Aromatic Olefins Research Articles

Green and Efficient: Iron-Catalyzed Selective Oxidation of Olefins to Carbonyls with O2.

A mild and operationally simple iron-catalyzed protocol for the selective aerobic oxidation of aromatic olefins to carbonyl compounds is described. Catalyzed by a Fe(III) species bearing a pyridine bisimidazoline ligand at 1 atm of O2, α- and β-substituted styrenes were cleaved to afford benzaldehydes and aromatic ketones generally in high yields with excellent chemoselectivity and very good functional group tolerance, including those containing radical-sensitive groups. With α-halo-substituted styrenes, the oxidation took place with concomitant halide migration to afford α-halo acetophenones. Various observations have been made, pointing to a mechanism in which both molecular oxygen and the olefinic substrate coordinate to the iron center, leading to the formation of a dioxetane intermediate, which collapses to give the carbonyl product.

ChemInform Abstract: Metal‐Free Protocol for the Synthesis of α‐Bromo Ketones from Olefins Using TsNBr2.

AbstractThis simple protocol allows the efficient conversion of aromatic and aliphatic olefins into α‐bromo ketones in short reaction times.

ChemInform Abstract: Metal‐Free Three‐Component Oxyazidation of Alkenes with Trimethylsilyl Azide and N‐Hydroxyphthalimide.

A novel and facile oxyazidation of alkenes under metal-free and mild conditions has been reported. A remarkable feature of the developed procedure is consecutive construction of C-O and C-N bonds in one step. The process allows quick and selective assembly of alkyl azide from readily available starting materials, where N-hydroxyphthalimide was used as an oxygen-radical precursor and TMSN3 as the N3 source. A range of aromatic alkenes bearing synthetically useful functional groups was tolerated.

ChemInform Abstract: NbCl5‐Mediated Amidation of Olefins with Nitriles to Secondary Amides.

AbstractA wide range of aliphatic, aromatic, and cyclic olefins, and aliphatic and aromatic nitriles are used.

PVC–activated carbon based matrices: A promising combination for pervaporation membranes useful for aromatic–alkane separations

The separation of aromatic–aliphatic liquid mixtures is difficult perform in a satisfactory technico-economic manner by conventional methods, such as extractive distillation, azeotropic distillation, or liquid–liquid extraction. The separation by pervaporation (PV) of liquid toluene–heptane mixtures, selected as a model mixture, was performed with several dense membranes based on poly(vinylchloride) (PVC) as the starting material. Aiming to improve the performances of pure PVC films, i.e. high selectivity and very low flux, composite membranes were prepared by incorporating different percentages of activated carbon introduced as selective sorbent fillers for toluene. In this study, we report the results obtained with composite PVC membranes containing up to 40wt% Maxsorb SPD30. The transport properties of these membranes were characterized by measurements of isothermal sorption and by pervaporation of binary mixtures. It was found that the performances of certain composite membranes were significantly increased compared with pure PVC membranes. Under the same experimental conditions, the pervaporation toluene flux was seven times higher, whereas the toluene selectivity was only slightly decreased (the permeate enrichment decreased from 89 to 83wt% at 74°C). Thus, the combination PVC with activated carbon appears to be a promising method to obtain effective PV membranes for aromatic–alkane separations.

ChemInform Abstract: Synthesis of α‐CF3 Ketones from Alkenes and Electrophilic Trifluoromethylating Reagents by Visible‐Light Driven Photoredox Catalysis.

AbstractTen α‐trifluoromethyl ketones of type (III) are prepared from aromatic alkenes (I) and Togni′s reagent (II) in a visible light‐catalyzed photoredox trifluoromethylation reaction.

ChemInform Abstract: Chiral Counteranion Strategy for Asymmetric Oxidative C(sp3)—H/C(sp3)—H Coupling: Enantioselective α‐Allylation of Aldehydes with Terminal Alkenes.

The first enantioselective α-allylation of aldehydes with terminal alkenes has been realized by combining asymmetric counteranion catalysis and palladium-catalyzed allylic C-H activation. This method can tolerate a wide scope of α-branched aromatic aldehydes and terminal alkenes, thus affording allylation products in high yields and with good to excellent levels of enantioselectivity. Importantly, the findings suggest a new strategy for the future creation of enantioselective C-H/C-H coupling reactions.

A frank synthesis of alkyl–aryl ethers from 2-halobenzaldehydes and aromatic olefins without transition metal co-catalyst and ligand

An efficient synthesis of alkyl ethers has been developed for o-deactivated aryl halides and 1-halotetralenes. The method shows good regioselectivity towards ortho substituted halides. Alkali metal carbonates (Li2CO3/Na2CO3/K2CO3/Cs2CO3) have been used without a transition metal co-catalyst and ligand. The method is simple, straight-forward and proceeds to afford products in good isolated yields. The method holds potential for future applications in organic synthesis.

ChemInform Abstract: Radical Based Strategy Toward the Synthesis of 2,3‐Dihydrofurans from Aryl Ketones and Aromatic Olefins.

AbstractThe facile protocol allows the copper‐catalyzed annulation of aryl ketones with aromatic olefins to produce a wide variety of dihydrofurans.

A convenient method for palladium-catalyzed reductive deuteration of organic substrates using deuterated hypophosphite in D2O.

A convenient method for the deuteration of organic substrates using deuterated hypophosphite as the deuterium source was investigated. Transfer deuteration of organic substrates, such as aromatic halides, alkenes, alkynes, epoxides, and O-benzyl derivatives, in the presence of palladium on carbon in deuterium oxide proceeded efficiently to give the corresponding deuterated products in excellent yields with high deuterium contents.

Epoxidation of alkenes efficiently catalyzed by Mo salen supported on surface-modified halloysite nanotubes

Halloysite-nanotube-supported Mo salen (HNTs-Mo-SL) catalysts were successfully prepared using a facile chemical surface modification and self-assembly method. The morphologies, sizes, structure, and dispersion of the as-prepared catalysts were investigated by transmission electron microscopy, X-ray diffraction, and Fourier-transform infrared, inductively coupled plasma, and X-ray photoelectron spectroscopy, which confirmed the existence of the Mo salen structure and successful synthesis of the HNTs-Mo-SL catalyst. The immobilized catalyst was found to be highly reactive in the epoxidation of a wide range of alkenes, including linear, cyclic, and aromatic alkenes. The immobilized catalyst exhibited a higher catalytic activity for alkene epoxidation than homogeneous Mo. In contrast experiments, it was determined that the salen structure played an important role in immobilizing MoO(O2)2(DMF)2 and improving the conversion and efficiency of alkene epoxidation, which could not be obtained using other ligands, such as the N atom as a single ligand. Furthermore, the bonding between Mo and the salen ligands and the possible mechanism of alkene epoxidation catalyzed by the catalyst were determined. The catalyst could be reused several times without significant loss of catalytic activity. Given that halloysite nanotubes are cheap and easy to obtain, this catalyst offers a novel alternative for the rational design of catalysts with desired features.

Pollution Characteristic of VOCs during Straw Burning Period in Chengdu, China

Volatile organic compounds (VOCs) were analyzed in straw burning period and non-straw burning period in the center of Chengdu city. The results showed that the concentrations of TVOC during straw burning were significantly higher than that in the non-straw burning period in Chengdu. The main components were alkanes, aromatic hydrocarbons and esters in straw burning period while aromatic hydrocarbons, alkanes, esters, aldehydes and ketones as the main contents in the period of non-straw burning. The correlation of TVOC, SO2, NO2, PM10, PM2.5, CO, O3 and the API index was discussed and the NOX-sensitive of photochemical reaction type was determined by the ratio of TVOC / NO2 during straw burning period.

ChemInform Abstract: Clay‐Supported Copper Nitrate (Claycop): A Mild Reagent for the Selective Nitration of Aromatic Olefins.

AbstractThe method is environmentally benign.

Rhodium-catalyzed oxidative decarbonylative Heck-type coupling of aromatic aldehydes with terminal alkenes

A rhodium-catalyzed oxidative decarbonylative Heck-type coupling of aromatic aldehydes and terminal alkenes to afford 1,2-disubstituted alkenes with good regio- and E-selectivity is developed.

ChemInform Abstract: anti‐Markovnikov Hydroamination of Aromatic Alkenes with Secondary Amines Catalyzed by Easily Accessible Yttrium Complexes.

Binaphthylamido alkyl yttrium complexes have been proven to promote the anti-Markovnikov addition between various styrene derivatives and secondary amines efficiently. Although the reaction has to be performed at high temperature, it is realized advantageously with a 1:2 amine/alkene molar ratio to deliver the hydroamination product in a satisfactory isolated yield. Furthermore, the reaction with 2-vinylpyridine proceeds at room temperature within a few minutes with a low catalyst loading of 1 mol %. The procedure has been extended to a tandem intermolecular anti-Markovnikov–intramolecular Markovnikov hydroamination for which the chiral precatalyst delivered the targeted product in up to 85 % yield and 48 % enantiomeric excess.

Metal-free three-component oxyazidation of alkenes with trimethylsilyl azide and N-hydroxyphthalimide.

A novel and facile oxyazidation of alkenes under metal-free and mild conditions has been reported. A remarkable feature of the developed procedure is consecutive construction of C-O and C-N bonds in one step. The process allows quick and selective assembly of alkyl azide from readily available starting materials, where N-hydroxyphthalimide was used as an oxygen-radical precursor and TMSN3 as the N3 source. A range of aromatic alkenes bearing synthetically useful functional groups was tolerated.

ChemInform Abstract: Combining Photoredox‐Catalyzed Trifluoromethylation and Oxidation with DMSO: Facile Synthesis of α‐Trifluoromethylated Ketones from Aromatic Alkenes.

Trifluoromethylated ketones are useful building blocks for organic compounds with a trifluoromethyl group. A new and facile synthesis of ketones with a trifluoromethyl substituent in the α-position proceeds through a one-pot photoredox-catalyzed trifluoromethylation-oxidation sequence of aromatic alkenes. Dimethyl sulfoxide (DMSO) serves as a key and mild oxidant under these photocatalytic conditions. Furthermore, an iridium photocatalyst, fac[Ir(ppy)3 ] (ppy=2-phenylpyridine), turned out to be crucial for the present photoredox process.

Selective Aryl α‐Diimine/Palladium‐Catalyzed Bis‐Alkoxy‐ carbonylation of Olefins for the Synthesis of Substituted Succinic Diesters

AbstractAryl α‐diimine derivatives have been used, for the first time, as efficient new ligands for the palladium‐catalyzed oxidative bis‐alkoxycarbonylation reaction of olefins. The most active catalyst was formed in situ from bis(9‐anthryl)‐2,3‐dimethyl‐1,4‐diazabutadiene and palladium(II) trifluoroacetate [Pd(TFA)2]. This catalytic system was able to selectively convert olefins into succinic diesters in good yields (up to 97%) and low catalyst loading (up to 0.5 mol%) under mild reaction conditions [4 bar of carbon monoxide (CO) at 20 °C in the presence of p‐toluenesulphonic acid as additive and p‐benzoquinone as oxidant]. The optimized conditions could be successfully applied to both aromatic and aliphatic olefins, by using methanol, benzyl alcohol or isopropyl alcohol as nucleophiles.magnified image

Emission of odorous volatile organic compounds from a municipal manure treatment plant and their removal using a biotrickling filter

Odorous volatile organic compounds (VOCs) from municipal manure treatment facilities are considered as a major nuisance issue for operators and nearby residents. In this study, up to 71 odorous VOCs were detected by gas chromatography–mass spectrometry at the manure treatment plant. These compounds can be classified into five different categories, including alkanes, olefins, aromatics, volatile organosulphur compounds and terpenes. Toluene, dimethyl disulphide, dimethyl sulphide, xylene and ethylbenzene were the five most abundant pollutants. A pilot-scale biotrickling filter (BTF) was employed to treat the complex odorous gases. Correlation analysis showed that the removal efficiency (RE) of the BTF was related with the molecular weight and chemical structure of contaminants. Higher than 85% of REs could be reached for aromatic, terpenes and most alkanes compounds after 180 days of operation. Comparatively, most olefins and partial alkanes compounds with a molecular weight lower than 70 were not removed easily. The REs of these compounds ranged from 0% to 94%, and the average removal efficiency (RE) was only about 33.3%.

NbCl5-mediated amidation of olefins with nitriles to secondary amides

NbCl5-mediated amidation of olefins with nitriles was successfully achieved. Various aliphatic, cyclic, and aromatic olefins, and various aliphatic and aromatic nitriles were used in this reaction to give secondary amides in high yields.