatic aldehydes and ketones [R1R2CO: R1=H; R2=Ph (1a), 2,4-Cl2Ph (1b), 2,4-Me2Ph (1c): R1=Ph; R2=Ph (1d), 4-ClPh (1e), 4-MePh (2f), 2,4-Me2Ph (1g) undergo the deoxygenative silylation with HSiCl3 in the presence of Bu4PCl at 150°C within 1.0–1.5h to give arylmethyltrichlorosilanes 2 (R1R2CH–SiCl3) in high yields (85–95%). The reactivity of aromatic carbonyl compounds decreases with increasing the electron withdrawing ability of substituent(s) on the benzene-ring. A highly efficient synthetic route to arylmethyltrichlorosilanes has been developed starting from aromatic aldehydes and ketones in this study.

Iron-Catalyzed Ortho C-H Methylation of Aromatics Bearing a Simple Carbonyl Group with Methylaluminum and Tridentate Phosphine Ligand.

Iron-catalyzed C-H functionalization of aromatics has attracted widespread attention from chemists in recent years, while the requirement of an elaborate directing group on the substrate has so far hampered the use of simple aromatic carbonyl compounds such as benzoic acid and ketones, much reducing its synthetic utility. We describe here a combination of a mildly reactive methylaluminum reagent and a new tridentate phosphine ligand for metal catalysis, 4-(bis(2-(diphenylphosphanyl)phenyl)phosphanyl)-N,N-dimethylaniline (Me2N-TP), that allows us to convert an ortho C-H bond to a C-CH3 bond in aromatics and heteroaromatics bearing simple carbonyl groups under mild oxidative conditions. The reaction is powerful enough to methylate all four ortho C-H bonds in benzophenone. The reaction tolerates a variety of functional groups, such as boronic ester, halide, sulfide, heterocycles, and enolizable ketones.

ChemInform Abstract: Photochemical Electron and Hydrogen Transfer in Organic Synthesis: The Control of Selectivity

AbstractReview: [112 refs.

Chemical constituents of tobacco smoke induce the production of interleukin-8 in human bronchial epithelium, 16HBE cells.

BackgroundInterleukin-8 (IL-8) functions as a major chemoattractant and plays pivotal roles in the initiation and development of chronic obstructive pulmonary disease (COPD), and tobacco smoke is a most risk factor contributing to the development of COPD. Hence, we have screened some of the tobacco smoke-derived chemical compounds that potentially induce the production of IL-8 in human bronchial epithelium, 16HBE cells.MethodsTwenty-eight hazardous smoke components belonging to 9 classes including nicotine, ammonia, aromatic amines, polycyclic aromatic hydrocarbons, phenols, carbonyls, hydrocyanic acid, nitrosamines and other volatile organics were used in the experiments. Proliferation of 16HBE cells was determined by cell counting kit-8 kit, luciferase activity was measured in IL-8 reporter gene-expressing 16HBE cells, and IL-8 levels in culture supernatants were quantified by enzyme-linked immunosorbent assay.ResultsAt the non-toxic dosages, chemical compounds belonging to nicotine, aromatic amines, benzopyrene, phenols, aldehydes, and some other volatile organics dose-dependently increased IL-8 reporter gene expression. Consistently, the representative compounds belonging to nicotine, aromatic amines, benzopyrene, phenols, aldehydes, and some other volatile organics significantly and dose-dependently increased IL-8 levels in the culture supernatants of 16HBE cells, among these compounds, benzopyrene is a most potent stimulator for inducing IL-8 production.ConclusionsThe present study has identified particular tobacco smoke constituents responsible for inducing the IL-8 production in human bronchial epithelium, which might help shed light on the pathogenesis of tobacco smoke-induced COPD.

Room-temperature phosphorescence from purely organic materials

Abstract Room-temperature phosphorescence (RTP) materials have attracted great attention due to their involvement of excited triplet states and comparatively long decay lifetimes. In this short review, recent progress on enhancement of RTP from purely organic materials is summarized. According to the mechanism of phosphorescence emission, two principles are discussed to construct efficient RTP materials: one is promoting intersystem crossing (ISC) efficiency by using aromatic carbonyl, heavy-atom, or/and heterocycle/heteroatom containing compounds; the other is suppressing intramolecular motion and intermolecular collision which can quench excited triplet states, including embedding phosphors into polymers and packing them tightly in crystals. With aforementioned strategies, RTP from purely organic materials was achieved both in fluid and rigid media.

Ketyl Radical Formation via Proton-Coupled Electron Transfer in an Aqueous Solution versus Hydrogen Atom Transfer in Isopropanol after Photoexcitation of Aromatic Carbonyl Compounds.

The excited nπ* and ππ* triplets of two benzophenone (BP) and two anthraquinone (AQ) derivatives have been observed in acetonitrile, isopropanol, and mixed aqueous solutions using time-resolved resonance Raman spectroscopic and nanosecond transient absorption experiments. These experimental results, combined with results from density functional theory calculations, reveal the effects of solvent and substituents on the properties, relative energies, and chemical reactivities of the nπ* and ππ* triplets. The triplet nπ* configuration was found to act as the reactive species for a subsequent hydrogen atom transfer reaction to produce a ketyl radical intermediate in the isopropanol solvent, while the triplet ππ* undergoes a proton-coupled electron transfer (PCET) in aqueous solutions to produce a ketyl radical intermediate. This PCET reaction, which occurs via a concerted proton transfer (to the excited carbonyl group) and electron transfer (to the excited phenyl ring), can account for the experimental observation by several different research groups over the past 40 years of the formation of ketyl radicals after photolysis of a number of BP and AQ derivatives in aqueous solutions, although water is considered to be a relatively "inert" hydrogen-donor solvent.

The diastereoselectivity of the Paternò-Büchi reaction between 2,3-dihydrofuran and aromatic carbonyl compounds in organized medium

Abstract The Paterno-Buchi reaction between benzaldehyde and 2,3-dihydrofuran can be performed within the cavity of NaY zeolite. An increased stereoselectivity has been observed. When the reaction was performed with substituted benzaldehyde derivatives, different stereoselectivity has been observed. The stereoselectivity can be understood assuming an interaction in the biradical intermediate between the HSOMO and the LSOMO.

Photochemical Electron and Hydrogen Transfer in Organic Synthesis: The Control of Selectivity

Two mechanisms of hydrogen transfer are often observed in photochemical reactions. In a one-step procedure, the electron and the proton are simultaneously transferred (concerted process). In a two-step procedure, first an electron is transferred and the proton follows. Such steps are observed in photochemically induced radical reactions with α,β-unsaturated carbonyl and carboxyl compounds in which a radical species is added at either the α- or the β-position. Both mechanistic steps are also observed in photochemical reactions of imides. In Norrish­–Yang-type reactions, especially with aromatic carbonyl compounds, the spin multiplicity has an influence on the resulting cycloadditions. Such reactions are interesting tools for the synthesis of natural products and for diversity-oriented synthesis. Photochemically induced hydrogen transfer in photoredox catalytic reactions is discussed in connection with proton-coupled electron transfer. 1 Introduction 2 Two Mechanisms of Hydrogen Transfer in Competition 3 Further Reactions of Interest for Application to Synthetic Organic Chemistry 4 Photochemical Keto–Enol Tautomerization 5 Electron and Hydrogen Transfer in Photoredox Catalytic Reactions 6 Conclusion

Molecular transformations of phenolic SOA during photochemical aging in the aqueous phase: competition among oligomerization, functionalization, and fragmentation

Abstract. Organic aerosol is formed and transformed in atmospheric aqueous phases (e.g., cloud and fog droplets and deliquesced airborne particles containing small amounts of water) through a multitude of chemical reactions. Understanding these reactions is important for a predictive understanding of atmospheric aging of aerosols and their impacts on climate, air quality, and human health. In this study, we investigate the chemical evolution of aqueous secondary organic aerosol (aqSOA) formed during reactions of phenolic compounds with two oxidants – the triplet excited state of an aromatic carbonyl (3C∗) and hydroxyl radical (•OH). Changes in the molecular composition of aqSOA as a function of aging time are characterized using an offline nanospray desorption electrospray ionization mass spectrometer (nano-DESI MS) whereas the real-time evolution of SOA mass, elemental ratios, and average carbon oxidation state (OSC) are monitored using an online aerosol mass spectrometer (AMS). Our results indicate that oligomerization is an important aqueous reaction pathway for phenols, especially during the initial stage of photooxidation equivalent to ∼ 2 h irradiation under midday winter solstice sunlight in Northern California. At later reaction times functionalization (i.e., adding polar oxygenated functional groups to the molecule) and fragmentation (i.e., breaking of covalent bonds) become more important processes, forming a large variety of functionalized aromatic and open-ring products with higher OSC values. Fragmentation reactions eventually dominate the photochemical evolution of phenolic aqSOA, forming a large number of highly oxygenated ring-opening molecules with carbon numbers (nC) below 6. The average nC of phenolic aqSOA decreases while average OSC increases over the course of photochemical aging. In addition, the saturation vapor pressures (C∗) of dozens of the most abundant phenolic aqSOA molecules are estimated. A wide range of C∗ values is observed, varying from < 10−20 µg m−3 for functionalized phenolic oligomers to > 10 µg m−3 for small open-ring species. The detection of abundant extremely low-volatile organic compounds (ELVOC) indicates that aqueous reactions of phenolic compounds are likely an important source of ELVOC in the atmosphere.

Synthesis and antimicrobial evaluation of hydrazones derived from 4-methylbenzenesulfonohydrazide in aqueous medium

A series of biologically active N′-substituted-4-methylbenzenesulfonohydrazide derivatives were synthesized by condensation of 4-methylbenzenesulfonohydrazide and aromatic carbonyl compounds in the presence of polystyrene sulfonic acid in aqueous medium. The synthesized compounds were characterized by IR, NMR and mass spectra. The compounds have been evaluated for antimycobacterial, antibacterial and antifungal activities.