Olefins In Presence Research Articles

Twofold Carbon–Carbon Bond Formation by Intra‐ and Intermolecular Radical Reactions of Aryl Diazonium Salts

Cascade reactions: A variety of novel cascade reactions can be performed when the known and well-studied radical 5- or 6-exo-cyclization of an aryl diazonium salt is conducted in the presence of alkenes and further optional scavengers (see scheme).

Synthesis, Molecular Docking Studies and Antibacterial Evaluation of Baylis-Hillman Adducts of Coumarin and Pyran Derivatives Using Ionic Liquid under Microwave Irradiation

The Baylis-Hillman adducts 3(a-e) and 6(a-g) were prepared by the reaction of appropriate aldehydes with alkenes in presence of catalytic amount of urotropine with ionic liquids under microwave irradiation. Structures of the newly synthesized compounds were characterized by spectral studies. The antibacterial studies of Baylis-Hilmann compounds for analysis of the structural requirements for antibacterial activity using VLife MDS 3.5 has been carried out.

ChemInform Abstract: Gold—Alkene Complexes

AbstractReview: 90 refs.

Expanding the Scope of Donor/Acceptor Carbenes to N-Phthalimido Donor Groups: Diastereoselective Synthesis of 1-Cyclopropane α-Amino Acids

Warming of 4-phthalimido-N-mesyl-1,2,3-triazole in the presence of alkenes followed by silica gel induced hydrolysis results in a highly diastereoselective and catalyst-free entry to N-phthalimidocyclopropanecarboxaldehydes.

Operando Studies of the Catalytic Hydrogenation of Ethylene on Pt(111) Single Crystal Surfaces

The hydrogenation of ethylene on Pt(111) single-crystal surfaces was studied by combining measurements of the kinetics of reaction using mass spectrometry detection with the simultaneous characterization of the species present on the surface using reflection–absorption infrared spectroscopy. The kinetics measured by us matches past reports on the same system, with zero- and first-order dependence on the partial pressures of ethylene and hydrogen, respectively, and extensive H–D exchange if D2 is used instead of H2. The reaction takes place in the presence of an alkylidyne surface layer, which forms immediately upon exposure of the clean surface to the reaction mixture and can be removed by hydrogen or another olefin but at rates 1–2 orders of magnitude slower than the ethylene-to-ethane conversion. The nature of the alkylidyne surface species changes slightly upon being exposed to high pressures of hydrogen, with the carbon in the terminal methyl moiety acquiring some sp2 character. Moreover, the alkylidyne hydrogenation rate shows an inverse relationship with H2 pressure and is reduced by the presence of olefins in the gas phase. Turnover frequencies for the olefin hydrogenation reaction under pressures in the Torr range are high, as reported repeatedly in the past, but the corresponding reaction probabilities are quite low, below the 10–4 range. In contrast, almost unit reaction probability was observed here in effusive collimated molecular beam experiments emulating intermediate pressure conditions.

Modeling ozone formation from alkene reactions using the Carbon Bond chemical mechanism

Predictions of ozone formation, due to oxidation of alkenes in presence of NOx, generated by the Carbon Bond 2005 (CB05) and CB05-TU (CB05 with an updated toluene scheme) condensed chemical mechanisms were tested by simulating 138 environmental chamber experiments carried out in 7 different environmental chambers and by running box modeling with four cases. CB05 and CB05-TU reasonably simulated ozone formation from propene under typical urban conditions and for cases with moderately elevated propene concentrations. Chamber simulations of 47 propene – NOx and 5 isobutene – NOx experiments and box modeling for four cases (1 for propene and 3 for isobutene) showed that the performance of CB05 and CB05-TU in simulating ozone formation from propene and isobutene can be improved by modeling propene and isobutene using the new condensed reactions for propene and isobutene developed in this work. The results of this study indicate that the capability of condensed chemical mechanisms in simulating ozone formation can be improved by (1) examining the relative importance of VOCs based on their emissions and reactivity, (2) separately representing relatively important VOCs in the mechanism, (3) modeling less important compounds using reactions of lumped model species shared by multiple compounds, and (4) evaluating mechanisms with experimental data such as environmental chamber data.

Interconversion of cis‐ and trans‐Fused Oxabicyclo[5.2.0]nonan‐2‐ones

AbstractOn irradiation (350 nm) in the presence of alkenes (2,3‐dimethylbut‐2‐ene, 1,1‐dimethoxyethene, and 2,4,4‐trimethylpent‐1‐ene), benzoxepinone 1 and dioxepinone 2 are converted into mixtures of cis‐ and trans‐fused oxabicyclo[5.2.0]nonan‐2‐ones. Their relative thermodynamic stabilities (as reflected by the observed diastereoisomer ratios after equilibration with basic alumina) depend on the substitution pattern of the alkene moiety.

Effect of trimethylaluminum on the formation of active sites of the catalytic system bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6-tetrafluoroanilinato]titanium(IV) dichloride—MAO and catalytic isomerization of hex-1-ene

The transformations of bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6-tetrafluoroanilinato]-titanium(iv) dichloride (L2TiCl2) occurring in toluene under the action of methylalumoxane (MAO) were studied by 1H NMR spectroscopy. The commercially available MAO containing trimethylaluminum (AlMe3) and MAO free of AlMe3 (the so called “dry” MAO) were used. The catalytic transformations of hex-1-ene involving the systems L2TiCl2-MAO were studied. We proposed the structures of the cationic titanium complexes formed in the absence and in the presence of hex-1-ene under the action of MAO. In the absence of olefin, neutral and cationic titanium complexes are decomposed under the action of AlMe3 according to the exchange reaction of the complex ligand with the methyl groups of AlMe3 to form LAlMe2. The neutral complexes react considerably faster than the cationic ones. In the presence of olefin, decomposition of complexes under the action of AlMe3 is suppressed. The titanium complex activated by “dry” MAO isomerizes hex-1-ene to hex-2-ene. In the presence of large amounts of TMA (commercial MAO), this reaction does not take place.

Polyoxometalate-based hybrid mesostructured catalysts for green epoxidation of olefins

Novel hybrid polyoxometalates (POM) of α-H3PW12O40·nHMPA and α-H3PMo12O40·nHMPA composed of α-H3PW12O40 and H3PMo12O40 heteropoly acides (HPAs) and hexamethylphosphoramide (HMPA) organic substrate has been synthesized and purified. SBA-15 mesoporous silica is synthesized, using P123 surfactant via hydrothermal method, and functionalized with aminopropyl functional groups via grafting method. The synthesized mesostructured supports are used for intercalation of the hybrid POMs. The parent Keggin HPAs are also immobilized within the supports to perform closer and more efficient investigation. After characterization, effect of functional groups on immobilization pattern and quality is taken into consideration. The mesostructured organic–inorganic hybrid materials are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic absorption, and FT-IR analysis. The newly designed hybrid catalysts are investigated for heterogeneous epoxidation of olefins. Effects of temperature, oxidant, and catalyst amount are studied and the reaction conditions are optimized. An interpretation of the differences in the catalytic activity of the precursors is put forward and their catalytic activity is compared with their HPA counterparts. Furthermore, effects of functionalization on catalyst activity, stability, and reusability are taken into consideration. Results reveal that the designed mesostructured POM based hybrid catalysts can selectively and efficiently epoxidize olefins in presence of hydrogen peroxide as oxidant. The catalysts are shown to be heterogeneous and reusable without significant loss of activity in the proceeding rounds.

Application of a Fluidized Bed Reactor in the MTO (Methanol to Olefin) Process: Preparation of Catalyst and Presentation of a Kinetic Model

Light olefins are basic raw materials for petrochemical industries and the global demand for the latter is growing. The authors investigated the conversion of methanol to light olefins in presence of acidic SAPO-34 molecular sieve as the reaction catalyst. SAPO-34 was synthesized by hydrothermal method, applying morpholine as the template. The molecular sieve was then changed into protonated form by ion exchange process with ammonium chloride at 80°C. A kinetic study was carried out within the temperature range of 375–425°C and 4 bar pressure using a differential fixed bed reactor. An appropriate kinetic model was presented and the kinetic parameters were evaluated as functions of temperature. In addition, the formation of light olefins was implemented in a fluidized bed reactor under a wide range of operating conditions. The experimental results were correlated with those predicted from a hydrodynamic model. Taguchi's experimental design method was applied to determine the optimum operating parameters of this process conducted in the fluidized bed reactor. The optimized parameters were the following: temperature = 425°C; ratio of inlet gas velocity to minimum fluidizing velocity (U0/Umf) = 7; catalyst mean particle size = 240 μm.

ChemInform Abstract: Boric Acid‐Mediated Mild and Efficient Friedel—Crafts Alkylation of Indoles with Nitro Styrenes.

An efficient method has been developed for the synthesis of indole 3-derivatives by the Friedel–Crafts alkylation of indole with nitro olefins in presence of boric acid in aqueous medium.

Stereoselective Single (Copper) or Double (Platinum) Boronation of Alkynes Catalyzed by Magnesia‐Supported Copper Oxide or Platinum Nanoparticles

Copper(II) oxide nanoparticles supported on magnesia have been prepared from Cu(II) supported on magnesia by hydrogen reduction at 400 °C followed by storage under ambient conditions. X-ray photoelectron spectroscopy of the material clearly shows that immediately after the reduction copper(0)-metal nanoparticles are present on the magnesia support, but they undergo fast oxidation to copper oxide upon contact with the ambient for a short time. TEM images show that the catalytically active CuO/MgO material is formed of well-dispersed copper oxide nanoparticles supported on fibrous MgO. CuO/MgO exhibits a remarkable catalytic activity for the monoborylation of aromatic, aliphatic, terminal, and internal alkynes, the products being formed with high regio- (borylation at the less substituted carbon) and stereoselectivity (trans-configured). CuO/MgO exhibits complete chemoselectivity towards the monoborylation of alkynes in the presence of alkenes. Other metal nanoparticles such as gold or palladium are inactive towards borylation, but undergo undesirable oligomerization or partial hydrogenation of the C≡C triple bond. In contrast, platinum, either supported on magnesia or on nanoparticulate ceria, efficiently promotes the stereoselective diborylation of alkynes to yield a cis-configured diboronate alkene. By using platinum as the catalyst we have developed a tandem diborylation/hydrogenation reaction that gives vic-diboronated alkanes from alkynes in one pot.

Assessment of the Moroccan Mediterranean Coasts Contamination by Hydrocarbons (Non Aromatic Hydrocarbons, Aromatic Hydrocarbons and Linear Alkylbenzenes)

In order to evaluate the contamination of the Moroccan Mediterranean coasts by persistent organic pollutants we studied hydrocarbons and linear alkylbenzenes in bivalve tissues (cockles) collected seasonally from several points along the western Moroccan coasts in the Mediterranean Sea. Two fractions corresponding to non aromatic and aromatic hydrocarbons were analyzed by GC/FID and GC/MS. Non aromatic hydrocarbon concentrations vary in the range of 24.1 - 2731 μg/g dry weight (dw) while total n-alkanes vary from 2.2 to 68.2 μg/g. Few exceptions were noted with values up to 243 μg/g (dw), which is high compared to other Mediterranean sites. The presence of an important unresolved complex mixture (UCM) indicated a significant petroleum contamination, confirmed by the identification of 17α(H), 21β(H) hopanes. Biogenic contributions were also detected within the n-alkane distribution (n-C17, n-C18, n-C27, n-C29, n-C17/Pr, n-C18/Ph) and by the presence of alkenes. C13 and C14 linear alkylbenzenes were found at concentrations of 478 - 1954 ng/g. and point to pollutant inputs from wastewaters. Polycyclic aromatic hydrocarbons were present in low concentrations below the GC detection limit. The observed seasonal and spatial variations were linked to the magnitude of inputs from marine and land-based pollutant discharges.

Oxidative Cleavage of Alkenes Using an In Situ Generated Iodonium Ion with Oxone as a Terminal Oxidant

A facile and operationally convenient catalytic procedure for oxidative cleavage of alkenes is described. In situ formed [hydroxy(4-carboxyphenyl)iodonium]ion, 2, from the oxidation of 4-iodobenzoic acid, 1, has been shown to facilitate the cleavage of a variety of alkenes in presence of Oxone as a co-oxidant. Optimization of the reaction conditions using 1-phenyl-1-cyclohexene, 3, and the competitive oxidative cleavage of different substrates using the optimized conditions has uncovered important mechanistic details of the reaction.

Boric Acid–Mediated Mild and Efficient Friedel–Crafts Alkylation of Indoles with Nitro Styrenes

An efficient method has been developed for the synthesis of indole 3-derivatives by the Friedel–Crafts alkylation of indole with nitro olefins in presence of boric acid in aqueous medium.

Iron Catalyzed Competitive Olefin Oxidation and ipso-Hydroxylation of Benzoic Acids: Further Evidence for an FeV═O Oxidant

The iron complex [Fe(II)(TPA)(CH(3)CN)(2)](OTf)(2) (1) [TPA = tris(2-pyridylmethyl)amine] with H(2)O(2) as an oxidant performs ipso-hydroxylation of electron-withdrawing benzoic acids at room temperature, leading to multiple turnovers of corresponding phenols. ipso-Hydroxylation competes with olefin epoxidation and cis-dihydroxylation in the presence of olefins, with the product ratios being modulated by the relative amounts of benzoic acid, olefin, and water. It is proposed that benzoic acid and water compete for the available sixth site on the [(TPA)Fe(III)(OOH)] intermediate, which undergoes O-O bond heterolysis to form, respectively, the Fe(V)(O)(O(2)CAr) and Fe(V)(O)(OH) oxidants that determine the product outcome. The putative Fe(V)(O)(O(2)CAr) oxidant decays either by undergoing oxidative decarboxylation and subsequent ipso-hydroxylation to form the observed phenol product or by oxo-transfer to olefins to form epoxide. The observed higher yield of phenol over epoxide or cis-diol in all cases studied, where an electron-withdrawing benzoic acid is present in the reaction mixture, suggests that intramolecular decay of the putative Fe(V)(O)(O(2)CAr) oxidant is favored over intermolecular olefin oxidation. These results support the mechanistic framework postulated for Fe(TPA) oxidative catalysis and further strengthens the notion that oxoiron(V) species are the key oxidants in these reactions.

ChemInform Abstract: Thermal Reactivity of 2-Azido- and 3-Azido-benzo(b)thiophene with Alkenes.

Thermal decomposition of 2-azidobenzo[b]thiophene (2-BTA) in the presence of various (E)-and (Z)-alkenes, at room temperature, affords thiochroman-4-carbonitriles resulting from cycloaddition of an ortho-quinoidal enethione intermediate (2) to the olefin double bonds and/or 1-(2-benzothienyl)aziridines which generally occur in a non-stereospecific fashion. In one case, i.e. with diethyl fumarate, clear-cut spectroscopic and chemical evidence for the intermediacy of a triazoline adduct in the formation of the observed trans-and cis-aziridines has been obtained. In the presence of 1-pyrrolidinyl-cyclopentene or -cyclohexene the azide furnishes an isolated triazoline in quantitative yield, whereas with methyl (E)-3-(N-pyrrolidinylacrylate leads to methyl 1-(2-benzothienyl)triazole-4-carboxylate arising from an intermediate triazoline by readily occurring elimination of pyrrolidine. Results suggest that 2-BTA generally undergoes cycloaddition reactions to give triazoline adducts, from which aziridines can be eventually produced, in competition with unimolecular ring-cleavage fragmentation leading to the enethione (2) probably via concerted ring opening and nitrogen extrusion. Suitable support has been provided by the finding that 3-azidobenzo[b]thiophene (3-BTA) can exhibit analogous cycloaddition reactions with alkenes under the same reaction conditions. The present evidence contradicts our previous claim that a singlet nitrene should be an intermediate in the formation of aziridine and ring-cleavage products arising from decomposition of 2-BTA in the presence of alkenes.

ChemInform Abstract: Photochemical Reactions of Tetrahydroquinoxalin-2(1H)-ones and Related Compound.

Photochemical behaviors of the pyrazinone derivatives 5,6,7,8-tetrahydroquinoxalin-2(1H)-ones 1a–c and 1,5,6,7,8,9-hexahydro-2H-cyclohepta[b]pyrazin-2-one 1d were investigated. Dye-sensitized photo-oxygenation of 1a-c gave the 1:1 adducts 5a–c of the corresponding 3,8a-epidioxy-3,5,6,7,8,8a-hexahydroquinoxalin-2(1H)-one 4 and H2O, whereas 1d gave 3,9a-epidioxy-1,3,5,6,7,8,9,9a-octahydro-2H-cyclohepta[b]pyrazin-2-one 4d (Scheme 2). The different kind of products was interpreted as being the result of the ring strain and steric hindrance of endoperoxides produced from 1a–d with singlet oxygen. Irradiation of 1a–b in the presence of alkenes gave tricyclic azetidine derivatives 9 by [2 + 2] cycloaddition of the CN bond of 1 to the alkene.

ChemInform Abstract: General and Convenient Route to Alkenylidenecyclopropanes: Generation of Alkenylidenecarbenes from 1,1-Dibromocyclopropanes Under Phase- Transfer Conditions.

Alkenylidenecyclopropanes have been prepared in a stereospecific manner by the reaction of 1,1-disubstituted 2,2-dibromocyclopropanes with sodium hydroxide under phase-transfer conditions in the presence of alkenes.

ChemInform Abstract: Oxidation of Diethyl (Pyridylmethyl)malonates with Mn(III) Acetate, Ce( IV) Ammonium Nitrate, and Iron(III) Perchlorate in the Presence of Alkenes and Alkynes.

ChemInform Abstract: Oxidation of Diethyl (Pyridylmethyl)malonates with Mn(III) Acetate, Ce( IV) Ammonium Nitrate, and Iron(III) Perchlorate in the Presence of Alkenes and Alkynes.