Bio-oil production from Onopordum acanthium L. by slow pyrolysis

In this study, the usability of the plant thistle, Onopordum acanthium L., belonging to the family Asteraceae (Compositae), in liquid fuel production has been investigated. The experiments were performed in a fixed-bed Heinze pyrolysis reactor to investigate the effects of heating rate, pyrolysis temperature and sepiolite percentage on the pyrolysis product yields and chemical compositions. Experiments were carried out in a static atmosphere with a heating rate of 7 °C/min and 40 °C/min, pyrolysis temperature of 350, 400, 500, 550 and 700 °C and particle size of 0.6 < D_p < 0.85 mm. Catalyst experiments were conducted in a static atmosphere with a heating rate of 40 °C/min, pyrolysis temperature of 550 °C and particle size of 0.6 < D_p < 0.85 mm. Bio-oil yield increased from 18.5% to 27.3% with the presence of 10% of sepiolite catalyst at pyrolysis temperature of 550 °C, with a heating rate of 40 °C/min, and particle size of 0.6 < D_p < 0.85 mm. It means that the yield of bio-oil was increased at around 48.0% after the catalyst added. Chromatographic and spectroscopic studies on the bio-oil showed that the oil obtained from O. acanthium L. could be used as a renewable fuels and chemical feedstock.     

Microwave-assisted cycloadditions of 2-alkynylbenzonitriles with sodium azide: selective synthesis of tetrazolo[5,1-a]pyridines and 4,5-disubstituted-2H-1,2,3-triazoles

Under microwave irradiation (75 W), treatment of 2-alkynylbenzonitriles with 1.5 equiv of sodium azide in DMSO at 140 °C gave 4,5-disubstituted-2H-1,2,3-triazoles in 60-99% yields. Additionally, adding 8 equiv of ZnBr₂ and using 8 equiv of sodium azide in DMF at 100 °C lead to the formation of tetrazolo[5,1-a]isoquinolines up to 87% yield.     

Stereoselective Heck arylation of a functionalized cyclopentenyl ether using (S)-N-methyl-pyrrolidine as the stereochemical controller

The study of a series of palladium(0)-catalyzed C2-arylations of a 1-cyclopentenyl ether equipped with a chiral (S)-N-methyl-pyrrolidine auxiliary is reported. Stereoselective Heck monoarylations were performed using aryl iodides under classical heating conditions for 1.7-3.0 h at 80 °C and in one case using 30 min of microwave irradiation at 110 °C. To further explore the scope and nature of this stereoselective methodology, aryl bromides were also utilized as arylating agents, using 20 min of microwave processing at 120-130 °C. High to excellent diastereopurities (90-98% de) were obtained according to ¹H NMR and GC-MS analyses. The prolinol fragment apparently controlled the diastereoselectivity of the Heck reaction by presenting the arylpalladium species from the preferred side of the double bond. By X-ray structure diffraction analysis of an N-quaternized Heck product, the absolute configuration of the new stereocenter was established as (R), supporting a Si-face migratory insertion.     

Microwave-assisted rapid and efficient synthesis of C-alkyl imidazoisoquinolinone derivatives

The synthesis of a set of 10-benzyl-2,3-dihydroimidazo[1,2-b]isoquinolin-5(1H)-one and 5-oxo-imidazo[1,2-b]isoquinolin-10-yl)-N-phenylacetamide derivatives was achieved by exposing the corresponding alkylating agent and imidazoisoquinolinone to microwave irradiation and traditional oil bath heating in the presence of K₂CO₃ and DMAP. The microwave technique as well as DMAP as base accelerated the alkylation reaction for 2-6 min giving 79-88% yields.     

Synthesis of 7-aryl-1,8-naphthyridines via addition of aryl boronic acids to 1,8-naphthyridine N-oxides

Simply combining aryl boronic acids with 1,8-naphthyridine N-oxides and heating at 110 °C in toluene or dimethylformamide affords the corresponding 7-aryl-1,8-naphthyridines. The reaction is not sensitive to air or moisture and the process can be extended to other electron-deficient heteroaromatic N-oxides.     

Formation of γ-Fe2O3 nanoparticles and vacancy ordering: An in situ X-ray powder diffraction study

The formation of maghemite, γ-Fe₂O₃ nanoparticles has been studied by in situ X-ray powder diffraction. The maghemite was formed by thermal decomposition of an amorphous precursor compound made by reacting lauric acid, CH₃(CH₂)₁₀COOH with Fe(NO₃)₃·9H₂O. It has been shown that cubic γ-Fe₂O₃ was formed directly from the amorphous precursor and that vacancy ordering starts about 45 min later at 305 °C resulting in a tripled unit cell along the c-axis. The kinetics of grain growth was found to obey a power law with growth exponents n equal to 0.136(6) and 0.103(5) at 305 and 340 °C, respectively. Particles with average sizes of 12 and 13 nm were obtained in 86 and 76 min at 305 and 340 °C, respectively. The structure of cubic and vacancy ordered phases of γ-Fe₂O₃ was studied at 305 °C by Rietveld refinements.     

A one-pot synthesis of 2,3-dihydro-1H-pyrrolo[3,2-c]quinolines

A one-pot synthesis of the 2,3-dihydro-1H-pyrrolo[3,2-c]quinoline core from substituted 2-iodoanilines and 2,3-dihydro-1H-pyrrole was achieved using 10 mol % Pd(PPh₃)₄, and K₂CO₃ in 1,4-dioxane at 170 °C for 1 h in a microwave oven. This reaction can be carried out on a gram scale. The proposed mechanism involves a Heck-coupling reaction followed by intra-molecular Schiff base formation and double bond migration.     

Microwave-promoted Suzuki-Miyaura coupling of arylboronic acids with 1-bromo-2-naphthol, o-bromophenol, and o-chlorophenol

In this letter we report a simple and efficient way for the direct Suzuki-Miyaura cross-coupling of unprotected 2-hydroxyaryl bromides and of 2-chlorophenol with arylboronic acids using suitable phosphine/Pd(OAc)₂ catalysts systems with moist K₃PO₄/toluene or moist CsF/dioxane and microwave heating (20 min 105 °C to 3 h 100-120 °C) with an internal temperature control providing 2-hydroxybiaryls in yields up to 98%.     

Solid-state cis-trans isomerization reaction of (η-MeC5H4)W(CO)2P(OPr)3I

cis-(η⁵-MeC₅H₄)W(CO)₂P(OⁱPr)₃I (1) was converted to the trans isomer 2 in the solid state (90-110 °C). The reaction was monitored by heating 1 in NMR tubes for periods of time (2-60 min), cooling the tubes to room temperature and determining the conversion by solution ³¹P and ¹H NMR spectroscopy. The data were consistent with a first-order reaction and yielded an activation energy of 59 ± 3 kJ mol⁻¹. Comparative kinetic data were obtained from an in situ analysis of a powder-XRD study of 1. The powder-XRD study was conducted at 80-100 °C (10-60 min), yielding an activation energy of 52 ± 2 kJ mol⁻¹ (first-order reaction). The reaction could not be monitored by single crystal X-ray diffraction as the crystal disintegrated over time on heating. This disintegration process was monitored by optical microscopy and revealed that while the bulk crystal morphology was retained the crystal surface roughened with time. The compounds 1 and 2 were also structurally characterised by X-ray crystallographic techniques.     

Simple access to pentacyclic oxazinoisoquinolines via an unexpected transformation of aminomethylnaphthols

Unexpected reactions between 1-α-aminobenzyl-2-naphthol, 1-aminomethyl-2-naphthol, N-benzyl-1-α-aminobenzyl-2-naphthol and 6,7-dimethoxy-3,4-dihydroisoquinoline to furnish naphth[1,2-e][1,3]oxazino[2,3-a]isoquinolines are reported. The reaction conditions involved classical heating at 80 °C in MeCN for 22 h (57-62%), or the use of microwave conditions (100 °C), which allowed a reduction of the reaction time to 90 min and resulted in somewhat higher yields (73-82%).     

Palladium-catalyzed C-N bond formation: synthesis of 1-aryl-1H-pyrazoles from β-bromovinyl aldehydes and arylhydrazines

Cyclic and acyclic β-bromovinyl aldehydes are cyclized with an array of arylhydrazines in toluene at 125 °C in the presence of a palladium catalyst and a phosphorus chelating ligand together with NaO^tBu to give 1-aryl-1H-pyrazoles in moderate to good yields.     

On the explosive properties of 1H-benzotriazole and 1H-1,2,3-triazole

For 1H-benzotriazole, no explosive properties are observable, but the relative high exothermic decomposition energy of 1590 J/g should be kept in mind. Nevertheless, an endothermic melting barrier at 100 °C ensures safe handling at lower temperatures. For 1H-1,2,3-triazole, the exothermic decomposition energy is as high as 2600 J/g, but explosive properties are also not detectable. Therefore, both reagents are hazardous with regard to the exothermic decomposition potential and can be handled safely with precautions.     

Stereoselective synthesis of (E)-β-arylvinyl bromides by microwave-induced reaction of anti-3-aryl-2,3-dibromopropanoic acids using an AgOAc-AcOH system

(E)-β-Arylvinyl bromides were stereoselectively prepared in high yields by microwave irradiation of the corresponding anti-3-aryl-2,3-dibromopropanoic acids in AcOH in the presence of AgOAc for 0.5-3.0 min.     

Thermo-Raman spectroscopy in situ monitoring study of solid-state synthesis of NiO-Al2O3 nanoparticles and its characterization

Hyphenation of thermogravimetric analyzer (TGA) and thermo-Raman spectrophotometer for in situ monitoring of solid-state reaction in oxygen atmosphere forming NiO-Al₂O₃ catalyst nanoparticles is investigated. In situ thermo-Raman spectra in the range from 200 to 1400 cm⁻¹ were recorded at every degree interval from 25 to 800 °C. Thermo-Raman spectroscopic studies reveal that, although the onset of formation is around 600 °C, the bulk NiAl₂O₄ forms at temperatures above 800 °C. The X-ray diffraction (XRD) spectra and the scanning electron microscopy (SEM) images of the reaction mixtures were recorded at regular temperature intervals of 100 °C, in the temperature range from 400 to 1000 °C, which could provide information on structural and morphological evolution of NiO-Al₂O₃. Slow controlled heating of the sample enabled better control over morphology and particle size distribution (∼20-30 nm diameter). The observed results were supported by complementary characterizations using TGA, XRD, SEM, transmission electron microscopy, and energy dispersive X-ray analysis.     

Microwave-assisted nickel(II) acetylacetonate-catalyzed arylation of aldehydes with arylboronic acids

Applying sealed vessel microwave heating at 180 °C in toluene the arylation of aromatic and aliphatic aldehydes with arylboronic acids using 1-2 mol % of Ni(acac)₂ as a catalyst can be performed efficiently within 10-30 min providing the desired diarylmethanols or benzyl alcohols in good yields.     

Complex formation equilibria between Ag(I) and thioureas in n-propanol

Complex formation equilibria between Ag(I) and thiourea or N-alkyl-substituted thioureas have been investigated in n-propanol by potentiometry at 10 °C intervals from 5 to 50 °C. Stepwise formation of tris-coordinated AgL_n (n = 1-3) complexes has been found for the majority of the ligands. ΔH and ΔS values for the complex formation reactions have been evaluated from the dependence of ln β_n on temperature. The alkyl-substituents affect the ligand affinities in different ways in relation with the coordination level n.The reactions are exothermic with few exceptions. Enthalpy favoured complex formation with negative dependence of ΔG on temperature (ΔS > 0) have been found.The enthalpy and entropy changes for the stepwise complex formation equilibria are correlated by two linear compensative relationships with the same isoequilibrium temperature 50-51 °C.     

Microwave-assisted rapid and straightforward synthesis of 2-aryl-4-quinolones from acylated 2′-aminoacetophenones

The syntheses of a diverse set of 2-aryl-4-quinolone derivatives were achieved by exposing corresponding acylated 2′-aminoacetophenones to microwave irradiation in the presence of NaOH. The microwave accelerated cyclizations were complete within 10-22 min at 120 °C giving 57-95% isolated yields.     

Microwave-assisted benzyne-click chemistry: preparation of 1H-benzo[d][1,2,3]triazoles

The benzotriazoles were prepared by three-component and two-component microwave-assisted [3+2] cycloadditions of various azides to benzyne, 3-methoxybenzyne, and 4,5-difluorobenzyne. In the three-component reaction, the aryne is generated, in the presence of an azide prepared in situ, by the reaction of an o-(trimethylsilylaryl) triflate with either CsF or KF/18-Crown-6. However, in the two-component reactions, a freshly prepared azide is added to the reaction vessel prior to aryne generation. Good to excellent yields of benzotriazoles were obtained in 15-20 min when the microwave-assisted reactions were carried out at 125 °C. These reaction times are significantly faster than similar reactions carried out using conventional heating.     

An efficient one-pot, two-step synthesis of 4-substituted 1-heteroarylpiperazines under microwave irradiation conditions

A highly efficient one-pot, two-step microwave procedure has been developed for the synthesis of 4-substituted 1-heteroarylpiperazines. Microwave heating of heteroaryl chlorides with 1,4-diazabicyclo[2.2.2]octane (DABCO) at 160 °C for 15 min yielded 1-heteroaryl-4-(2-chloroethyl)piperazines, which could be further reacted with various nucleophiles, again under microwave irradiation conditions, to give an array of 4-substituted 1-heteroarylpiperazines in good to excellent yields.